USMLE Pediatry For Student Diagnostic Pédiatrie P1 200 QCM

1) An African-American boy is in the newborn nursery with a bulge on his abdomen that was identified immediately after birth and is most pronounced during crying. The patient was born to an 18-year-old woman who did not receive prenatal care or take prenatal vitamins. Vitals are normal. Examination shows a soft swelling at the umbilical ring. Which of the following is the most likely diagnosis and best course of action for this patient?

2) A 14-year-old girl is brought to the physician’s office because of irregular menstrual periods. She had her menarche at age 13, and since then her periods have been irregular with the cycles varying from 3 to 6 weeks. She has no other symptoms. Physical examination is unremarkable. She has age appropriate secondary sexual characteristics. A urine pregnancy test is negative. Serum prolactin and thyroid stimulating hormone levels are normal. Administration of micronized oral progesterone results in withdrawal bleeding in 3 days. Which of the following most likely explains her irregular periods?

3) Parents bring their 17-year-old son to the emergency department due to his strange behavior at times during the past few weeks. The boy is normally polite and soft-spoken, but he has recently become irritable, impatient, and rude. His parents initially dismissed his behavior as a “phase” with the expectatioin that he would grow out of it. However, they became very concerned on discovering that he had stolen money from their wallets and was sleeping erratically. When questioned by his father about his strange behavior, the boy responsed, “I’m on a secret mission. The king of Norway has sent me here to spy on the US government.” His temperature is 36.6 C, BP is 144/94 mmHg, pulse is 118/min, and respirations are 18/min. On physical examination, the patient appears to be irritated. He is sweating profusely and his pupils are dilated. He is observed in the emergency department for several hours, his condition improves, and he is discharged to the care of his parents. Which of the following is the most likely diagnosis?

4) A 10-year-old boy presents to the emergency room with chief complaints of fever and increasing fatigue. He was well until 2 weeks ago when he had an upper respiratory illness (URI). He has a decreased appetite and has lost 2 lbs over the last 2 weeks. He has some shortness of breath when he climbs the stairs. His past medical history is unremarkable. On examination his vital signs are normal, and his height and weight are at the 80th percentile. His conjunctiva are pale, and he has bilateral, mobile (about 1-2cm) and non-tender nodes in the cervical, axillary, and inguinal regions. Hepatosplenomegaly is present, and skin shows no lesions. Labs are Hemoglobin 7.3g/dl, platelet count 20,000/mm3, WBC count 42,100/mm3, with 24% lymphoblasts, 70% lymphocytes, and 6% atypical lymphocytes. Chest X-rays show clear lung fields but a wide mediastinum. Which of the following is the most likely diagnosis in this patient?

5) A 7-year-old boy is referred by his school for psychiatric evaluation. The teachers have noticed that, in the past year, he has been unable to sustain attention in class, and has been fidgeting and talking to his peers during class. He seems unable to wait for others to finish speaking and keeps interrupting and blurting out answers before questions are completed. At home, his parents state that he is forgetful and losses things easily. Which of the following is the most likely diagnosis?

6) An 8-year-old boy falls on his right hand with the arm extended, and he breaks his elbow by hyperextension. X-ray films show a supracondylar fracture of the humerus. Which of the following complications is of greatest concern with this type of injury?

7) An 18-year-old girl has hepatosplenomegaly, an intention tremor, dysarthria, dystonia, and deterioration in her school performance. She also developed abnormal urine with excess glucose, protein, and uric acid. She has a several-year history of elevated liver enzymes of unknown etiology. Which of the following best explains her condition?

8) The 7-year-old boy now in your office was last seen 2 weeks ago with a mild viral upper respiratory tract infection. Today, however, he presents with fever, ataxia, weakness, headache, and emesis. In the office he has a 3 minutes left-sided tonic-clonic seizure. You send him to the hospital and order a magnetic resonance imaging (MRI) of the brain, the results of which show disseminated multifocal white matter lesions that enhance with contrast. This boy’s likely diagnosis is which of the following?

9) A 15-year-old girl presents to a pediatric cardiology clinic with a complaint of chest pain. She states the pain has come and gone over the past year, but has increased in frequency over the past few weeks. She describes it as a sharp pain over her left chest. Physical examination reveals a healthy-appearing 15-year-old girl. Her temperature is 37.2 C (99 F), pulse is 90/min, and respiratory rate is 20/min. Lung examination is normal. Cardiac examination reveals a late systolic murmur preceded by a click at the apex. No heave or rub is present. An electrocardiogram and chest x-ray film are unremarkable. Which of the following is the most likely diagnosis?

11) A 1-year-old Caucasian boy is brought to your office with necrotic periodontal infection. The past medical history is significant for recurrent cutaneous and sinus infections revealing S. Aureus and P. Aeruginosa isolates. The separation of the umbilical cord was delayed (4 weeks). CBC shows leukocytosis and increased neutrophils. The number of peripheral lymphocytes is normal. Gamma-globulin level is increased on plasma protein electrophoresis. The Nitroblue tetrazolium (NBT) test is normal. Which of the following is the most likely defect present in this patient?

12) A 2-year-old girl is brought to the emergency department due to severe, sudden-onset abdominal pain. She has nausea and vomiting, and her stools contain blood and mucus. Her parents say that she was in her usual state of health when she developed this problem. Her pulse rate is 116/min, blood pressure is 90/60mm Hg, temperature is 37.7C (100F), and respirations are 28/min. She looks lethargic and ill. She is crying and drawing her knees towards her chest. Her abdomen is tender to palpation, and there is a palpable, sausage-like abdominal mass. The bowel sounds are increased, and rectal examination reveals bloody mucus. What is the most likely cause of her symptoms?

13) A 9-year-old boy presents with a 3-month history of multiple episodes of sudden awakening at night. His mother states that when he wakes up suddenly, he screams, "Go! Get away! Go!" and does not respond to the parents. His eyes are wide open, and he sweats heavily and looks scared. The parents have had to struggle to awaken him. After the episodes, he has no memory of what happened. Which of the following is the most likely diagnosis?

14) A 16-year-old girl presents with lower abdominal pain and fever. On physical examination, a tender adnexal mass is felt. Further questioning in private reveals the following: she has a new sexual partner; her periods are irregular; she has a vaginal discharge. Which of the following is the most likely diagnosis?

15) A 6-year-old girl with acute lymphocytic leukemia (ALL) is admitted to the hospital with a generalized vesicular rash and high fever. She has no previous history of chickenpox and has never received immunization for varicella. Her 4-year-old sister recently recovered from chickenpox that started about 10 days ago. On admission, her temperature is 38.4 C (101.1 F), blood pressure is 94/58 mm Hg, pulse is 80/min, and respirations are 20/min. Which of the following is the most serious complication of varicella that might occur in this patient?

16) An 18-year-old male college student is seen in the student health clinic for urinary frequency, dysuria, and urethral discharge. Which of the following is likely to explain his condition?

17) A 1-year-old girl is brought to the emergency department by her mother because the child's "eyes and feet are dancing." On physical examination, the girl is well developed and in no acute distress. Her temperature 37.0 C (98.6 F), blood pressure is 100/55 mm Hg, pulse is 100/min, and respirations are 20/min. The patient has opsoclonus, myoclonus, and ptosis of the right eye. On history, the mother notes the child was born "looking like a blueberry muffin" and has had a persistent cough since the age of 2 months. Which of the following is the most likely diagnosis?

18) A 15-day-old male infant is brought to the emergency department by his mother due to vomiting and bloodstained stools since yesterday. The vomitus is green. Recently, the neonate has been feeding poorly. His birth history is not significant: he was absolutely normal and passed meconium within the first 12 hours of life. He has been breastfed since birth. His pulse rate is 122/min and blood pressure is 80/50mm Hg. He is irritable, his mucous membranes are dry, and his abdomen is distended. Based on these findings, what is the most likely diagnosis?

19) A married couple brings their 2-week-old infant to the office for the evaluation of lethargy, poor feeding and hypotonia. The infant was "fine" until yesterday, when he started to present with these symptoms. The mother's medical history is unremarkable, and her pregnancy was uneventful. On examination, hypotonia, poor reflexes and bulging fontanel are noted. There are no focal neurological signs. He is hypotensive and tachycardiac. His temperature is 39.4 C (103F). Initial investigation reveals a WBC count of 16,000/mm3 with 18% bands. What is the most likely diagnosis?

20) A 5-week-old infant is brought to the clinic for a 4-week history of noisy breathing that has not improved. She has otherwise been healthy except for a current upper respiratory infection for the past 4 days, which according to the parents, has worsened the noisy breathing. On examination, she has inspiratory stridor. The noisy breathing improves when the infant is asleep. Which of the following is the most likely diagnosis?

21) A 1-day-old infant who was born by a difficult forceps delivery is alert and active. She does not move her left arm spontaneously or during a Moro reflex. Rather, she prefers to maintain it internally rotated by her side with the forearm extended and pronated. The rest of her physical examination is normal. This clinical scenario most likely indicates which of the following?

22) A 2-year-old girl is brought to the physician because of protracted irritability, crying, and loss of appetite. She recently had a sore throat. Her temperature is 38.5 C (101.3 F). Physical examination is unremarkable, except for abnormalities of the tympanic membrane detected on otoscopic examination. Which of the following signs or symptoms correlates best with a diagnosis of acute otitis media?

23) A 5-year-old boy is brought to the emergency department with high-grade fevers, irritability, dyspnea and difficulty swallowing that started just hours ago. His mother reports that he had been well before going to bed, but then awoke in the middle of the night with respiratory distress. His vaccination history is uncertain. On physical examination, his temperature is 39. 1 °C (102 .4°F), pulse is 130/min, and respirations are 46/min. He appears anxious and restless, and he is drooling. While observing his respirations, you note that inspiring causes him particular distress. There is no stridor. Sitting upright with his neck hyperextended seems to give the child some relief. Which of the following is the most likely diagnosis?

24) A 3-year-old boy is brought to the clinic due to an abdominal mass that his mother noted while she was bathing him. She seems distressed about the matter, and seeks your "expert opinion." The patient does not have any significant past medical history. On examination, he is calm and quiet. A firm abdominal mass is palpated in the left quadrant, which does not cross the midline. The mass is tender on deep palpation, but is not pulsatile Urinalysis reveals a trace amount of blood. What is the most likely diagnosis?

25) A pediatrician is called to the delivery room because a full-term infant has developed cyanosis and respiratory distress immediately after birth. A brief examination of the infant reveals cyanosis on room air not completely relieved by oxygen administered by mask, subcostal and intercostal retractions, absent air entry on the left with audible bowel sounds in the left chest, and poor air entry on the right chest. The heart is best heard in the right hemithorax; the abdomen is flat without organomegaly. Which of the following is the most likely diagnosis?

26) A 5-year-old child develops an earache, but her mother is too busy to take her to the pediatrician. Two weeks later, the child still has not improved and now has a painful, swollen, red area behind the pinna. At this point, the child is taken to the emergency department, where the physician additionally notes the presence of fever and a creamy discharge in the ear canal. Which of the following is the most likely diagnosis?

27) A 3-day-old newborn is ready to be discharged from the neonatal nursery, when his mother reports that a rash has appeared on his abdomen and chest. He otherwise appears healthy. He has no fever and no risk factors for infection. Examination reveals a nontoxic neonate with erythematous papules and vesicles surrounded by patches of erythema. Microscopic evaluation of the pustules reveals numerous eosinophils. What is the most likely diagnosis?

28) An athletic 12-year-old boy complains of left knee pain when he runs and plays sports. The pain resolves when he rests. He has otherwise been well. His physical examination is normal, except for swelling and increased prominence over the left tibial tubercle. A radiograph of the left knee is normal. Which of the following is the most likely diagnosis?

30) A 14-month-old male infant presents to the emergency room with a chief complaint of high grade fever with no response to antipyretic therapy. This illness started suddenly with the abrupt onset of fever early yesterday morning. He then developed a severe cough and increased work of breathing. The mother reports that he is frequently ill. He was hospitalized 2 months ago for pneumococcal pneumonia. On examination: PR: 145/min; RR: 55/min; BP 100/60mm Hg; oxygen saturation 91%; weight 7 kg (154 lbs). He is listless, tired, and small for age. Both ear canals contain purulent drainage. An immunologic work-up is done and found to have markedly elevated IgM, undetectable IgG and IgA with diminished total B-lymphocytes and neutrophils. Which of the following is the most likely diagnosis?

31) A 4-year-old girl is brought to the office due to easy bruising and a rash for the past 3 days. She had an upper respiratory infection approximately two weeks ago. She has never had palpable bruises, hemarthroses, or deep muscle bleeding in the past. She has 2 older brothers, neither of which has had bleeding symptoms before. Her family history is negative for any bleeding disorders. Her vital signs are normal. Physical examination reveals a diffuse petechial rash on her neck, trunk, extremities and groin. There is no hepatosplenomegaly. Nonpalpable ecchymoses of varying ages are present on the shins and arms. The laboratory findings are as follows: Hemoglobin 12 .8 g/dl, Hematocrit 38.5%, WBC 6,000/mm3, Platelets 5,000/mm3, PT 12.0 sec, PTT 30 sec. Peripheral smear shows normal morphology of the red and white blood cell lines. The platelets are reduced in number, and majority of them are increased in size. What is the most likely diagnosis?

32) On the second day after birth, a mother reports that her newborn infant does not move his left hand and his left eyelid droops. On examination, you confirm the findings of the mother and elicit myosis in the left eye. Pregnancy was uneventful, and delivery uncomplicated. Which of the following is the most likely diagnosis?

33) During a physical examination for participation in a sport, a 16-year- old girl is noted to have a late apical systolic murmur, which is preceded by a click. The rest of the cardiac examination is normal. She states that her mother also has some type of heart “murmur” but knows nothing else about it. Which of the following is the most likely diagnosis?

34) A 4-year-old boy is brought to the office for a routine exam. He has a small face, upslanting palpebral fissures, a speckled iris, and a simian crease. Auscultation reveals a loud P2. His mother informs you that he has trisomy. What is the most likely congenital heart disorder in this patient?

35) An 8-year-old boy is brought to the pediatrician with a rash on his abdomen. The mother first noticed the rash about 3 weeks ago. The boy has no fever or other symptoms. On examination, there is a well-circumscribed, circular, erythematous, scaly annular patch on his abdomen. The border of the skin lesion is raised and well defined. Which of the following is the most likely diagnosis?

36) A 16-year-old arrives to your office soon after beginning basketball season. He states that he has had progressive pain in his knees. A physical examination reveals, in addition to tenderness, a swollen and prominent tibial tubercle. Radiographs of the area are unremarkable. Which of the following is the most likely diagnosis?

37) A 3-year-old girl is brought to the physician's office for a routine physical examination. Her facial appearance, short stature, short webbed neck and widely spaced nipples are suggestive of a chromosomal abnormality, which is subsequently confirmed by karyotyping. What is the cardiovascular anomaly that is most likely to be present in this child?

38) A neonate develops severe cyanosis that begins within minutes of birth. Blood drawn one hour after birth shows metabolic acidosis with respiratory acidosis. A chest x-ray film shows a narrow base to the great vessels and the heart resembles an egg on its side. ECG is normal. Which of the following is the most likely diagnosis?

39) A 13-year-old boy is seen for right knee pain that has persisted for the past 2 months despite the use of over-the-counter analgesics. His mother states that he has been limping since he started to have the pain. The pain is of insidious onset, but its intensity sometimes suddenly increases. On physical examination, the boy is obese; his weight is higher than the 90th percentile. Flexion of the right hip causes marked outward rotation and reproduces the pain. Internal rotation of the right hip is limited, and the right leg is slightly shortened compared with the left leg. Which of the following is the most likely diagnosis?

40) A 2-week-old male infant is brought to the office by his mother due to fever and vomiting for the past two days. He appeared normal until two days ago. He is being breastfed. He was born at 32 weeks gestation and weighed 2.7kg (6 Ib) at birth. On examination, he is ill-looking, lethargic, and febrile. His abdomen is distended, bowel sounds are absent, and stool is guaiac-positive. An abdominal x-ray demonstrates pneumatosis intestinalis. What is the most likely diagnosis of this patient?

42) The parents of a 5-year-old boy come to the physician concerned about their child's recurrent leg pains. The boy has been complaining for several weeks about pain in both legs, usually occurring soon after going to bed. He derives relief from rubbing his legs and knees. He does not limp and is able to participate in sports activities. Which of the following is the most likely diagnosis?

43) A young black male with sickle cell trait is preparing for his travel to West Africa from North America. While obtaining his visa, he is advised by the health inspector to obtain some immunizations, although his chances of getting a certain tropical disorder are low. What disease has the sickle cell trait been shown to convey protection against?

44) A 5-year-old boy is brought to the emergency department by his mother. One week ago, he developed a low grade fever followed by persistent bouts of coughing that last 20-30 minutes each. The coughing spells are severe, unresponsive to antitussive medications, and appear to worsen with eating and drinking cold liquids. On physical examination, there is subconjunctival hemorrhage and extensive subcutaneous emphysema over the anterior chest. What is the most likely organism responsible for this child's illness?

45) A one-week-old infant is admitted to the neonatal intensive care unit due to vomiting, abdominal distension, and poor feeding. His vomitus is bile-stained. There is frank blood in his stools. He has been formula- fed since birth. Physical examination shows diminished bowel sounds. Abdominal x-rays reveal dilated loops of bowel with intramural air Laboratory studies show elevated WBCs. What is the most likely diagnosis?

46) A child has a 2-week history of spiking fevers, which have been as high as 40°C (104°F). She has spindle-shaped swelling of finger joints and complains of upper sternal pain. When she has fever, the parents note a faint salmon-colored rash that resolves with the resolution of the fever. She has had no conjunctivitis or mucositis, but her heart sounds are muffled and she has increased pulsus paradoxus. Which of the following is the most likely diagnosis?

47) In the newborn nursery it is noted that a child has uneven gluteal folds. Physical examination of the child's hips reveals that one of them can be easily dislocated posteriorly with a jerk and a "click," and returned to normal position with a "snapping" sound. The family is concerned because a previous child had the same problem. Which of the following is the most likely diagnosis?

48) A cyanotic newborn is suspected of having congenital heart disease. He has an increased left ventricular impulse and a holosystolic murmur along the left sternal border. The ECG shows left-axis deviation and left ventricular hypertrophy (LVH). Which of the following is the most likely diagnosis?

49) A 3-day-old infant with a single second heart sound has had progressively deepening cyanosis since birth but no respiratory distress. Chest radiography demonstrates no cardiomegaly and normal pulmonary vasculature. An ECG shows an axis of 120°and right ventricular prominence. Which of the following congenital cardiac malformations is most likely responsible for the cyanosis?

50) A 2-year-old child is brought to the office due to vomiting. He is recovering from an upper respiratory infection, which was treated by his mother with over-the-counter aspirin. On examination he is irritable, lethargic, agitated and uncooperative. His height, weight and head circumference are at the 50th percentile. The pupils are equal and have a sluggish reaction to light. The sclera is non-icteric. The neck is supple and without adenopathy. The abdomen is flat, with normal bowel sounds. The lab findings are as follows: Serum bilirubin Normal, Serum ASAT and ALAT Increased, Serum ammonia Increased, Prothrombin time Prolonged. A CT scan of the brain shows cerebral edema. CSF analysis is normal, except for increased pressure. What is the most likely diagnosis?

51) A 1-month-old baby boy has bloody diarrhea. No infectious agent is identified, but the baby is found to be profoundly thrombocytopenic. The baby is also noted to have a skin rash, and a dermatologist diagnoses eczema. By three months of age, the baby begins to develop recurrent respiratory infections. If this child survives until adolescence, he is at particularly high risk of developing which of the following?

52) An ill-appearing 2-week-old baby girl is brought to the emergency room. She is pale and dyspneic with a respiratory rate of 80 breaths per minute. Heart rate is 195 beats per minute, heart sounds are distant, a gallop is heard, and she has cardiomegaly on x-ray. An echocardiogram demonstrates poor ventricular function, dilated ventricles, and dilation of the left atrium. An ECG shows ventricular depolarization complexes that have low voltage. Which of the following is the most likely diagnosis based on this clinical picture?

53) A newborn infant has mild cyanosis, diaphoresis, poor peripheral pulses, hepatomegaly, and cardiomegaly. Respiratory rate is 60 breaths per minute, and heart rate is 250 beats per minute. The child most likely has congestive heart failure caused by which of the following?

54) A healthy 7 -year-old Caucasian boy is brought to the office by his mother because of fever and pain in the ear. He has had these symptoms for the past three days. He has no other medical problems. Family history is not significant. He takes no medication. His temperature is 38.3 C (101 F). Otoscopic examination reveals an ear discharge, and the tympanic membrane is immobile with insufflation. He has a boil just behind the pinna of the involved ear. His WBC count is 12,000/mm3. He is diagnosed with otitis media. Which of the following is most specific for the diagnosis of otitis media?

55) A 3 year old male has sudden onset of dry cough with a small amount of bright red blood produced when he coughs. He has had no fevers, runny nose, or vomiting. In the Emergency Department a chest x-ray shows hyperexpansion of the right lung and clear lung fields. Which of the following is the most likely etiology of this child's symptoms?

56) A female neonate is undergoing an examination after birth. She was born to a 33-year-old primigravid mother at term via a normal spontaneous vaginal delivery. The pregnancy was uncomplicated, except for a positive maternal group B Streptococcus culture at 36 weeks' gestation, for which the mother received penicillin during labor. The infant's APGAR scores are 8 at 1 minute and 9 at 5 minutes. The mother notices that the infant has prominent labia and a dull pink vaginal epithelium. Which of the following is the most likely cause of the appearance of the infant's genitalia?

57) A 2-year-old boy presents to the emergency department with fever, irritability, and a skin rash 5 days after the onset of an upper respiratory infection. On examination, his temperature is 39.8 C (103.6 F), and his pulse is 94/min. There is an erythematous skin rash that involves his face, chest, back, and upper extremities. His skin is very tender to touch. Rubbing the skin causes separation of the epidermal layer. Which of the following is the most likely diagnosis?

58) A 9-year-old girl is brought by her sister to her pediatrician with the complaint of severe, intermittent headaches for the past several months, one of which resulted in her going to the ER. The physical examination today, including a careful neurologic examination, is normal. The headache is diffuse, throbbing, lasts several hours, and is not associated with vomiting or other symptoms. The child cannot feel the headaches coming on; they appear on all days of the week; and usually the headaches are gone when she awakens from a nap. The child reports that she is doing well in school, plays clarinet in the school band, and has “lots of friends.” The sister is not sure, but she thinks their father, who lives in another state, may have headaches. The most likely explanation for this girl’s headache is which of the following?

59) Examination of the cerebrospinal fluid (CSF) of an 8-year-old, mildly febrile child with nuchal rigidity and intermittent stupor shows the following: WBCs 85/μL (all lymphocytes), negative Gram stain, protein 150 mg/dL, and glucose 15 mg/dL. A computed tomographic (CT) scan with contrast shows enhancement of the basal cisterns by the contrast material. Which of the following is the most likely diagnosis?

60) A full term neonate is being evaluated following an uncomplicated pregnancy and delivery on day 1 of life. He weighs 3.6kg (8ib), is 20in (50.8cm) tall, and has a head circumference of 13.5in (34cm). His physical examination is unremarkable. Initial laboratory data is shown below. Complete blood count: Hemoglobin 20g/L, Hematocrit 73%, Platelets 200,000/mm3, Leukocyte count 5,500/mm3, Neutrophils 56%, Eosinophils 1%, Lymphocytes 33%, Monocytes 10%. Which of the following findings is most likely to be detected in this neonate?

61) An 8-year-old boy is brought to the emergency department with a head injury. He hit his head on the ground when he fell off his bicycle. He was not wearing a helmet at the time. There was no loss of consciousness. He vomited 2 times after the accident and now complains of a right-sided headache and inability to hear with his right ear. There is no photophobia or diplopia. On physical examination, his blood pressure is 110/72 mm Hg, pulse is 104/min, and respirations are 22/min. He is alert and oriented and responds appropriately to questions. There is a round hematoma on the right side of his head. Bloody drainage is noted from his right ear. Which of the following injury is most consistent with these findings?

62) A 16-year-old girl comes to the physician's office because she has not begun menstruating yet. Both her mother and an older sister started menstruation at age 12. She takes no medication and denies strenuous exercise or excessive dieting. Her height is at the 50fh percentile for age; her weight is at the 60fh percentile. Both her breast and pubic hair development are at Tanner stage 4. Pelvic ultrasonography reveals a normal uterus and ovaries. Which of the following is the most likely diagnosis?

63) A 12-year-old boy presents with a 2-month history of recurrent headache and deteriorating school performance. Neurologic examination is unremarkable except for bitemporal deficits in his visual field. X-ray and MRI of the head are performed. X-ray films show calcifications in the suprasellar region, while MRI images reveal a multicystic tumor displacing the optic chiasm. The patient undergoes neurosurgical operation for excision of the tumor. During the procedure, the surgeon notices that the cystic cavities contain a "machinery oil"-like fluid. Which of the following is the most likely diagnosis?

64) A 5-year-old female child is brought to the emergency department due to fever, chills and abdominal pain. She has been complaining of burning micturition and abdominal pain for the last 2 days. Her temperature is 102 F (38.9C), respirations are 20/min, pulse is 130/min, and blood pressure is 90/60 mmHg. Physical examination reveals costovertebral angle tenderness. Urine analysis shows pyuria, significant bacteriuria, WBC casts, positive nitrite, and esterase. What is the most likely cause of this condition in children?

65) A 10-year-old girl is brought to the office for a follow-up visit. She has been previously diagnosed with vesicoureteral reflux, and has had multiple episodes of acute urinary tract infections in the past. Intravenous pyelography (performed on her last visit) reveals bilateral focal parenchymal scarring and blunted calyces. What is the most likely diagnosis?

66) A patient presents to the emergency center with a 6-hour history of fever to 38.9C (102F). Her mother reports that the patient appeared to be feeling poorly, that she had been eating less than normal, and that she vomited once. About 2 hours prior to arrival at the ER, the mother states that she noted a few purple spots scattered about the body on the patient, especially on the buttocks and legs. On the 30-minute ride to the ER, the purple areas spread rapidly and became coalesced in areas, and the patient is now obtunded. Which of the following is the most likely diagnosis?

67) A term neonate appears healthy at birth and receives routine perinatal care. Ten days after delivery, the infant develops severe eyelid edema with copious drainage of mucopurulent material and pseudomembrane formation. Which of the following is the most likely diagnosis?

68) A 4-year-old boy presents with severe pains in both of his legs. On physical examination, his temperature is 37.7 C (99.8 F), blood pressure is 108/68 mm Hg, pulse is 96/min, and respirations are 17/min. He is noted to have marked pallor on his lips and palpebral conjunctiva. Numerous purpura and petechiae are noted on his skin. His spleen is palpable 3 cm below his left costal margin. Laboratory evaluation reveals a white blood cell count of 1600/mm3; hemoglobin, 6.1 g/dL; and platelets, 36,000/mm3. Which of the following diagnoses is most consistent with these findings?

69) A 13-year-old healthy boy presents to the physician for a routine health maintenance visit. A urinalysis reveals 1+ proteinuria. There is no hematuria or bacteruria. His physical examination is unremarkable, revealing no edema and a normal blood pressure. Which of the following is the most likely diagnosis?

70) A previously healthy 18-month-old has been in a separate room from his family. The family notices the sudden onset of coughing, which resolves in a few minutes. Subsequently, the patient appears to be normal except for increased amounts of drooling and refusal to take foods orally. Which of the following is the most likely explanation for this toddler’s condition?

71) A 2-month-old infant is brought to the clinic for the evaluation of poor feeding. He was born at 32 weeks of gestation with a birth weight of 1200 g. The pertinent physical findings are pallor, tachypnea, tachycardia, and flow murmurs. The laboratory studies are as follows: Hb 7 g/dl, WBC 7,000/mm3, Platelets 230,000/mm3, Reticulocytes Low. The peripheral smear shows normocytic normochromic RBC. What is the most likely diagnosis?

72) A 5-year-old girl presents with a 3-day history of fever, dyspnea, and intermittent joint pain. She has a history of sore throat about 1 month ago. On physical examination, her temperature is 39.6 C (103.2 F), blood pressure is 94/60 mm Hg, pulse is 114/min, and respirations are 22/min. Her knees and elbow joints are swollen and tender to palpation. There is a grade III/VI diastolic murmur best heard at the apex. Multiple fine, pink macules are noted on her trunk. These macules are blanching in the middle. Which of the following is the most likely diagnosis?

73) An 8-year-old boy presents to the physician for a routine health maintenance visit. His mother states that he has had difficulty reading and concentrating in his second-grade class. On examination, seven café-au-lait spots on his body, as well as two small, soft masses above his orbit, are seen. He also has axillary freckling. His mother also has café-au-lait spots on her arms. Which of the following is the most likely diagnosis?

74) A one-year-old girl is brought to the emergency department (ED) by her mother due to a one-day history of fever and drowsiness. The child has been irritable since yesterday. On examination, she is hypothermic, lethargic and has nuchal rigidity. She flexes her hips when her neck is flexed. She appears septic, and large petechial and purpuric lesions are developing on her body. In the ED, she suddenly becomes hypotensive. Despite aggressive fluid and antibiotic resuscitation, the child dies. What will most likely be revealed as the cause of death during the autopsy of this child?

75) A 1 and half -year-old girl is sent to a children's hospital for evaluation following a nosebleed which was so severe as to require nasal packing and transfusion of platelet concentrates. When a blood sample had been drawn in the emergency room for serum chemistry studies, the local hospital laboratory had noted that the clot that formed was unusual in that it failed to retract. Peripheral blood smear obtained by finger puncture showed an appropriate number of normal-sized platelets, all of which were individual, without clumping. At the children's hospital, it was noted that the child's parents were cousins. Special platelet studies showed that the child's platelet's failed to aggregate with any physiologic aggregating agent, including a high concentration of exogenous ADP. Which of the following is the most likely diagnosis?

77) A 4-year-old boy and his family have recently visited a local amusement park. Several of the family members developed “gastroenteritis” with fever and diarrhea, but the 4-year-old’s stool was slightly different, as it contained blood. His mother reports that in the past 24 hours he developed pallor and lethargy; she relates that his face looks swollen and that he has been urinating very little. Laboratory evaluation reveals a hematocrit of 28% and a platelet count of 72,000/μL. He has blood and protein in the urine. Which of the following diagnoses is most likely to explain these symptoms?

78) A 4-day old pre term male neonate is being managed in the neonatal intensive care unit. He was born in the 34th week of gestation via lower segment caesarian section. On the first day of life, he developed tachypnea, grunting and nasal flaring. Chest x-rays showed a ground glass appearance of both lungs. He underwent endotracheal intubation and therapy with intravenous fluids, positive pressure ventilation, and intravenous antibiotics. He consequently showed remarkable improvement; however, he is currently beginning to have increased gastric residues. What is the most likely cause for this child's increased gastric residues?

79) A 14-month-old infant suddenly develops a fever of 40.2C (104.4F). Physical examination shows an alert, active infant who drinks milk eagerly. No physical abnormalities are noted. The WBC count is 22,000/μL with 78% polymorphonuclear leukocytes, 18% of which are band forms. Which of the following is the most likely diagnosis?

80) The parents of a 7-day-old infant bring her to your office for a swollen eye. Her temperature has been normal, but for the last 2 days she has had progressive erythema and swelling over the medial aspect of the right lower lid near the punctum. Her sclera and conjunctiva are clear. Gentle pressure extrudes a whitish material from the punctum. Which of the following ophthalmic conditions is the correct diagnosis?

81) A 14-year-old girl awakens with a mild sore throat, low-grade fever, and a diffuse maculopapular rash. During the next 24 hours, she develops tender swelling of her wrists and redness of her eyes. In addition, her physician notes mild tenderness and marked swelling of her posterior cervical and occipital lymph nodes. Four days after the onset of her illness, the rash has vanished. Which of the following is the most likely diagnosis?

82) A 5-day-old male term neonate has been passing maroon-colored stools for the past three days, along with frequent episodes of vomiting. He is being breastfed by his mother, who is an asthmatic. His vital signs are within normal limits. The physical examination is unremarkable. Stool examination is positive for RBCs and eosinophils. What is the most likely cause of this patient's findings?

83) A term neonate develops apnea, tachypnea, and seizures in the first 2 hours of life. The infant is large for gestational age and appears obese. Physical examination is otherwise unremarkable. Serum studies demonstrate a blood glucose level of 30 mg/dL. The mother most likely has which of the following conditions?

84) A 4-year-old child was brought in for evaluation of sleep problems. He cried and screamed within an hour of falling asleep. He seemed disoriented and confused; he did not seem aware of his parents’ presence. They were unable to arouse him to comfort him. This resolved spontaneously, and he had no recollection of the event the next morning. You informed the parents that he was most likely experiencing which of the following?

85) A male infant was found to be jaundiced 12 hours after birth. At 36 hours of age, his serum bilirubin was 18 mg/dL, hemoglobin concentration was 12.5 g/dL, and reticulocyte count 9%. Many nucleated RBCs and some spherocytes were seen in the peripheral blood smear. The differential diagnosis should include which of the following?

86) On a routine well-child examination, a 1-year-old boy is noted to be pale. He is in the 75th percentile for weight and the 25th percentile for length. Results of physical examination are otherwise normal. His hematocrit is 24%. The answer to which of the following questions is most likely to be helpful in making a diagnosis?

87) A 4-year-old boy is seen in the office for a general check-up. The child appears well nourished and has normal developmental milestones. His temperature is 36.6 C (98 F), pulse rate is 80/min, and blood pressure is 110/70 mmHg. On abdominal palpation, there is a lobular right-sided flank mass, and the kidneys are palpable bilaterally. What is the most likely cause of the flank mass in this child?

88) A 5-month-old boy is brought to the office for a mass in his left groin area. The infant is on the examination table, quietly sucking on his pacifier. On examination, there is a fluid-filled sac that does not reach the inguinal ring and transilluminates well. Which of the following is the most likely diagnosis?

89) A 6-month-old infant is taken to the emergency department because he had a seizure. Physical examination demonstrates premature closure of cranial sutures and markedly bowed legs. Laboratory studies demonstrate low serum phosphate levels, with normal vitamin D and parathyroid hormone levels. Urinalysis shows high phosphate levels, but no increased excretion of glucose, amino acids, or protein. The child's maternal grandfather had crippling bone disease, and his mother has mild bowing of the legs. Which of the following is most likely diagnosis?

92) A 3-year-old child is taken to a pediatrician because he develops burning pain, erythema, and swelling minutes after being exposed to the sun. Physical examination demonstrates erythema with swelling of the hands and arms. The skin is thickened on the backs of the hands but does not show blistering or scarring. Which of the following is the most likely diagnosis?

93) An infant born at 35 weeks’ gestation to a mother with no prenatal care is noted to be jittery and irritable, and is having difficulty feeding. You note coarse tremors on examination. The nurses report a high-pitched cry and note several episodes of diarrhea and emesis. You suspect which of the following?

94) A previously healthy full-term infant has several episodes of duskiness and apnea during the second day of life. Diagnostic considerations should include which of the following?

95) A very concerned mother brings a 2-year-old child to your office because of two episodes of a brief, shrill cry followed by a prolonged expiration and apnea. You have been following this child in your practice since birth and know the child to be a product of a normal pregnancy and delivery, to be growing and developing normally, and to have no chronic medical problems. The first episode occurred immediately after the mother refused to give the child some juice; the child became cyanotic, unconscious, and had generalized clonic jerks. A few moments later the child awakened and had no residual effects. The most recent episode (identical in nature) occurred at the grocery store when the child’s father refused to purchase a toy for her. Your physical examination reveals a delightful child without unexpected physical examination findings. Which of the following is the most likely diagnosis?

96) You are called to examine a 2-day old male infant due to difficulty in feeding. He becomes cyanotic and short of breath when he feeds, but turns pink when he cries. His prenatal, birth and family histories are unremarkable. His vital signs are normal. Chest auscultation is normal. His peripheral pulses are full and symmetric. What is the most likely diagnosis?

97) A neonate has an obviously abnormal foot. The foot is in a markedly plantar flexed position, with the sole facing the adjacent leg in a position of marked adduction. No other anomalies are noted on physical examination. Which of the following is the most likely diagnosis?

98) A mentally retarded 10-year-old boy presents with arthritis, nephrolithiasis, and progressive renal failure. Since his first years of life, he manifested peculiar neurologic abnormalities consisting of self-mutilative biting of the lips and fingers, choreoathetosis, and spasticity. Two male relatives on his mother's side presented with a similar condition and died in their teens. Which of the following is the most likely diagnosis?

99) A previously healthy 7-year-old girl comes to the office with complaints of episodic abdominal pain over the past several months. The pain is periumbilical and sharp but does not wake her from sleep or interfere with play. She has no fever, joint complaints, or constipation or diarrhea. Growth and development have been normal. The physical examination is within normal limits. Which of the following is the most likely diagnosis?

100) A 4-month-old male infant is brought to the office by his parents due to progressive lethargy, poor feeding, fatigue and increasing pallor for the past four weeks. His antenatal and birth histories are unremarkable. His diet consists mainly of breast milk. His immunizations are up-to-date. His mother's blood type is 0 +. Physical examination reveals a webbed neck, cleft lip, shielded chest, triphalangeal thumbs, and pale mucous membranes and conjunctivae. Cardiac auscultation reveals mild tachycardia and a systolic ejection murmur over the left upper sternal border. The initial investigations reveal the following: Hb 8 g/dl, Ht 26%, WBCs 7,000/mm3, Platelets 300,000 /mm3, Reticulocytes 04%, MCV 104 fl, Blood type A -, Bilirubin direct 0.1 mg/dl, Bilirubin total 1.0 mg/dl. What is the most likely diagnosis?

102) You are called to examine a one-day-old male neonate who gradually developed cyanosis over the past few hours. The infant was delivered vaginally at full term, assisted with forceps, and weighed 9 lbs. The Apgar scores were 7 and 8 at 1 and 5 minutes, respectively. Oxygen administration by mask does not relieve the cyanosis. Further examination reveals tachypnea, subcostal retractions, a normal S 1, single and loud S2, and no murmur. Which of the following is the most probable cause of the infant's cyanosis?

103) A 29-year-old woman presents to the delivery room in labor at 35 weeks' gestation with a temperature of 40 C (104 F). She lives on a dairy farm and is in the habit of drinking unpasteurized milk from her cows before sending it to the dairy. For the past 3 days she has been unable to attend to her chores because of fever, headache, mild diarrhea, and a general feeling of illness. When her amniotic membranes rupture, the fluid is dark, cloudy, and brownish-green. At birth, the infant has no malformations or edema, but is in severe respiratory distress. Which of the following is the most likely diagnosis?

104) A previously healthy 13-year-old girl presents to the emergency department with an acute onset of red urine after she played soccer in the morning. Her physical examination is unremarkable. Urinalysis shows a red color; pH, 6.2; specific gravity, 1.024; glucose, negative; blood, +4; protein, trace; nitrite, negative; leukocyte esterase, negative; white blood cell, 0/hpf; red blood cell, 1/hpf. Which of the following is the most likely explanation of the red urine?

105) A 1-month-old infant is seen in a well-baby clinic. The mother states that the baby is constipated and feeds poorly. On examination, he is jaundiced, has a large posterior fontanel and an umbilical hernia, and exhibits poor muscle tone. He has gained only 300 g since discharge from the normal newborn nursery. Which of the following is the most likely diagnosis?

106) A 15-year-old girl has a round, 1-cm cystic mass in the midline of her neck, at the level of the hyoid bone. The mass is deep to the skin and moves slightly when the patient swallows. When the mass is palpated at the same time that the tongue is pulled, there seems to be a connection between the two. The mass has been present for at least 10 years, but only recently bothered the patient because it became infected. Which of the following is the most likely diagnosis?

108) A 4-month-old infant is evaluated by a dermatologist because of thick, erythematous skin with fine scaling, principally involving his face. The mother reports that the infant is "always scratching his face." An older brother and a maternal uncle had a similar condition. Screening hematologic studies show the following: Erythrocyte count 5.1 million/mm3, Leukocyte count 12,000/mm3, Segmented neutrophils 80%, Bands 5%, Eosinophils 3%, Basophils 1%, Lymphocytes 5%, Monocytes 6%, Platelet count 35,000/mm3 , with the comment that the platelets are smaller than normal. Serum immunoglobulin studies demonstrate the following: IgA 120 mg/dL, IgE 2300 IU/mL, IgG 900 mg/dL, IgM 15 mg/dL. Patients with this condition have a significantly increased incidence of which of the following?

109) A 15-year-old athlete is in your office for his annual physical examination before the start of football season. He has no complaints, has suffered no injuries, and appears to be physically fit. On his heart examination, you note a heart rate of 100 beats per minute, and a diffuse point of maximal impulse (PMI) with a prominent ventricular lift. He has a normal S1 and S2, with an S4 gallop. He has no murmur sitting, but when he stands you clearly hear a systolic ejection murmur along the lower left sternal edge and the apex. For which of the following conditions is this examination most consistent?

110) A 10-year-old Caucasian boy is brought to the emergency room by his mother with right hemiplegia of sudden onset. The mother says that the child fell on a pencil in his mouth, ten hours before the onset of symptoms. His past medical history is insignificant. Family history is not significant. His blood pressure 110/60 mmHg and heart rate is 90/min. Physical examination reveals dense right hemiplegia, right hemianesthesia, and mild motor aphasia. Cardiac auscultation reveals S3. What is the most probable cause of this patient's condition?

111) A school teacher calls you to report that his 7-year-old student had about 10 episodes of eye blinking and gabbling today, which lasted approximately 30 seconds each. The child sat in his chair and did not have any postictal confusion. The teacher noticed several similar episodes during the last month, as well as a decline in the child's school performance. What type of seizure does this child have?

112) A 10-year-old girl has had a “cold” for 14 days. In the 2 days prior to the visit to your office, she has developed a fever of 39°C (102.2°F), purulent nasal discharge, facial pain, and a daytime cough. Examination of the nose after topical decongestants shows pus in the middle meatus. Which of the following is the most likely diagnosis?

113) A 7 -year-old girl is brought to the physician's office by her mother due to recurrent, prolonged episodes of nausea and severe vomiting for the past 4 days. According to the mother, the vomiting starts in the early morning and recur 7 to 8 times daily. The child denies any headache, abdominal pain, diarrhea, chest pain or respiratory distress. She has had two similar episodes of vomiting and nausea in the past year, which resolved spontaneously. The mother has a history of migraines. On examination, the child is afebrile and has pallor with signs of mild dehydration. The abdomen is soft and non-tender to palpation. What is the most likely cause of this child's symptoms?

114) A 14-year-old boy has pain in his left leg. An x-ray shows a tumor and a biopsy reveals histopathologic features characteristic of neural origin. Which of the following is the most likely diagnosis?

115) A 7-year-old boy arrives at the emergency room in acute distress. Over the past 3 to 4 days he has become progressively ill with generalized fatigue and mild, mid-abdominal pain that have become steadily worse. On physical examination he has a maculopapular rash on his thighs and feet with some spread of the rash to his buttocks. The rash does not blanch and the some lesions near the ankles look petechial or bruised. His temperature is 39.0 C (102.2 F) and he is drawing his knees to his chest for relief of his stomach pains. He is nauseated and vomited once before coming to the hospital. He has semi-soft dark stool, which is guaiac-positive. The boy has not voided since early morning and cannot provide a urine sample. The doctor determines that he is 10% dehydrated and asks the nurse to start intravenous fluids. Which of the following is the most likely diagnosis?

116) A newborn male has oliguria and a midline mass in the lower abdomen. What is the most likely diagnosis?

117) A 22-month-old boy who recently immigrated from Eastern Europe with his family is brought to your office by his mother who is worried that he seems to tire easily. She describes how he becomes short of breath with even mild physical activity and cannot keep up with his peers during play. The boy is at the 40th percentile for height and 20th percentile for weight. On general examination, there is no clubbing, cyanosis, or peripheral edema, but there is a harsh 3/6 holosystolic murmur over the left lower sternal border and a rumbling diastolic murmur over the cardiac apex. Which of the following is the most likely cause of his symptoms?

118) A 5-month-old child was normal at birth, but the family reports that the child does not seem to look at them any longer. They also report the child seems to “startle” more easily than he had before. Testing of his white blood cells (WBCs) identifies the absence of β-hexosaminidase A activity, confirming the diagnosis of which of the following?

119) The family of a 4-year-old boy has just moved into your area. The child was recently brought to the emergency department (ED) for an evaluation of abdominal pain. Although appendicitis was ruled out in the ED and the child’s abdominal pain has resolved, the ED physician requested that the family follow up in your office to evaluate an incidental finding of an elevated creatine kinase. The family notes that he was a late walker (began walking independently at about 18 months of age), that he is more clumsy than their daughter was at the same age (especially when trying to hold onto small objects), and that he seems to be somewhat sluggish when he runs, climbs stairs, rises from the ground after he sits, and rides his tricycle. A thorough history and physical examination are likely to reveal which of the following?

120) A 15-month-old boy is brought into the clinic with a 1-day history of fever, decreased oral intake, and runny nose. His vital signs are within normal limits except for a temperature of 39.5 C (103.1 F). He is active and in no distress. His ears are clear bilaterally. There is a clear nasal discharge. Multiple small (1-2 mm) vesicular lesions are noted on the mucosa of the anterior tonsillar pillars and posterior palate. The rest of his examination is within normal limits. Which of the following is the most likely diagnosis?

121) A 6-month-old infant presents to the emergency department with the new onset of weak cry, decreased activity, and poor feeding. The mother also states that the infant has been constipated for the past 2 days. On physical examination, the infant has a very weak cry, poor muscle tone, and absent deep tendon reflexes. Which of the following is the most likely diagnosis?

122) You are called to examine a 2-day-old male, newborn after he was noted to be cyanotic. He was born at term. His antenatal and birth histories are unremarkable. Auscultation reveals a holosystolic murmur at the left, lower sternal border and a single S2. No rales or rhonchi are heard. Chest radiograph reveals decreased pulmonary vascular markings and a normal-sized heart. EKG reveals left axis deviation. What is the most likely diagnosis?

123) A 2-year-old boy has been vomiting intermittently for 3 weeks and has been irritable, listless, and anorectic. His use of language has regressed to speaking single words. In your evaluation of this patient, which of the following is the most reasonable diagnosis to consider?

124) A 15-year-old boy is seen in the pediatrician's office for a health maintenance physical examination. The boy reports a heavy, dragging sensation in his left scrotum. The sensation is more pronounced after exercise. He denies any scrotal pain. He is not sexually active. Examination of his genitalia indicates Tanner stage 4. There is a palpable fullness over his left scrotum. Both testes are normal in size and smooth in contour. Which of the following is the most likely explanation of these findings?

125) A 5-year-old child undergoes a school entrance physical examination. The pediatrician notices grey-brown pigmentation on the skin of his forehead, hands, and pretibial regions. Subconjunctival areas near the corneoscleral junction show wedge-shaped, yellow-brown discoloration (pingueculae). Enlargement of both the spleen and the liver are noted on abdominal examination. Needle biopsy of the spleen demonstrates the presence of unusually large (20- to 100-mm diameter) reticuloendothelial histiocytes with a "crumpled-silk" appearance. Bone marrow biopsy demonstrates the presence of the same type of cells. Which of the following is the most likely diagnosis?

126) A term male infant is found to be cyanotic shortly after birth and requires endotracheal intubation. On physical examination, his blood pressure is 68/34 mm Hg (equal in all four extremities), pulse is 180/min, and respirations are 32/min. His precordium is dynamic, has a grade III systolic murmur, and a single S2. Chest radiography shows a normal heart size and increased pulmonary vascular markings. An arterial blood gas on an FiO2 of 100% shows pH 7.34; PaCO2: 47 mm Hg; PaO2: 46 mm Hg. Which of the following diagnoses is most consistent with these findings?

127) A 6-month-old boy is found to have bilateral metaphyseal fractures of both proximal and distal ends of the tibia. The mother says that her boyfriend takes care of the infant while she is at work. Her boyfriend explains the injuries as the result of multiple falls from bed. Which of the following is the most likely diagnosis?

129) A 2-year-old child has had red, weeping, crusted lesions of the face, scalp, diaper area, and extremities since about age 2 months, with multiple periods of exacerbation and improvement. Attempts to remove potentially irritating substances have not modified the course of the rashes. The child is noted to be constantly scratching and rubbing involved areas. There is a strong family history of hay fever and asthma. Which of the following is the most likely diagnosis?

130) A 7-year-old Caucasian boy is brought to the clinic because of poor performance in school. His mother says that his teachers have been complaining about his poor attention in the classroom for the past 8 months. They have also complained that he is out of his seat often, fidgets, and talks excessively, gets distracted easily, and interrupts class and other students. His mother has noticed that he often loses his things, and she is having more and more difficulty disciplining him at home. His antenatal and postnatal history is insignificant. His parents never had any similar problems with his 10-year-old sister. What is your clinical diagnosis?

132) A 17-year-old girl presents with a 4-week history of intermittent fever, increasing fatigue, generalized myalgia, and swelling of both her knees and ankles. There is a fine erythematous rash on her back, and she has swollen knees and ankles; the remainder of her physical examination is unremarkable. Initial laboratory evaluation shows: Leukocytes 11,400 cells/mm3, Hemoglobin 8.8 g/dL, Blood urea nitrogen 4 mg/dL, Creatinine 1.4 mg/dL, Glucose 98 mg/dL, C3 complement 36 mg/dL (normal >80 mg/dL), Antinuclear antibody titer 1:3200, Anti-double-stranded DNA titer 1:640, Antineutrophil cytoplasmic antibodies: Negative, Urinalysis Moderate hematuria (50 RBC/hpf), Moderate proteinuria (400 mg/dL). Which of the following is the most likely diagnosis?

133) A vomiting infant is brought to the emergency room. The blood work results reveal a normal blood count, but a hyponatremic, hypochloremic, metabolic alkalosis. Which of the following would be consistent with these findings?

135) A 12-year-old male is brought to your office by his mother because of a several month history of back pain. He also experienced bed wetting recently. His past medical history is insignificant. He tried acetaminophen for pain relief. He does not smoke or consume alcohol. His temperature is 36.7 C (98 F), blood pressure is 110/65 mmHg, pulse is 80/min, and respirations are 16/min. Physical examination reveals a palpable "step off" at the lumbosacral area. Straight-leg raising test is negative on both sides. Perianal sensation tested by pinprick test is decreased, but anal reflex is normal. What is the most probable diagnosis in this patient?

136) A 16-month-old is taken to the emergency room after falling while learning to walk. The toddler has an enlarging, swollen bruise on his forehead, which is now over two inches across. The parents say that the bruise is noticeably larger than it was when they entered the emergency room an hour earlier. A blood sample is drawn, and the child oozes blood at the puncture site for 25 minutes. Clotting studies on the blood sample show a prolonged PTT and a normal PT. Follow-up studies show very low levels of factor VIII. Which of the following is the most likely diagnosis?

137) A previously healthy 8-year-old boy has a 3-week history of low-grade fever of unknown source, fatigue, weight loss, myalgia, and headaches. On repeated examinations during this time, he is found to have developed a heart murmur, petechiae, and mild splenomegaly. Which of the following is the most likely diagnosis?

138) A 10-year-old boy is brought by his parents to the emergency department for the evaluation of headaches, fever, chills, and a rash over his neck, chest, and axillae. The rash appeared today, and for the past two days the child was complaining of a sore throat. He has no history of allergies, and his immunizations are up-to-date. His blood pressure is 112/70 mmHg, pulse is 1 08/min, respirations are 20/min, and temperature is 38.3C (101 F). Examination reveals an erythematous rash with a sandpaper-like texture, and which blanches with pressure. There is submandibular tender lymphadenopathy, and the throat is erythematous with gray-white exudates. What is the most likely diagnosis?

139) A 2-year-old boy is referred to your office for the evaluation of a white eye reflex. His mother suspects a hearing problem because he does not respond when she calls out his name. The physical examination reveals a continuous, machinery murmur over the right 2nd intercostal space and purple lesions on his arms and chest. The initial investigations reveal thrombocytopenia. What is the most likely diagnosis?

140) You find a discrete, whitish polyp that extends through the tympanic membrane in a child with a history of recurrent otitis media. This most likely represents which of the following?

141) A 5-day-old male premature infant in the NICU develops a decreased level of consciousness, hypotonia and decreased spontaneous movements. He was delivered vaginally at 32 weeks of gestation, and his birth weight was 1800g. Examination reveals a lethargic infant with a weak and high-pitched cry, prominent scalp veins, tense fontanels, and eyes directed downward, poor suckling, hypotonia. CT scan reveals dilation of the entire ventricular system, with distinct enlargement of the subarachnoid space over the cerebral cortex. What is the most likely cause of the patient's condition?

142) A 12-month-old infant presents with bilious vomiting and abdominal distention for 10 hours. His mother states that the infant has been constipated since birth and failed to pass meconium during the first 48 hours of life. On examination, he is very irritable. His length and weight are both below the 5th percentile according to his age. His abdomen is moderately distended. After a digital rectal examination, a fair amount of stool ejects out from the anus. Which of the following is the most likely diagnosis?

143) A 9-year-old boy is brought to the pediatrician's office for bed-wetting. His mother states that he has never been dry at night. Occasionally, he has problems controlling his bladder during the day. On physical examination, his blood pressure is 98/56 mm Hg. Both his weight and height are below the 5th percentile for his age. His bladder is enlarged and palpable above the symphysis pubis. Which of the following is the most likely cause of his problem?

144) A 4-day-old female infant presents to the emergency department with vomiting and abdominal distention. The mother states that the vomitus was green. The infant also has had difficulty feeding and has been hard to console. The mother had an uncomplicated pregnancy. The infant passed meconium within 12 hours after birth. She also had several small, seedy, yellowish stools each day since birth. On physical examination, she is very irritable, her anterior fontanelle is slightly depressed. Her abdomen is distended. Which of the following is the most likely diagnosis?

145) A previously healthy 11-year old boy presents to the physician with a fever and persistent vomiting for 4-5 days. Initially, the emesis was clear, but now it contains streaks of bright red blood. Findings on a physical examination, complete blood count, and serum electrolytes are within normal limits. Which of the following is the most likely cause of the hematemesis?

146) A 7 -year-old boy is brought to the emergency department after falling on his outstretched hand. On examination, there is minimal swelling at the right elbow. The skin on the right forearm appears tense, and severe pain is present. The brachial pulses are good bilaterally, and sensations are intact in both upper limbs. X-rays of the right upper limb show a displaced anterior fat pad. Which of the following statements is true about this condition?

147) A 3-month-old infant has a history of chronic constipation. A fulminant watery diarrhea develops over a period of 2 days, and the infant is taken to the emergency department in an obviously severely dehydrated state. Plain x-ray films of the abdomen demonstrate a massively dilated transverse colon. Which of the following is the most likely diagnosis?

148) A mother brings her 9-month-old daughter to the pediatrician with complaints of a rash. The mother states that the infant had a high fever [temperature up to 40.0 C (104 F)] for 3 days prior to developing the rash, but is now afebrile. The mother also says that the infant has had a runny nose and a slight cough for the past 3 days. On examination, there is a fine macular rash on the infant's trunk and neck. The examination is otherwise within normal limits, and the infant is playful and smiling. Which of the following is the most likely diagnosis?

149) A 20-month-old presents to the office with a 2-day history of a harsh, barking cough. His mother states that the cough sounds like a seal. She also states he has not had any fever, although he had a runny nose earlier in the week. On examination, he is notably hoarse with inspiratory stridor. He is not drooling and is sitting on his mother's lap comfortably. The rest of his examination is within normal limits. Which of the following is the most likely diagnosis?

150) A 4-year-old girl is brought to the physician by her mother who is concerned because her child has a vaginal discharge. Starting 2 days ago, the child began scratching her vulva and complaining of burning with urination. The child is otherwise healthy and has never had a similar problem. Examination reveals normal structural anatomy for a 4-year-old girl. There is no evidence of atrophy. There is an inflammatory erythema on the medial aspects of the labia majora and excoriations. There is a mucous discharge with a few flecks of blood intermixed. Which of the following is the most likely cause of a vaginal discharge in this patient?

151) A 1-year-old child presents with failure to thrive, frequent large voids of dilute urine, excessive thirst, and three episodes of dehydration not associated with vomiting or diarrhea. Over the years, other family members reportedly have had similar histories. Which of the following is the most likely diagnosis?

152) A 6-month-old infant has poor weight gain, vomiting, episodic fevers, and chronic constipation. Laboratory studies reveal a urinalysis with a pH of 8.0, specific gravity of 1.010, 1+ glucose, and 1+ protein. Urine anion gap is normal. Serum chemistries show a normal glucose and a normal albumin with a hyperchloremic metabolic acidosis. Serum phosphorus and calcium are low. What is the best diagnosis to explain these findings?

153) A 2-year-old girl is taken to a pediatrician because she has developed a rash and seems unusually unsteady when she tries to walk. Physical examination demonstrates a diffuse rash on body parts exposed to sun. Also noted are short stature, possible mental retardation, and ataxia. Screening studies demonstrate increased total amino acids in the urine. Which of the following is the most likely diagnosis?

155) A 10-year-old boy, the star pitcher for the Salt Lake City Little League baseball team, had a sore throat about 2 weeks ago but did not tell anyone because he was afraid he would miss the play-offs. Since several children have been diagnosed with rheumatic fever in the area, his mother is worried that he may be at risk as well. You tell her that several criteria must be met to make the diagnosis but the most common finding is which of the following?

156) A 6-year-old female is brought to the physician with a rash and joint pains. Her mother reports that she has been previously healthy except for a sore throat a few weeks ago. One week ago, the patient developed pain in her knees. The knee pain resolved after a few days, but now her ankles and wrists are tender. She has also developed a pink rash on her trunk that is non-pruritic. Vital signs are temperature 38.3 c (101 F), pulse 85/min, and respiratory rate 20/min. On examination, there is pain and stiffness during manipulation of the wrists and ankles. A faint, erythematous, centrifugal rash on her trunk and proximal limbs is present. Laboratory studies show: Complete blood count: Hemoglobin 12.5 g/dL, MCHC 32%, MCV 85 fl, Reticulocyte count 0.1%, Platelet count 200,000/mm3, Leukocyte count 6,500/mm3, Neutrophils 56%, Eosinophils 1%, Lymphocytes 33%, Monocytes 10%, C-reactive protein 3.5 mg/dL, Erythrocyte sedimentation rate 38 mm/hr. Which of the following is the most likely diagnosis?

157) A previously healthy 18-month-old male comes to the physician for evaluation of fever. His mother reports that he has had a fever ranging from 1 02.2 F (39.0 c) to 104.0 F (40.0 C) for the past five days. He has also become increasingly irritable with decreased appetite. His mother reports that he does continue to take some liquids. There are no known sick contacts. On examination, the infant's temperature is 102.5 F (39.2 C), pulse is 120/min, and respiratory rate is 20/min. He is irritable during the examination. There is conjunctival erythema bilaterally, with serous drainage from both eyes. His oropharynx is erythematous and his lips are fissured. There is a 2 cm anterior cervical lymph node palpable on the right side. His neck is otherwise supple and he is able to flex his chin to his chest without difficulty. There is mild abdominal tenderness to palpation. His hands and feet are slightly erythematous and edematous and there is a maculopapular rash on the trunk. Which of the following is the most likely diagnosis?

158) A 2-week-old infant is brought to the office for a newborn visit. His mother states that the he has been a very slow eater and that he is constipated, not having had a bowel movement in 3 days. On physical examination, the infant has poor muscle tone, an enlarged tongue, an umbilical hernia, an enlarged anterior fontanelle, and hypothermia. He also looks slightly jaundiced, with slightly dry skin and brittle hair. Which of the following is the most likely diagnosis?

159) A 12-year-old child is brought to his pediatrician for a routine health maintenance visit. He has been well except for occasional attacks of asthma and has met all development milestones. His immunizations are up to date. He occasionally uses theophylline for his asthma. Physical examination is remarkable for a blood pressure of 150/90 mm Hg in both arms. Which of the following is the most likely cause of his hypertension?

160) A 5-year-old boy is brought to the emergency department due to general malaise and a swollen scrotum. His mother noticed the swollen scrotum today, and is sure that "it was not there yesterday." He had a low-grade fever and a cough two weeks ago, and "hasn't been himself ever since." He has no significant past medical history. On examination, he looks ill and lethargic. He has palpable purpura on his buttocks and lower legs. He has a swollen right scrotum which is slightly tender to palpation, and his abdomen is moderately tender to palpation. Urinalysis reveals the presence of a small amount of blood and protein. He is subsequently admitted for observation. Which of the following adverse outcomes is he most likely to develop?

161) A mentally retarded 14-year-old boy has a long face, large ears, micropenis, and large testes. Chromosome analysis is likely to demonstrate which of the following?

162) A 5-month-old child with poor growth presents to the ER with generalized tonic-clonic seizure activity of about 30-minute duration that stops upon the administration of lorazepam. Which of the following historical bits of information gathered from the mother is most likely to lead to the correct diagnosis in this patient?

163) A 13-year-old girl presents with parental concerns of poor posture. She has not had any back pain. On examination, she has unequal shoulder height, asymmetric flank creases, and a forward-bending test that shows rib asymmetry. The physical examination is otherwise normal. Which of the following is the most likely cause of her condition?

164) An 18-month-old boy presents with a history of fever to 39.0°C for 5 days. He has also been irritable and has not been drinking well. Associated symptoms include red eyes, a rash, and some trouble walking. On physical examination, he has a temperature of 39.5°C. He has bilateral bulbar conjunctivitis, a strawberry tongue, an inflamed oral pharynx, edema of the hands and feet, a morbilliform rash, and cervical lymphadenopathy. He is very irritable. His CBC shows a WBC of 15,000/mm3 with 60% neutrophils, 35% lymphocytes, and 5% monocytes. His hemoglobin is 12.0 g/dL and platelet count is 500,000/ mm3. Which of the following is the most likely diagnosis?

165) An infant is delivered at full term by a spontaneous vaginal delivery to a 29-year-old primigravida. At delivery, the infant is noted to have subcostal retractions and cyanosis despite good respiratory effort. The abdomen is scaphoid. On bag and mask ventilation, auscultation of the lungs reveals decreased breath sounds on the left, with heart sounds louder on the right. Which of the following is the most likely diagnosis?

166) A 12-month-old girl has been spitting up her meals since 1 month of age. Her growth is at the 95th percentile, and she is otherwise asymptomatic and without findings on physical examination. Which of the following is the most likely diagnosis?

167) A 14-year-old girl has a 9-month history of diarrhea, abdominal pain (usually periumbilical and postprandial), fever, and weight loss. She has had several episodes of blood in her stools. Which of the following is the most likely diagnosis?

168) A 12-year-old girl complains of intermittent palpitations. She had previously been in excellent health and has met all development milestones. There is no family history of heart disease. She is on no medications and takes no drugs. She states that the palpitations begin and end suddenly and usually last a couple of hours. She is otherwise asymptomatic between episodes. The physical examination is normal. An ECG reveals a shortened PR interval and a slow upstroke of the QRS wave in lead III. Which of the following is the most likely diagnosis?

169) An 11-year-old boy is brought to the office by his mother because "he is sick." He has had headaches for the past several weeks, and has vomited 4 times in the past 5 days. He drinks large amounts of water and goes to the bathroom all the time. He is no longer interested in playing football and going out with his friends. His temperature is 37.0C (98.6F), blood pressure is 118/78 mm Hg, pulse rate is 84/min, and respirations are 16/min. On examination, there is loss of peripheral visual fields. His laboratory findings are as follows: W BC 7,800/mm3, Hemoglobin 12.6 g/dl, Hematocrit 35%, Platelets 199,000/mm3, Sodium 145 mEq/L, Potassium 3.6 mEq/L, Bicarbonate 24 mEq/L, Blood urea nitrogen 18 mg/dl, Serum creatinine 1.0 mg/dl, Blood glucose 88 mg/dl. X-rays of the head reveal a calcified lesion above the sella. What is the most likely diagnosis?

170) A full-term neonate presents with hypotonia, lethargy and poor feeding over the past three hours. The pregnancy was uneventful, but during delivery, the neonate presented with shoulder dystocia and subsequently obtained a fracture of the clavicle. His Apgar scores are 7 and 8 at one and five minutes, respectively. His birth weight is 4000g. His vital signs are normal. Physical examination reveals an enlarged tongue, mild microcephaly, prominent occiput, prominent eyes and omphalocele. Abdominal palpation reveals an enlarged liver and kidneys. The initial work-up reveals hypoglycemia and hyperinsulinemia. What is the most likely diagnosis?

171) Your older sister, her husband, their 2-day-old infant, and their pet Chihuahua arrive at your door. The parents of the child are concerned because the pediatrician noted the child was “yellow” and ordered some studies. They produce a wad of papers for you to review. Both the mother and baby have O-positive blood. The baby’s direct serum bilirubin is 0.2 mg/dL, with a total serum bilirubin of 11.8 mg/dL. Urine bilirubin is positive. The infant’s white blood cell count is 13,000/μL with a differential of 50% polymorphonuclear cells, 45% lymphocytes, and 5% monocytes. The hemoglobin is 17 g/dL, and the platelet count is 278,000/μL. Reticulocyte count is 1.5%. The peripheral smear does not show fragments or abnormal cell shapes. Which of the following is the most likely explanation for this infant’s

172) A 14-day-old male infant is brought to the emergency department due to spasms involving the whole body. He has been having very poor suckling over the last couple of days. He was delivered vaginally by an untrained birth attendant, and his mother never sought any pre- or antenatal care. The pertinent physical finding is a swollen and erythematous umbilical cord. What is the most likely diagnosis of this patient?

175) A 14-year-old African-American boy presents to your office with difficulty walking for the past several weeks. He complains of pain in the right hip. He describes two episodes of severe hip pain and one previous episode of abdominal pain requiring hospitalization. Physical examination reveals motion restriction in the right hip joint. His joint is not erythematous or tender to palpation. His hematocrit is 22%. This patient's difficulty walking is most likely secondary to which of the following?

176) A 2-year-old girl is brought to her pediatrician by her parents because of increasing lethargy and irritability. She has just started walking, and is teething and likes to chew on the woodwork around the windows. Physicalexamination reveals a tender abdomen. Laboratory studies indicate high iron and ferritin levels. The peripheral blood smear shows basophilic stippling. Which of the following is the most likely diagnosis?

177) A 10-hour-old newborn is noted to have a swelling in the scalp which was not present at birth. The swelling is limited to the surface of one cranial bone. There are no visible pulsations, indentations of the skull, or discoloration of the overlying scalp. What is the most likely diagnosis?

178) A 4-year-old boy is brought to the office because his school teacher thinks that his dusky blue appearance may have something to do with his inability to participate in regular school activities. His mother says that he has always appeared slightly out of breath. He has no history of any trauma, past surgery or medical conditions. His birth history is unremarkable. Physical examination reveals perioral cyanosis and a systolic murmur along the left sternal border. When the child squats, the murmur disappears and the cyanosis slightly improves. What is the most likely diagnosis of this patient?

179) A 2-month-old infant is evaluated by a pediatric cardiologist. The infant was noted at birth to have an upper left sternal border ejection murmur. The infant at that time was not cyanotic, but slowly developed cyanosis over the next two months. At the time of the pediatric cardiologist's examination, an ECG showed right axis deviation and right ventricular hypertrophy. A chest x-ray film showed a small heart with a concave main pulmonary artery segment and diminished pulmonary blood flow. Which of the following is the most likely diagnosis?

180) A 6-year-old boy is brought to the emergency department because of the acute onset of headache, nausea, and vomiting. On arrival, physical examination reveals marked nuchal rigidity and funduscopic evidence of papilledema. A head CT scan reveals a solid tumor in the posterior fossa, centered in the cerebellar vermis and extending to the fourth ventricle. An emergency craniotomy is performed, during which a small sample of the tumor is sent to the pathologist for a frozen section consultation. Which of the following is the most likely diagnosis?

181) A 15-month-old girl is brought to the office by her mother due to failure to thrive. For the past three months, the child has had foul-smelling, non-bloody, loose stools 7 to 8 times daily. On examination, she is irritable and has a protruding belly and trace pre-tibial edema. There are erythematous vesicles symmetrically distributed over the extensor surfaces of her elbows and knees. Preliminary laboratory investigations are significant for hypochromic microcytic anemia, and stool examination is negative for ova or parasites. What is the most likely cause of failure to thrive in this child?

184) A 25-year-old woman brings her 5-day-old infant to the emergency room after noticing that he bruises very easily. Her pregnancy was normal, and the baby was born at term via vaginal delivery at home. This is the child's first visit to the doctor. He is exclusively breast-fed, and there is no family history of bleeding disorders. On physical examination, his vital signs are within normal limits. You note several ecchymotic skin lesions, but his exam is otherwise normal. Laboratory studies show the following: Prothrombin time 20 sec, Partial thromboplastin time 37 sec, Platelets 200,000/mm3. Which of the following is the most likely cause of his current condition?

185) A 7-year-old girl is brought to the physician because of an exanthematous rash associated with malaise and headache for 2 days. On examination, the child shows a fiery red facial rash with a characteristic "slapped cheek" pattern and pallor around the mouth. There is no fever. In immunocompromised patients, the pathogen that causes this condition may result in which of the following manifestations?

186) A 12-year-old boy is brought to the physician because of pain in his right leg for the past 3 weeks. The pain frequently occurs at night and is localized to the tibia, a few centimeters below the knee. The mother reports that the pain is promptly relieved by aspirin and that the child has had no fever. Examination reveals no tissue swelling or redness about the site of pain. X-ray films show a 1-cm radiolucent focus in the tibial cortex surrounded by marked bone sclerosis. Which of the following is the most likely diagnosis?

187) A 7-year-old boy is brought to the physician because of recurrent headaches. The child feels nauseated before and during each attack, and derives some relief from lying down in a dark room. Noises, bright light, and fatigue seem to trigger the episodes. The child frequently complains of headaches at school, and his mother has been occasionally compelled to take him home. The mother is worried about the possibility of a serious illness. She reports that the child's father has similar headaches. The child's growth is normal, and a neurologic examination fails to reveal any abnormality. Which of the following is the most likely diagnosis?

188) A 12-year boy is brought to the emergency room by his parents after a several day history of progressive weakness. He has been a healthy child who has met all development milestones and all his immunizations are up to date. He reports that he had an upper respiratory infection 2 weeks ago. On physical examination, his vital signs are labile with a pulse range of 60-100/ min and systolic blood pressure ranging from 80-120 mm Hg. He is alert and oriented. Neurologic examination is impressive for bilateral weakness in the upper and lower extremities. Deep tendon reflexes are absent and sensation is intact. Which of the following is the most likely diagnosis?

189) A 2-year-old boy is brought to the office due to recurrent skin and soft tissue infections. When he was 2- months-old, he had a perianal furuncle that was incised and drained because it was unresponsive to oral antibiotics. At 7 months of age, he had a left inguinal Klebsiella pneumoniae lymphadenitis. His other past infections include a left calf cellulitis that grew Serratia marcescens and a left inguinal abscess that grew Staphylococcus epidermidis. On examination, he has hepatosplenomegaly, and enlarged axillary and inguinal lymph nodes. The screening tests for humoral, cell-mediated, and complement-mediated immunity are normal. The nitroblue tetra zolium (NBT) slide test is abnormal. What is the most likely diagnosis?

190) A fetus is delivered at 40 weeks' gestation. During labor, the fetal heart monitor shows late decelerations and loss of short- and long-term variability. The membranes are ruptured to expedite the delivery. The fluid is noted to contain meconium. The infant is delivered 45 minutes later. At delivery, the infant appears to be cyanotic and limp. He has poor tone and deep reflexes. Moro's reflex is absent. Ten hours later, he experiences a seizure. Which of the following best explains this infant's perinatal course?

191) A neonate is very small for gestational age, shows hypotonia, marked skeletal muscle, and subcutaneous fat hypoplasia. During delivery, a large volume of amniotic fluid was released at rupture of membranes. The placenta was small, and only a single umbilical artery was noted. The face has a pinched appearance with hypoplastic orbital ridges, short palpebral fissures, and a small mouth and jaw. The head is small with prominence of the occiput. The ears are low set and malformed. The infant's fists are clenched, with overlapping of the third and fourth fingers. The feet are clubbed, and the great toe is shortened. Which of the following is most likely diagnosis?

193) A 17-year-old boy is brought to the emergency department by his parents with the complaint of coughing up blood. He is stabilized, and his hemoglobin and hematocrit levels are 11 mg/dL and 33%, respectively. During his hospitalization, he is noted to have systolic blood pressure persistently greater than 130 mm Hg and diastolic blood pressure greater than 90 mm Hg. His urinalysis is remarkable for hematuria and proteinuria. You are suspicious the patient has which of the following?

194) A 4-year-old boy is being evaluated for short stature. He has a history of multiple bone fractures in the past. He requires a wheelchair to ambulate and has hearing difficulty. On physical examination, his height is below the 5th percentile. His sclerae are blue in color. There is marked deformity of his lower extremities. Which of the following is the most likely diagnosis?

195) The mother of a 2-week-old infant reports that since birth, her infant sleeps most of the day; she has to awaken her every 4 hours to feed, and she will take only an ounce of formula at a time. She also is concerned that the infant has persistently hard, pellet-like stools. On your examination you find an infant with normal weight and length, but with an enlarged head. The heart rate is 75 beats per minute and the temperature is 35°C (95°F). The child is still jaundiced. You note large anterior and posterior fontanelles, a distended abdomen, and an umbilical hernia. This clinical presentation is likely a result of which of the following?

197) A 6-year-old Caucasian boy is brought to the emergency room by his mother with hemiplegia of acute onset. She states that she found the boy unconscious in his room where she had left him playing several minutes ago; and, he slowly gained consciousness, but could not move his right arm and leg. His past medical history is insignificant. Physical examination reveals right hemiparesis with little sensory abnormalities. No meningeal signs are present. The motor function restored spontaneously during 24-hour observation in the hospital. A CT scan of the head is normal. What is the most probable cause of this patient's problem?

198) A 6-year-old female with Down syndrome is brought to the physician for behavioral changes. Over the past few weeks, she has begun refusing to do her usual activities. Her parents also report that she seems dizzy and state that she has developed urinary incontinence. On examination, she is hypotonic but hyperreflexic with a positive Babinski reflex. Her gait is ataxic. Which of the following is the most likely diagnosis?

199) An 8-year-old Cub Scout who returned from an outing 9 days ago is brought to the clinic with the rapid onset of fever, headache, muscle pain, and rash. The maculopapular rash began on the flexor surfaces of the wrist and has become petechial as it spread inward to his trunk. Which of the following is the most likely diagnosis?

200) A 12-year-old girl has had a sore throat over 2 days. She now has a fever of 39.5°C and has difficulty opening her mouth, swallowing, or speaking. Her throat can be visualized with difficulty, the right tonsil is significantly more enlarged than the left, and the uvula is displaced to the left side. Which of the following is the most likely diagnosis?