USMLE_pediatry (376-500)

376. A 24-month-old child is seen in the pediatrician's office for a regular health supervision visit. He has no history of developmental delay. He was born by an uncomplicated normal vaginal delivery at term, and he has not had any significant illness or injury prior to this visit. Which of the following motor milestones is most consistent with his age?

377. A 2-year-old girl has severe dental caries of the upper and lower incisors. Her teeth are brushed twice daily with a small amount of fluoride-containing toothpaste. What is the feeding practice most likely to result in this pattern of dental caries?

378. A 6-year-old girl has a low-grade fever, headache, and nasal congestion. She has a flushed face and has developed a lacy reticular rash on the trunk and extensor surface of her arms and legs. Palms and soles are spared. Her mother has been ill with a low-grade fever and some joint stiffness and pain. Which of the following is the most likely diagnosis?

379. A 3-year-old boy has had fever for 4 days. On physical examination he has bilateral cervical lymphadenopathy, injected pharynx, and dry cracked lips. A throat swab is done and the rapid strep test is negative. The child is sent home and advised to follow-up if symptoms worsen. The child is brought back 2 days later with all previous findings including a maculopapular rash, swollen hands, and conjunctivitis. Which of the following is the most likely diagnosis?

381. A 6-year-old African-American child is brought in by his father for complaints of easy fatigability and pallor. These symptoms occurred after the son was treated with "some medication" for a recent diarrhea. Physical examination is normal except for pallor and multiple petechiae. Laboratory values are as follows: Hb 8.0 g/dL WBC 12,000/cmm Platelets 50,000/cmm Blood glucose 118 mg/dL Serum Na 135 mEq/L Serum K 5.3 mEq/L Chloride 110 mEq/L Bicarbonate 18 mEq/L BUN 38 mg/dL Serum creatinine 2.5 mg/dL Total bilirubin 3 mg/dL Direct bilirubin 0.5 mg/dL PT 12 seconds APTT 30 seconds LDH 900 IU/L Reticulocyte count 6% A peripheral blood smear reveals giant platelets and multiple schistocytes. What is the most likely underlying pathophysiology for this boy's pallor?

384. A 1-week-old infant is brought to the emergency department due to vomiting and poor feeding. The prenatal and birth histories are unremarkable. The infant's pulse is 140/min, temperature is 37 C (98.7 F), and capillary refill is 2 sec. He has sunken eyes, depressed anterior fontanel, and dry mucus membranes; skin elasticity is reduced. Heart and lungs are clear. There is no abdominal mass. Genital examination shows enlarged clitoris, and fusion of the labioscrotal folds. The initial laboratory work-up reveals the following: Sodium 128 mEq/L Potassium 5.8 mEq/L BUN 25 mg/dl If this patient's karyotype is 46 XX, which of the following is most likely to be increased in this patient's serum?

385. An 8 year-old Caucasian boy is brought to the office for the evaluation of high-grade fever, flank pain and burning micturition for the last two days. He has had two previous episodes of acute pyelonephritis. Physical examination reveals costovertebral angle tenderness. Urinalysis shows pyuria, significant bacteriuria, WBC casts, positive nitrite and esterase. The voiding cystourethrogram (VCUG) reveals vesicoureteral reflux. What is the most likely complication of this condition, if left untreated?

386. S woman comes to an emergency department because she is in labor. She has had no prenatal care. Her baby is delivered and appears to be of about 32 weeks' gestation. The newborn is very pale and shows severe, generalized edema. Cord-blood hematocrit is 22%, and cord-blood bilirubin is 7 mg/dl. Ultrasound examination demonstrates pleural effusions, ascites, cardiomegaly, and hepatomegaly. Which of the following is the most likely diagnosis?

387. A neonate is examined following a protracted breech delivery. One of the infant's arms is partially paralyzed. The affected arm is adducted and internally rotated at the shoulder, and the forearm is pronated. Which of the following is the most likely diagnosis?

388. A 2-year-old boy presents with refusal to use his right arm for 1 day. He is otherwise well. His mother states she pulled upward on his arm the previous evening to keep him from tripping down the stairs. Which of the following is the most likely diagnosis?

389. A 3-year-old male presents after having a tonicclonic seizure lasting about 1 minute. On examination, the child now has no neurologic abnormalities. He has a temperature of 40.3°C and has an obvious otitis media on the left but no other abnormalities on physical examination. You correctly counsel the family with which one of the following statements?

390. A 1-day-old infant who received silver nitrate eye drops in the delivery room is suffering from bilateral purulent conjunctival discharge. Which of the following is the most likely cause of this child’s condition?

391. A 10-month-old girl is seen in clinic for a routine checkup. She weighs 11 kg (24.2 lb). The infant's mother reports that she drinks whole cow's milk and takes solid food poorly. The infant's activity is decreased, but her muscle tone is good and her developmental milestones are up to date. The only significant abnormal physical finding is parlor. Which of the following is the most appropriate next step in management?

392. A 2-year-old boy is brought to the clinic because of a swelling at the base of his neck on the left side. The family indicates that since he was born, they suspected he had some kind of a mass in his left supraclavicular area and behind the sternomastoid on that same side, but the area felt soft and mushy, was not always evident, and seemed to be painless, so they did nothing about it. Two weeks ago the child had an upper respiratory infection, and within a day or two the mass became larger and quite obvious. On physical examination he indeed has a soft, mushy, ill-defined mass occupying the entire left supraclavicular area and extending into the posterior triangle of the neck. He has no enlarged lymph nodes anywhere, and his spleen and liver are not palpable. Which of the following is the most appropriate next step in the evaluation?

393. A 14-year-old girl has a history of red eyes with clear discharge that she suffers from in a seasonal pattern. Together with these symptoms, she reports itching, which is her most bothersome complaint. Physical examination shows conjunctival redness, tearing, and swelling, but there is no purulent discharge. This clinical picture is most compatible with a diagnosis of which of the following conditions?

394. A 4-day-old boy is brought to the physician for an outpatient follow-up visit. His mother's pregnancy and delivery were uncomplicated. The patient weighed 3.4 kg (7.5 lb) and was 48.2 cm (1'7") long at birth. He did well in the newborn nursery and was discharged from the hospital on day 2 of life. His mother reports that he is now exclusively breastfed and nurses for 10 minutes on each breast every 3 hours. He has two wet diapers/day and has not had a bowel movement for 2 days. He weighs 2.95 kg (6.5 lb) and is 48.2 cm (1'7'') long. He appears jaundiced on the face and chest. The remainder of the physical examination shows no abnormalities. Laboratory studies reveal: Total bilirubin 15 mg/dl Direct bilirubin 1 mg/dl Infant's blood type 0 positive Mother's blood type A positive Which of the following is the most likely cause of this infant's hyperbilirubinemia?

395. 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, ery1hematous, 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?

396. A young Hispanic couple brings their first child to their physician for a well-child examination. The child is a 3-month-old healthy-appearing infant, whose weight is at the 45th percentile of the normal growth curve. During examination, the physician observes an area of blue-black pigmentation over the buttocks. The parents say that it was present from the time of birth. Which of the following is the most appropriate next step in management?

397. A 14-year-old boy presents with decreased exercise tolerance. He is noted to have a grade III/VI systolic ejection murmur best heard at the left upper sternal border and a grade II/VI mid-diastolic murmur at the lower left sternal border. The first heart sound is normal. The second heart sound is widely split and fixed. A right ventricular impulse is palpated. On a chest roentgenogram, the pulmonary artery segment is enlarged, and pulmonary vascular markings are increased. An ECG shows right axis deviation. Which of the following congenital heart diseases does this boy most likely have?

398. A 7-year-old boy presents with a rash. His mother states that he was well until 3 days ago when he developed fever and malaise. The next day, the rash started as papules on the trunk, which rapidly changed to vesicles. The lesions have spread all over the body. On physical examination, he has no fever and seems well. You note numerous vesicles all over the body, some of which have crusted over. Which of the following is the most likely diagnosis?

399. A 7-year-old child is scheduled for an elective tonsillectomy. The most important instruction to the parents should be to make sure that the child does which of the following?

400. A 4-month-old baby is in for a well-child check and routine immunizations. The baby had a fever of 39°C the day he received his 2-month immunizations. The parents have read about the vaccine on the Internet and express their concerns. Which of the following is an absolute contraindication to giving the diphtheria and tetanus toxoids and acellular pertussis (DTaP)?

401. The mother and father of a newborn come in for the 2-week checkup. The mother complains of “colic” and asks if she can switch to goat’s milk instead of breast milk. Which of the following or cow’s milk? a. b. c. d. e. Should be your main concern about using goat’s milk instead of breast milk or cow's milk?

403. The mother of 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?

404. A routine prenatal ultrasound reveals a male fetus with meningomyelocele. The 24- year-old primigravid mother is told the infant will require surgery shortly after birth. You counsel her about the etiology of this defect and the risk of further pregnancies being similarly affected, and state which of the following?

406. A 7 -year-old African American boy is brought to your clinic with complaints of bedwetting. He was toilet trained at the age of 4. He has been able to pass urine normally in daytime, but has never been dry at night. There is no history of urgency or frequency during daytime. There is no history suggestive of child abuse. He had two episodes of urinary tract infections (UTI) from birth until he was 2-years-old, but he has not had any episodes ever since. What is the next best step in the management of this patient?

407. A 1-month-old male infant is brought to the emergency department by his mother due to a 3-day history of projectile vomiting. He has been formula- fed since birth, and his bowel movements are normal. He has never been ill before. His parents and 4-year-old sister are all healthy. One of his maternal uncles is mentally retarded. He weighs 3.1 kg (7 Ib). Physical examination reveals fair hair and skin, blue eyes, eczematous rash, and mild signs of dehydration. His urine has a mousy odor. What is the most appropriate screening test for this patient's early diagnosis and treatment?

409. You are advised by the obstetrician that the mother of a baby she has delivered is a carrier of hepatitis B surface antigen (HBsAg-positive). Which of the following is the most appropriate action in managing this infant?

410. You are asked to evaluate a 4-year-old boy admitted to your local children’s hospital with a diagnosis of pneumonia. The parents state that the child has had multiple, intermittent episodes of fever and respiratory difficulty over the past 2 years, including cyanosis, wheezing, and dyspnea; each episode lasts for about 3 days. During each event he has a small amount of hemoptysis, is diagnosed with left lower lobe pneumonia, and improves upon treatment. Repeat radiographs done several days after each event are reportedly normal. His examination on the current admission is significant for findings similar to those described above, as well as digital clubbing. Which of the following is the most appropriate primary recommendation?

411. A male infant, born to a 32-year-old white female, develops a bluish discoloration of the extremities and oral mucous membranes at 30 minutes of life. On examination, the infant is found to have tachypnea, nasal flaring and respiratory grunting. Auscultation reveals poor air entry on the left with a shift of cardiac sounds to the right. The abdomen has a scaphoid shape. The antenatal history is significant for polyhydramnios in the mother. The neonatologist on call suspects a diagnosis of congenital diaphragmatic hernia. What is the most appropriate next step in the management of this neonate?

412. A few weeks after a presumed viral respiratory infection, a 4-year-old girl presents with bruising and petechiae. Bone marrow examination reveals increased numbers of megakaryocytes but is otherwise normal. Hb is 13.5 g/100 mL. Platelet count is 30,000/mm3. Which of the following would be appropriate for this child at this time?

413. An 18-month-old child presents to the emergency center having had a brief, generalized tonic-clonic seizure. He is now postictal and has a temperature of 40C (104F). During the lumbar puncture (which ultimately proves to be normal), he has a large, watery stool that has both blood and mucus in it. Which of the following is the most likely diagnosis in this patient?

414. 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?

415. 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 A 6-year-old female with Down syndrome is brought to the physician for behavioral ataxic. Which of the following is the most likely diagnosis?

416. A 16-day-old infant presents with fever, irritability, poor feeding, and a bulging fontanelle. Spinal fluid demonstrates gram-positive cocci. Which of the following is the most likely diagnosis?

417. A 16-year-old boy presents to the emergency center with a 2-day history of an abscess with spreading cellulitis. While in the emergency center, he develops a high fever, hypotension, and vomiting with diarrhea. On examination you note a diffuse erythematous macular rash, injected conjunctiva and oral mucosa, and a strawberry tongue. He is not as alert as when he first arrived. This rapidly progressive symptom constellation is likely caused by which of the following disease processes?

419. A bat is found in the bedroom of a 4-year-old patient while the boy is sleeping. The family and the patient deny close contact with or bites from the bat. Which of the following is a correct statement regarding this situation?

420. 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?

421. A 10-year-old boy presents with red discoloration of the urine since the morning. He is healthy and otherwise asymptomatic. He denies dysuria, frequency, urgency, flank, or abdominal pain. His BP is normal. His examination is within normal limits including abdomen and genitourinary system. There is no rash or edema. His urine is pink in color; urinalysis is negative for hemoglobin or protein. No white cells, red cells, or bacteria are noted. Which of the following is the most appropriate next step?

422. 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?

423. A 2-year-old patient arrives late to your office with his father and a sign-language translator. They are very apologetic, but the father communicates that he had car trouble at his dialysis center and thus was late picking up the child from day care. The father is concerned about his child’s having intermittent red, bloody-looking urine. A gross inspection of the child’s urine in your office looks normal, but the dipstick demonstrates 3+ blood. Which of the following is the most likely cause of this child’s hematuria?

424. A 2-year-old boy is brought to the clinic by his mother because he is lethargic and not as active as the other kids on their block. He has difficulty walking and getting up, and he always appears tired. His mother thinks that she has a relative with a disorder that causes weakness. On examination, the child is alert but quiet. His calves appear hypertrophied. His reflexes are depressed. When he gets up from the floor, he uses his hands to climb on his legs to assume an upright position. What is the most likely diagnosis of this child?

425. A 2-month-old male infant is rushed to the emergency department by his baby sitter. She says that the baby became unresponsive and blue while feeding. The whole episode lasted 45-60 seconds, but the baby still appears pale. She denies any history of coughing or choking. On examination, the infant appears cyanotic and tachypneic. His blood pressure is 90/60 mm of Hg; his pulse rate is 155/min and regular. On auscultation, a harsh pansystolic murmur is noted at the left sternal border, along with a single S2. Hepatomegaly is noted. Pulse oximetry shows an oxygen saturation of 80%. Based on this history and physical examination, what is the most likely diagnosis?

426. A 9-year-old boy comes to the office for a pre-participation physical examination for summer camp. His parents report that he still has episodes of bed-wetting. The boy’s father confides that he also had bed-wetting until he was 10. They are concerned about the bed- wetting, but they are more concerned about their son’s upcoming week at summer camp and that the other boys may harass him for wetting the bed. Which of the following statements about nocturnal enuresis is correct?

428. During a routine well-child examination a 10-year-old girl reports that she has occasional headache, “racing heart,” abdominal pain, and dizziness. Her mother states that she has witnessed one of the episodes, which occurred during an outing at the mall, and reported the child to be pale and to have sweating as well. Other than some hypertension, she has a normal physical examination. Evaluation of this child is most likely to result in which of the following diagnoses?

430. A 20-month-old male is brought to the emergency department for evaluation of rectal bleeding after his parents discovered a substantial amount of maroon colored stool when changing his diaper. He has no history of hematochezia. The patient has been otherwise healthy and has not appeared to be in any pain. He has been eating and drinking well. His temperature is 3rC (98.6.F), blood pressure is 85/50 mmHg, pulse is 130/min, and respiratory rate is 20/min. On examination, the abdomen is soft, nondistended, and nontender. On rectal examination, there are no fissures or masses present. A fecal occult blood test is positive. The remainder of the physical examination is normal. Which of the following is the best test to confirm the diagnosis?

432. A 6-year-old boy is brought to your practice by his paternal grandmother for his first visit. She has recently received custody of him after his mother entered the penal system in another state; she does not have much information about him. You note that the child is short for his age, has downslanting palpebral fissures, ptosis, low-set and malformed ears, a broad and webbed neck, shield chest, and cryptorchidism. You hear a systolic ejection murmur in the pulmonic region. His grandmother reports that he does well in regular classes, but has been diagnosed with learning disabilities and receives speech therapy for language delay. His constellation of symptoms is suggestive of which of the following?

433. A 2-week-old infant is noted to be jaundiced. The baby's stools are pale, and his urine darkly colored. Physical examination demonstrates hepatomegaly. Serum studies show elevations of AST, ALT, conjugated bilirubin, and unconjugated bilirubin. By 2 months of age, the baby is notably irritated by pruritus, has retarded growth, and has visible dilated veins in the periumbilical area. Ultrasound fails to demonstrate a gallbladder. Which of the following is the most likely diagnosis?

434. A 3-year-old girl with a ventricular septal defect (VSD) presents to the emergency department after a 15-minute focal seizure of her left arm and leg. A brief history reveals that the child has no known seizure disorder and has been having a low-grade fever at home for about 4 days. She also has been less active and has had poor appetite. On physical examination, her temperature is 40.2 C (104.3 F), and her pulse is 82/min. She is not responsive to her name, but she is responsive to painful stimuli with withdrawal of her extremities. Cardiac examination is significant for a grade 3 systolic murmur best heard at the left lower sternal border. Neurologic examination reveals anisocoria with a dilated right pupil. After stabilization, which of the following is the most appropriate next step in diagnosis?

435. A mother brings her 7-year-old son to the clinic because, over the past several days, his urine has become pink and bis eyes have looked puffy. About 2 weeks ago, he missed school because of fever and a sore throat. On examination, the boy's blood pressure is 130/85 mm Hg, his eyelids and scrotum appear puffy, and he has 1+ tibial edema. No rashes are noted. Which of the following is the most likely diagnosis?

437. A 6-month-old child was noted to be normal at birth, but over the ensuing months you have been somewhat concerned about his slowish weight gain and his mild delay in achieving developmental milestones. The family calls you urgently at 7:00 AM noting that their child seems unable to move the right side of his body. Which of the following conditions might explain this child’s condition?

438. On a newborn boy’s first examination, you note a prominent occiput, a broad forehead, and an absent anterior fontanelle. The baby’s head is long and narrow. The remainder of the physical examination, including a careful neurological evaluation, is normal. You note that the baby was born via cesarean section for cephalopelvic disproportion. When you enter the mother’s room, the first question she asks is about her baby’s head shape. Which of the following is the most appropriate statement to the mother about this infant’s condition?

439. An 18-month-old male infant is brought to the office by his parents for a follow-up visit. He has a congenital condition that started at the age of 6 months with repeated vomiting and hypotonia, and progressively evolved into choreoathetosis, spasticity and dystonia. Over the past month, he has started biting his hands and arms, pinching himself and banging his limbs against the wall. His family history is unremarkable. On examination, he has several scars, cuts and bruises over his arms and hands. His uric acid levels are elevated. What is the most likely deficient enzyme in this patient?

440. You are asked by a colleague to evaluate a 5-year-old boy as a second opinion. He has a history of chronic and recurrent upper respiratory tract infections, several admissions to the hospital for pneumonia, and three surgeries for PE tubes for chronic otitis media. Of note is a right-sided heart on repeated radiographs. Convinced you know the diagnosis based on history alone, you confirm your diagnosis with a biopsy of the nasal mucosa. You expect to find which of the following?

441. A 13-year-old patient with sickle-cell anemia presents with respiratory distress; she has an infiltrate on chest radiograph. The laboratory workup of the patient reveals the following: hemoglobin 5 g/dL; hematocrit 16%; white blood cell count 30,000/μL; and arterial blood (room air) pH 7.1, PO2 35 mm Hg, and PaCO2 28 mm Hg. These values indicate which of the following?

442. An otherwise healthy 7-year-old child is brought to you to be evaluated because he is the shortest child in his class. Careful measurements of his upper and lower body segments demonstrate normal body proportions for his age. Which of the following disorders of growth should remain in your differential?

443. A 15-year-old girl is brought to the pediatric emergency room by the lunchroom teacher, who observed her sitting alone and crying. On questioning, the teacher learned that the girl had taken five unidentified tablets after having had an argument with her mother about a boyfriend of whom the mother disapproved. Toxicology studies are negative, and physical examination is normal. Which of the following is the most appropriate course of action?

444. A 4-year-old immigrant boy is brought by his mother to a Medical Camp for the Uninsured for the evaluation of his inflamed right eye. He has had a nasal discharge for the past 10 days. His brother has similar symptoms. His vital signs are stable. There are follicles and inflammatory changes in the conjunctiva of his right eye. The cornea shows neovascularization. What is the most likely diagnosis?

445. A previously healthy 7-year-old child suddenly complains of a headache and falls to the floor. When examined in the emergency room (ER), he is lethargic and has a left central facial weakness and left hemiparesis with conjugate ocular deviation to the right. Which of the following is the most likely diagnosis?

446. An irritable 6-year-old child has a somewhat unsteady but nonspecific gait. Physical examination reveals a very mild left facial weakness, brisk stretch reflexes in all four extremities, bilateral extensor plantar responses (Babinski reflex), and mild hypertonicity of the left upper and lower extremities; there is no muscular weakness. Which of the following is the most likely diagnosis?

447. A 5-year-old girl is diagnosed with Bordetella pertussis infection after an outbreak in the day-care center. She is prescribed erythromycin for 14 days. She lives with her parents and 13-year-old sister whose immunizations are up to date. What is the most appropriate way to limit the risk of infection in household contacts?

448. A 2-year-old boy is rushed to the emergency department by his 21-year-old white mother because he had a sudden-onset nosebleed which has now subsided. He never had any previous episodes. He is "sickly" and suffers from a productive cough and diarrhea that "refuses to go." His stools are greasy and foul-smelling. His appetite is normal, although his diet consists mainly of milk. His mother's boyfriend lives with them and is a chronic alcoholic. He was delivered vaginally without any complications. His weight is at the 25th percentile for his age. Physical examination reveals dry skin and dried blood at the nasal turbinates. What is the most likely cause of this child's failure to thrive?

449. A 6-year-old boy had been in his normal state of good health until a few hours prior to presentation to the ER room. His mother reports that he began to have difficulty walking, and she noticed that he was falling and unable to maintain his balance. Which of the following is the most likely cause for his condition?

450. A 9-year-old child has developed headaches that are more frequent in the morning and are followed by vomiting. Over the previous few months, his family has noted a change in his behavior (generally more irritable than usual) and his school performance has begun to drop. Imaging of this child is most likely to reveal a lesion in which of the following regions?

451. 6-month-old male is brought to the office due to fussiness and tugging at his right ear for the past 2 days. He has had a fever of 39.4° C (103° F) for the past 2 days. His past medical history is significant for recurrent ear and lung infections, oral candidiasis, and persistent diarrhea by rotavirus. His temperature is 39.4° C (103° F), pulse rate is 150/min, respirations are 28/min, and blood pressure is 80/60mm Hg. Physical examination reveals an ery1hematous, bulging right tympanic membrane with poor mobility on pneumatic otoscopy. His lymph nodes are not palpable, and his tonsils are not visualized. His B and T lymphocyte levels are markedly reduced. The chest x-ray reveals an absent thymic shadow. What is the most likely etiology of this patient's condition?

452. A 4-week-old boy is brought to clinic by his mother because of a 1day history of labored breathing. His birth was uneventful and immunizations have been up to date. His mother reports that the patient developed conjunctivitis on the fourth day of life. On physical examination, he is breathing rapidly at 40 breaths per minute and is afebrile. His chest reveals bilateral inspiratory crackles and a slight wheeze. On chest x-ray, bilateral pneumonia is evident. The leukocyte count is elevated at 15,000 with 40% eosinophils. Which of the following is the most likely pathogen causing the patient's symptoms?

453. A 15-year-old girl with type 1 diabetes mellitus presents to her primary care doctor for a routine check up. Perusal of her blood sugar chart indicates that her recorded blood glucose levels are routinely between 120 and 150 mg/dL before breakfast, dinner and bedtime, with the normal being 116 mg/dL. She is on NPH and regular insulin. Which of the following is the next appropriate step?

455. A previously healthy 5-year-old girl is brought to the emergency room from a camping trip because her parents are concerned about rabies. This morning, they found a bat in the child's tent. There were no obvious bite marks on the child. Afterwards, the girl helped her father clean animals he had brought back from a hunt, including squirrels, rabbits, and chipmunks. Later, while packing up the campsite, the child was bitten on the arm by a rat. Her encounter with which of the following animals most warrants post-exposure rabies prophylaxis?

456. A 1-year-old child is brought in for a regular "well baby" check-up. The child appears to have strabismus. The reflection of a bright light from the ceiling of the examination room comes from a different place in each eye. The family explains that the child has always looked that way, and there has been no recent change in the appearance of his eyes. Which of the following is the most effective management?

457. A 6-year-old boy presents in clinic for a routine visit. Examination reveals coarse, dark pubic hair, an enlarged penis and testes, and acne of the face and upper back. His mother notes that he has a body odor similar to that of her teenage son after playing sports. The child is in file 99th percentile of height for his age group. Which of the following is the most likely diagnosis?

458. A 10-year-old girl is brought to a pediatrician because her mother notices that she stumbles frequendy at night, even with adequate lighting. Visual field testing demonstrates a relatively narrow mid-peripheral ring scotoma. Ophthalmoscopy demonstrates dark pigmentation in a bone spicule configuration involving the equatorial retina. Additional findings include a waxy yellow appearance to the disk and narrowed retinal arteries. Which of the following is the most likely diagnosis?

459. A 6-week-old boy is brought to the physician because of a rash involving the diaper area. On examination, there are erythematous, slightly scaly patches covering the buttocks and the lower abdomen. Skin creases appear spared. The baby is otherwise healthy. Physical examination reveals no lymphadenopathy, fever, or other signs of organic illness. Which of the following is the most common cause of this condition?

460. A 1-day-old infant appears dusky in the newborn nursery during feeding. Oxygen is immediately administered by nasal cannula. Shortly afterward, she develops tachypnea. On physical examination, her blood pressure from the right upper arm is 50/30 mm Hg, her pulse is 180/min, and her respirations are 60/min. An echocardiogram is consistent with hypoplastic left heart syndrome. Which of the following would likely be found on auscultation?

461. A 3-year-old boy was bitten while teasing a neighborhood cat. On examination, there are two puncture wounds on the right hand and some superficial scratch marks. There is erythema, warmth, and induration around the puncture sites. Which of the following organisms most likely caused the infection?

462. A 5-week-old bottle-fed boy presents with persistent and worsening projectile vomiting, poor weight gain, and hypochloremic metabolic alkalosis. Of the following diagnostic modalities, which would most likely reveal the diagnosis?

463. A 16-year-old male is brought to the emergency department with a crush injury due to a farm accident. His immunization status is unknown. The wound is heavily contaminated with soil, and you are concerned about tetanus. Which of the following is the most appropriate management step?

464. Children with sickle cell anemia are at increased risk of developing overwhelming infection with certain microorganisms. Which of the following is the most reasonable step to prevent such infection?

465. A 14-year-old boy is brought to your office by his mother because of a two-week history of generalized edema, fatigue, and abdominal pain. His past medical history is insignificant, and the boy is not taking any medications. His BP is 110/70 mmHg and heart rate is 80/min. Urinalysis reveals proteinuria 4+, but urine sediment findings are within normal limits. Which of the following light microscopy finding would you expect in this patient's kidney biopsy?

466. While making rounds in the newborn nursery, the nurses ask you to examine a 2-day- old infant who is not feeding well. The nurse reports that the infant is irritable, is not sleeping well, and has had several episodes of vomiting and loose stools today. A review of the maternal history reveals that she had poor prenatal care and the pregnancy was complicated by intrauterine growth restriction. On examination, the infant is diaphoretic and has a high- pitched cry. The infant is also noted to have occasional sneezing and is mildly tachypneic. No dysmorphic features are noted and the remainder of the examination is unremarkable. This infant's symptoms are most likely caused by prenatal exposure to which of the following?

467. A 5-year-old child was hit in the right eye by a toy. He is rubbing at his eye, which is watering profusely. There is a small abrasion at the corner of the eye. He is mildly photophobic, but his pupils are equal, symmetric, and reactive to light and accommodation. His vision is normal. Which of the following is the most appropriate next step in the management of this patient?

468. A 9-month-old male is in for a well-child checkup. He is greater than 90th percentile for height, and he weighs 25 lbs. He no longer fits in his infant car seat, which is only recommended for use by children under 20 lbs. Which of the following is the safest car seat option for him?

469. A 2-year-old boy has had a purulent drainage from the right nostril for a week. He is afebrile and has had no associated symptoms, such as cough. Which of the following is the most likely diagnosis?

470. A 7 -year-old boy is brought to the office by his mother due to nocturnal enuresis. He has been wetting his bed at night for the past two years. He is otherwise healthy and has no psychological or behavioral problems. His mother is desperately asking for your help because she has tried alarms and bladder training, all to no success. What is the most appropriate next step in the management of this patient?

471. You are called to examine a male newborn because his first feeding caused him to choke, cough and regurgitate. He was born at term via normal vaginal delivery. On examination, he has excessive salivation, fine, frothy bubbles in the mouth, abdominal distention and rattling breath sounds. Radiographs of the chest and abdomen reveal bilateral atelectasis and gastric distension. Which of the following can best explain the above findings?

472. A 2 week-old neonate is brought to the office due to poor feeding and persistent vomiting. He had an episode of jerky movements of his limbs this morning. He was delivered at term with no complications and weighed 2.7kg (6 Ib) at birth. He appears lethargic, irritable and jaundiced. On examination, he weighs 2.2kg (5 Ib). His liver and spleen are enlarged. Bilateral cataracts are evident. Which of the following is most consistent with these findings?

473. A 9-year-old boy is brought to the office by his parents due to headaches, vomiting and visual disturbances. One week ago, he began to experience headaches that were most prominent in the morning. He also became lethargic, and had a decreased appetite and decline in school performance. The pertinent physical findings include an unbalanced gait, trunk dystaxia, horizontal nystagmus, and papilledema. If this child had a medulloblastoma, which structure would most likely be affected?

474. A 7 year-old-girl is brought to the clinic by her mother due to a persistent postnasal drip and repeated episodes of a runny nose. In the winter, she experiences several episodes of upper respiratory tract infections, which last for two to three weeks at a time. She snores, and is unable to smell her favorite food. Her immunizations are up-to-date. On examination, she is mildly underweight for her age. She has a runny nose, and her nasal drainage is colorless and stringy. Nasal inspection reveals bilateral nasal polyps, and auscultation of the chest reveals coarse rales. What is the one condition that you would like to rule out in this child?

475. A previously healthy 3 year-old-boy is brought to the emergency department (ED) due to stridor of sudden onset. Last night, he suddenly developed a high fever followed by breathing difficulty. His temperature is 40C (1 04F), pulse is 130/min, and respirations are 40/min. In the ED, the child is toxic-appearing, sitting up, leaning forward and drooling. His lungs are clear, and oxygen saturation is 85% in room air. What is the most appropriate next step in management?

476. A 2-week-old neonate is brought to the office due to poor feeding and persistent vomiting. He had an episode of jerky movements of his limbs this morning. He was delivered at term with no complications and weighed 2.7kg (6 Ib) at birth. He appears lethargic, irritable and jaundiced. On examination, he weighs 2.2kg (5 Ib). His liver and spleen are enlarged. Bilateral cataracts are evident. Which of the following is most consistent with these findings?

477. A 2-year-old boy is brought by his mother to the emergency department because of a high-grade fever which "does not go away" with acetaminophen. For the last four days, the child has been very irritable and is crying a lot. He is also pulling his ear and not eating well. He has been generally well, other than the occasional sore throat this season. His temperature is 38.8° C (102.2° F}, blood pressure is 90/60 mm Hg, pulse is 119/min, and respirations are 24/min. He appears well nourished, but is irritable. Physical examination reveals enlarged cervical lymph nodes and splenomegaly. The tympanic membranes are inflamed. CBC shows: WBC 81,100mm3 Hemoglobin 8.0 g/dL Hematocrit 25% Platelets 16,000 mm3 Blast forms 80% Prolymphocytes 10% Lymphocytes 10% The blast cells have condensed nuclear chromatin, small nucleoli and scant agranular cytoplasm. Subsequent histochemical staining reveals strongly positive periodic acid Schiff (PAS) reaction. No Auer rods were seen. Which of the following is the most likely diagnosis?

478. An 8-month-old infant arrives to the emergency department (ED) with a 2-day history of diarrhea and poor fluid intake. Your quick examination reveals a lethargic child; his heart rate is 180 beats per minute, his respiratory rate is 30 breaths per minute, and his blood pressure is low for age. He has poor skin turgor, 5-second capillary refill, and cool extremities. Which of the following fluids is most appropriate management for his condition?

479. During the examination of a 2-month-old infant, you note that the infant’s umbilical cord is still firmly attached. This finding prompts you to suspect which of the following?

480. You are seeing an established patient, 1 4-year-old girl brought in by her mother for vaginal itching and irritation. She is toilet trained and has not complained of frequency or urgency, nor has she noted any blood in her urine. Her mother noted she has been afebrile and has not complained of abdominal pain. Mom denies the risk of inappropriate contact; the girl also denies anyone “touching her there.” Your physical examination of the perineum is significant for the lack of foul odor or discharge. You do note some erythema of the vulvar area but no evidence of trauma. Which of the following is the most appropriate course of action?

481. A 16-year-old girl presents with a history of primary amenorrhea. On examination, short stature and a short neck with a low posterior hairline are noted. Chromosomal analysis most likely would reveal which of the following?

482. A 2-year-old child is brought to the emergency department with sudden onset of unresponsiveness, miosis, bradycardia, and muscle fasciculations. These findings are most suggestive of poisoning with which of the following?

483. A 2-year-old girl presents with fever of 39.3 C and irritability. She has had an upper respiratory tract infection for 4 days. On examination, the right ear is bulging and has poor movement on insufflation. Which of the following organisms is most likely responsible for these findings?

484. An infant is delivered vaginally to a 30-year-old G1P1 woman whose pregnancy was uneventful. Examination of the newborn reveals mild atrophy of the left calf. His left calcaneum and talus are in equinus and varus positions, his midfoot is in varus position, and his forefoot is in adduction. Dorsiflexion and plantar flexion of the ankle are limited. The neurologic examination is normal. What is the next best step in the management of this patient?

485. a 14-yeare-old boy is brought to your office by his mother because of a two-week-history of generalized edema, fatigue, and abdominal pain. His past medical history is insignificant, and the boy is not taking any medications. His BP is 110/70 mmHg and heart rate is 80/min. Urinalysis reveals proteinuria 4+, but urine sediment findings are within normal limits. Which of the following light microscopy finding would you expect in this patient's kidney biopsy?

486. A young infant is noted to have developed constipation over the past week, and then facial diplegia and difficulty sucking and swallowing. The child has been colicky, and the maternal grandmother has been treating the child with a mixture of weak tea, rice water, and honey. Which of the following disorders is the most likely culprit in this child?

487. At birth, an infant is noted to have an abnormal neurologic examination. Over the next few weeks he develops severe progressive central nervous system (CNS) degeneration, an enlarged liver and spleen, macroglossia, coarse facial features, and a cherry-red spot in the eye. Which of the following laboratory findings most likely explains this child’s problem?

488. A 3-year-old boy from a refugee camp is brought to the clinic for examination. His medical history is unknown. On examination, there is marked photophobia. He appears malnourished, and his weight is <5th percentile for age after hydration. His bones and ribs are prominent, and little subcutaneous fat is identified. His abdomen is concave with decreased bowel sounds. There is marked scaling and fissuring at the corners of his mouth, as well as inflammation and cracking of his lips. His tongue is atrophic. The tongue and oropharyngeal mucous membranes are dark red. Conjunctival pallor is present. There are pinkish-red, erythematous, scaly patches on his eyebrows, cheeks, and nose. This dermatitis is also present on the scrotal skin and extends onto the medial aspect of both thighs. Otherwise, his skin is very pale, and his fingernails and toenails are brittle. What is the most appropriate intervention for this patient?

489. 14-year-old boy comes to the offic because he has been feeling a mass under his right nipple for the last three weeks. The physical examination reveals clinical findings suggestive of right gynecomastia with very mild tenderness. The left breast and the rest of the physical exam is unremarkable. His testis is 2 cm in length and has 3 ml volume. What is the most appropriate next step in the management of this patient?

490. The parents of a 2-year-old bring her to the emergency center after she had a seizure. Although the parents report she was in a good state of health, the vital signs in the emergency center reveal a temperature of 39C (102.2F). She is now running around the room. Which part of the story would suggest the best outcome in this condition?

491. About 12 days after a mild upper respiratory infection, a 12-year-old boy complains of weakness in his lower extremities. Over several days, the weakness progresses to include his trunk. On physical examination, he has the weakness described and no lower extremity deep tendon reflexes, muscle atrophy, or pain. Spinal fluid studies are notable for elevated protein only. Which of the following is the most likely diagnosis in this patient?

492. A premature neonate develops respiratory distress syndrome several hours after birth. The infant is placed on a respirator and given other appropriate care. However, when the infant reaches a corrected gestational age of 36 weeks, he does not tolerate weaning from the ventilator. A chest x-ray film demonstrates alternating areas of hyperaeration and pulmonary scarring, resulting in parenchymal streaks and hyperexpanded areas. Which of the following is the most likely diagnosis?

493. Approximately 19 days after having had a severe sore throat, a 10-year-old girl is taken to a pediatrician because she is complaining that her arms and legs hurt. The mother reports that before the extremity pain began, the child had a rash with irregular boundaries that lasted about a day. Physical examination demonstrates mild fever, as well as swelling and erythema around several large joints. Laboratory studies show an elevated erythrocyte sedimentation rate, and ECG demonstrates a prolonged PR interval. Which of the following is the most likely explanation for these findings?

494. A neonate has Down syndrome. Maternal hydrammos had been noted prenatally. After the first feeding, the infant has projectile vomiting with bile-stained vomitus. An x-ray film demonstrates a "double-bubble sign" in the abdomen. Which of the following is the most likely diagnosis?

495. A 1 0-year-old boy is brought to the office by his parents because he is developing dark facial hair, deepening of the voice and a rapid height increase. He also complains of persistent headaches which are resistant to over-the-counter analgesics for the past 2 weeks. He denies nausea, vomiting or visual disturbances. His medical history is unremarkable. Physical examination reveals coarse pubic and axillary hair. Other pertinent findings include lid retraction, paralysis of upward and downward gaze, and poor pupillary reaction to light. His deep tendon reflexes are normal, Babinski sign is negative, and there are no focal neurologic signs. What tumor is most likely responsible for this child's symptoms?

496. A mother brings her daughter into the clinic for a routine heath-care visit. On examination, you note that she walks alone, knows two words, throws objects, and comes when called. What is the most likely age of this infant?

497. A 16-year-old Caucasian male presents to the office with pain and limited motion of the right knee. His right knee, as well as his right ankle, has swelled several times before. He has a history of easy bruising since childhood, and an episode of excessive bleeding after a tooth extraction. His uncle had similar problems. Which of the following is the most likely cause of this patient's joint pain?

498. A 17-year-old girl comes to the clinic with several weeks of joint pain and rash. The joint pain is most prominent in the hands. She states that the pain is most severe in the morning and tends to improve over the day. She has noted some swelling of her fingers. She has also had a rash on her face that becomes more prominent when she is outdoors. She states that sunlight tends to bother her eyes. On further questioning, she states that she has not felt well for several months. She has had intermittent fever, has been more tired than usual, and has lost weight although she has not been restricting her diet. On physical examination, she looks tired. She has lost 5 lbs since her last visit 1 year ago. She has an erythematous rash on her cheeks. She has several shallow ulcers in her mouth. She has fusiform swelling of her fingers and pain with movement of her fingers. Which of the following is the most likely diagnosis?

499. A full-term newborn develops cyanosis a few hours after birth. Oxygen administration does not improve color or oxygen saturations. Which of the following is the most likely diagnosis?

500. As part of your anticipatory guidance to new parents of a healthy new- born, you suggest putting the child in which of the following positions for sleep?