PEDIATRIE USMLE 501-600

501. 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?

502. 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?

503. 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?

504. After 10 days of nasal congestion and rhinorrhea, a 3-month-old infant develops a severe hacking cough during which he repeatedly turns dusky and appears to choke on or to vomit profuse thick, clear nasopharyngeal mucus. For 7 days, the coughing continues unabated. On physical examination, he is afebrile and his lungs are clear. His chest x-ray is normal. His WBC count is 24,000/mm3, with 15% polymorphonuclear cells, 82% lymphocytes, and 3% monocytes. Which of the following antibiotics should be used to treat this patient?

505. 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?

506. A 6 month old male is brought in to the Emergency Room by his mother who states that when she picked him up from the baby-sitter he was not acting right. The baby-sitter stated that he was sleeping more and was fussy. On examination the baby is stuporous. His temperature is 37.8 C (99.9 F), pulse is 140/min, and respirations are 36/min. A 4 cm ecchymosis is noted on his right cheek. The remainder of the physical examination is unremarkable. The physician suspects possible physical abuse. He orders a CT scan of the head, skeletal survey, chemistry panel and complete blood count. Which of the following diagnostic tests should also be ordered?

507. 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?

508. A 12-year-old girl comes to the physician for an annual examination. She has been in good health for the past year and has no complaints. She began having menses this year and, after a few irregular cycles, is now having a monthly period. Past medical history is significant for multiple episodes of otitis media as a child. Past surgical history is unremarkable. She takes no medications and has no known drug allergies. Physical examination is unremarkable. If not currently immune, which of the following immunizations should this patient most likely receive?

509. A 4-week-old boy presents with a 10-day history of vomiting that has increased in frequency and forcefulness. The vomitus is not bile stained. The child feeds avidly and looks well, but he has been losing weight. An ultrasound of the abdomen is shown. Which of the following is the most likely diagnosis?

510. 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?

511. 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?

512. 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?

513. 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 11 8/78 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?

514. A 4-week-old male infant is brought to the office due to several episodes of projectile vomiting for the last few days. The vomitus contains milk and doesn't contain bile or blood. The child's appetite has increased for the last few days. He has been fed with goat's milk since birth, but doesn't seem to tolerate it anymore for the last few days. He vomits a few minutes after feedings. He appears dehydrated, and abdominal examination reveals no mass. Blood tests reveal macrocytosis. What is the most appropriate next step in the management of this patient?

515. A 6-year-old Hispanic boy is brought to your office by his mother because of severe pain in his right hip and refusal to walk for the last 2 days. His blood pressure is 100/70 mm Hg, pulse is 90/min, respirations are 18/min, and temperature is 38.7C (102.7F). His WBC count is 19,000/mm3 and ESR is 55 mm at one hour. On examination, he keeps his right hip externally rotated, and cries out in pain on any movement involving the right hip. Joint aspiration reveals a turbid fluid with total WBC: 90,000/mm3 and numerous bacteria. What is the most appropriate management in this patient?

516. A 6-week-old child arrives with a complaint of “breathing fast” and a cough. On examination you note the child to have no temperature elevation, a respiratory rate of 65 breaths per minute, and her oxygen saturation to be 94%. Physical examination also is significant for rales and rhonchi. The past medical history for the child is positive for an eye discharge at 3 weeks of age, which was treated with a topical antibiotic drug. Which of the following organisms is the most likely cause of this child’s condition?

517. 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?

518. A 4-year-old child is brought to the emergency department after he ingested liquid oven cleaner. His vital signs are stable. He is crying and drooling with blood-tinged secretions. His lips and chin are swollen and erythematous. His clothes are contaminated with the material. His breathing appears normal. His lungs are clear. Based on these findings, what is the best next step in the management of this patient?

519. A male infant is born to a primigravid woman whose pregnancy was uneventful. The delivery was uncomplicated. Physical examination of the newborn reveals deformity of the feet, specifically adduction of the anterior aspect of the foot with a convex lateral border and concave medial border. The ankle movements are normal, and passive and active movement of the foot overcorrects the deformity into abduction. AP radiographs reveal mild adduction of the metatarsals at the tarsometatarsal articulation, and an increased angle between the 1st and 2nd metatarsals. What is the best next step in the management of this patient?

520. You are called to a delivery of a term infant, about to be born via cesarean section to a mother with multiple medical problems, including a 1-month history of a seizure disorder, for which she takes phenytoin; rheumatic heart disease, for which she must take penicillin daily for life; hypertension, for which she takes propranolol; acid reflux, for which she takes aluminum hydroxide; and a deep venous thrombosis in her left calf diagnosed 2 days ago, for which she was started on a heparin infusion. The obstetrician is concerned about the possible effects of the mother’s multiple medications on the newborn infant. Which of the following medications is most likely to cause harm in this newborn infant at delivery?

521. 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 skin color?

522. 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?

523. A 4-year-old boy falls from the jungle gym at preschool. He sustains minor abrasions and contusions, and is taken care of by the school nurse. His parents take him that same afternoon to his regular pediatrician and demand "a thorough check-up" for possible internal injuries. The pediatrician complies, and a complete physical examination is normal. His hemoglobin is 14 g/dL, and a urinalysis shows the presence of microhematuria. Which of the following is the most appropriate next step in management?

524. A 9-year-old boy is brought to the pediatric clinic by his mother, who noticed that the left side of his mouth has started to droop over the past several days. In addition, he is unable to close his left eye completely and complains of it burning. Review of systems reveals a cold approximately two weeks ago and recent decreased taste sensation. Physical examination reveals a well nourished male with normal vital signs. There is left eye ptosis and mild erythema of the left conjunctiva. His smile is asymmetrical on the left. Laboratory evaluation, including a complete blood count and chemistry profile, are normal. Which of the following infections is most closely associated with this patient's condition?

525. A 5-year-old girl is brought to the physician with low grade fever and rhinorrhea. Her symptoms began ten days ago. She has also had persistent purulent rhinorrhea, nasal congestion, and a dry cough during the day that worsens at night. Her symptoms do not seem to be improving. On examination, the child has erythema and swelling of the nasal turbinates with purulent nasal drainage. She has evidence of drainage in the posterior pharynx as well. The remainder of her examination is unremarkable. Computed topography of her face is shown below. Which of the following is the most common predisposing factor for her condition?

526. A 1-week-old previously healthy infant presents to the emergency room with the acute onset of bilious vomiting. The abdominal plain film in the emergency department (A) and the barium enema done after admission (B) are shown. Which of the following is the most likely diagnosis for this patient?

527. A 3-year-old child presents to your office for an evaluation of constipation. The mother notes that since birth, and despite frequent use of stool softeners, the child has only about one stool per week. He does not have fecal soiling or diarrhea. He was born at term and without pregnancy complications. The child stayed an extra day in the hospital at birth because he did not pass stool for 48 hours, but has not been in the hospital since. Initial evaluation of this child should include which of the following?

528. A 3-month-old boy is brought to the pediatrician because of a red growth on his arm. The pregnancy had been uncomplicated, and the infant has been meeting all development milestones. He has been healthy so far and has received all scheduled immunizations. He is currently being breast-fed. His skin was clear at birth, but when he was 2 months old, his mother noted a light red growth on his arm. Within the past month, it has increased in size and has turned bright red. Which of the following is the most appropriate treatment for this disorder?

529. A 2-year-old boy is hospitalized for severe pneumonia requiring endotracheal intubation and mechanical ventilation. His hemoglobin level is 13.2 mg/dl and his WBC count is 3,200/mm3. The absolute level of CD3- positive lymphocytes is normal but the level of CD 19-positive lymphocytes is very low. This patient would benefit most from which of the following as a maintenance therapy?

530. 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:

531. A 2-week-old boy in the neonatal intensive care unit had a birth weight of 1200 g. Ultrasound of the head reveals grade II intraventricular hemorrhage and periventricular leukomalacia. An ophthalmologic examination reveals retinopathy of prematurity of both eyes. In addition, a hearing screen demonstrates bilateral hearing deficits. Which of the following is the most important determinant of this child's neurodevelopmental outcome?

532. 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?

533. A 15-month-old boy is brought to the ER because of fever and a rash. Six hours earlier he was fine, except for tugging on his ears; another physician diagnosed otitis media and prescribed amoxicillin. During the interim period, the child has developed an erythematous rash on his face, trunk, and extremities. Some of the lesions, which are of variable size, do not blanch on pressure. The child is now very irritable, and he does not interact well with the examiner. Temperature is 39.5°C (103.1°F). He continues to have injected, immobile tympanic membranes, but you are concerned about his change in mental status. Which of the following is the most appropriate next step in the management of this infant?

534. The 3-year-old sister of a newborn baby develops a cough diagnosed as pertussis by nasopharyngeal culture. The mother gives a history of having been immunized as a child. Which of the following is a correct statement regarding this clinical situation?

535. 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?

536. A 3-year-old boy is brought by his father to the Emergency Department with fever, headache and neck pain that developed over the past several hours. The father states he is not the birth father, and that he and his wife adopted the boy at 18 months of age after his birth mother abandoned him. Physical examination reveals a lethargic male with a temperature of 39.7 C (103.5 F). There is photophobia, and mildly injected conjunctiva are appreciated. Pupils are equal and reactive and funduscopic examination is unremarkable. The patient has neck stiffness with a positive Kernig's sign. A complete blood count reveals a leukocyte count of 24,000/mm3 with 64 segmented neutrophils and 25 bands. A lumbar puncture is performed that reveals elevated CSF pressure, decreased glucose, and elevated protein. A Gram's stain shows gram-negative pleomorphic rods. There is no growth on blood agar. Growth on chocolate agar reveals white colonies. Which of the following is the most likely pathogen?

537. A 16-month-old girl is brought to medical attention because of irritability, poor feeding, and temperatures up to 39.4 C (103 F). Careful history and physical examination fail to disclose any identifiable cause of her fever. There is some degree of abdominal tenderness on palpation. Which of the following is the most appropriate next step in diagnosis?

A premature neonate with respiratory distress syndrome is maintained on mechanical ventilation in a neonatal intensive care unit. Two weeks after delivery, the nurses in the intensive care unit notice that higher ventilation settings are needed and that more secretions are being suctioned from the endotracheal tube. A chest x-ray film shows questionable new infiltrates. Which of the following is the most likely pathogen?

539. A 2-year-old boy is brought to the emergency department (ED) in acute respiratory distress. He is afebrile, and has a heart rate of 100/min, respiratory rate of 80/min, and Sa02 of 84% on room air. He is sitting upright, and has significant nasal flaring and intercostal retractions. He is given supplemental oxygen in the ED. Chest x-ray reveal hyperinflation of the right lung, mediastinal shift to the left, and a severely hypoinflated left lung Which of the following is the most appropriate next step in management?

540. A 2-year-old presents to the emergency center with several days of rectal bleeding. The mother first noticed reddish-colored stools 2 days prior to arrival and has since changed several diapers with just blood. The child is afebrile, alert, and playful, and is eating well without emesis. He is slightly tachycardic, and his abdominal examination is normal. Which of the following is the best diagnostic study to order to confirm the diagnosis?

541. 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?

542. 25. The 1-year-old brother of a child with known abetalipoproteinemia is evaluated by a pediatrician for the disease. The 1 -year-old has been exhibiting steatorrhea and ataxia. Which of the following would most strongly support the suspected diagnosis?

543. 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?

544. 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?

545. 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?

546. The 4-year-old child pictured below is noted to have the tooth decay as shown. This characteristic pattern of tooth decay is caused by which of the following?

547. A 5-month-old infant is brought to the office for the evaluation of persistent vomiting, failure to thrive, and developmental delay. His antenatal and postnatal histories are not known to his Caucasian foster parents, who adopted him when he was 4 months old. The physical examination reveals an infant with blonde hair, fair skin and blue eyes. His urine has a peculiar musty odor. His plasma phenylalanine level is 40 mg/dl and tyrosine level is normal. His urinary phenylpyruvic and a-hydroxy phenylacetic acid levels are both increased. What is the most likely etiology of this child's symptoms?

548. A 2 1/2-year-old child is evaluated by a neurologist because of difficulty walking. Neurological examination documents ataxia and mental retardation. The neurologist notes the presence of multiple telangiectasias involving the conjunctiva, ears, and antecubital fossae. The child also has a history of multiple respiratory tract infections. Immunoglobulin studies on the child would most likely demonstrate an absence of which of the following?

549. A 15-year-old boy with Duchenne muscular dystrophy is brought to the emergency department with increasing respiratory distress and cyanosis. On examination, he is diaphoretic, with gasping respirations, poor air entry, and diminished responsiveness. He is tachycardic at 160 beats/min. His chest x-ray film shows a lingular pneumonia, and he is intubated. He improves over the next 10 days with antibiotics but is not extubated secondary to hypoventilation on weaning because of muscle weakness. Which of the following modalities will most likely help wean him off the ventilator?

550. A 2-year-old child presents to the office with a paternal complaint of “bowlegs.” The girl has always had bowlegs; her previous pediatrician told the family she would grow out of it. Now, however, it seems to be worsening. Her weight is greater than 95% for age, and she has significant bowing out of her legs and internal tibial torsion; otherwise, her examination is normal. A radiograph of her lower leg is shown. Which of the following is the most likely diagnosis?

551. A 14-year-old high school student arrives to your clinic for well-child care. In reviewing his records you determine that his most recent immunization for tetanus was at 4 years of age. Which of the following should you recommend?

552. A 20-month-old male is brought to ER with high fever, confusion and a skin rash suggestive of measles. He has a history of recurrent respiratory infections over the last 6 months. The patient's family has recently emigrated from a rural Russian province. Which of the following forms of vitamin supplementation should be considered in this patient?

553. A 3-year-old male is brought to the emergency department for evaluation of right neck swelling. His parents noticed a lump on his right neck yesterday, which has since increased in size and is now erythematous and tender. He has been previously healthy except for mild upper respiratory tract symptoms last week. His temperature is 38.0 0C (100.4 0F), pulse is 90/min, and respiratory rate is 25/min. On examination, he is nontoxic appearing. A 5-cm anterior cervical lymph node is palpated on the right side. It is poorly mobile, warm, erythematous, and tender to palpation. There is no fluctuance or induration. What is the most likely organism causing these symptoms?

554. A 5-year-old boy is brought into the ER immediately after an unfortunate altercation with a neighbor’s immunized Chihuahua that occurred while the child was attempting to dress the dog as a superhero. The fully immunized child has a small, irregular, superficial laceration on his right forearm that has stopped bleeding. His neuromuscular examination is completely normal, and his perfusion is intact. Management should include which of the following?

555. Aunt Mary is helping her family move to a new apartment. During the confusion, 3- year-old Jimmy is noted to become lethargic. The contents of Aunt Mary’s purse are strewn about on the floor. In the ER, the lethargic Jimmy is found to have miosis, bradycardia, and hypotension. He develops apnea, respiratory depression, and has to be intubated. His condition would most likely benefit from which of the following therapies?

556. As a city public health officer, you have been charged with the task of screening high-risk children for lead poisoning. Which of the following is the best screen for this purpose?

557. An infant is born at terrn to a 27-year-old Caucasian female. The prenatal course was uncomplicated. The amniotic fluid is clear. Immediately after the delivery, the infant starts crying and is moving all four extremities actively. Heart rate is 140/rnin. He is making a grimace on the attempt to put the suction catheter into his nostrils. His body is pink, but extremities are cyanotic. Which of the following is the next best step in the management of the infant?

558. 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?

559. 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?

In the 2nd week of life, a previously healthy newborn develops diarrhea. The stools are watery and voluminous and continue even when the infant is fasting. Which of the following is the most likely pathogen?

561. A 17-year-old girl presents to the office with a 5-day history of a malodorous vaginal discharge. She is sexually active and uses condoms for sexual intercourse. On examination, a thin, white discharge is seen. A "fishy" odor is produced when KOH is added to the discharge. The vaginal fluid has a pH of 5. Which of the following is the most likely finding on a microscopic examination of the vaginal fluid?

562. A 9-month-old child comes in for a routine visit. She has had several episodes of otitis media in the past, but no major illnesses or hospitalizations. Her mother is concerned because the child was previously happy and social around other people, but now cries if her mother is not in the room. The child constantly wants to be held by her mother and becomes upset if her mother walks into the next room. Her grandmother keeps her during the day, and she now cries when her mother leaves her in the morning. Developmentally, she is crawling and waves bye-bye. She does not yet respond to her name or say words. She previously babbled but stopped several months ago. When you hide a toy with your hand, she lifts your hand to look for the toy. Which of the following is the best next step in the management of this child?

563. A 14-year-old boy is seen in the ER because of a 3-week history of fever between 38.3°C and 38.9°C (101°F and 102°F), lethargy, and a 2.7-kg (6-lb) weight loss. Physical examination reveals marked cervical and inguinal adenopathy, enlarged tonsils with exudate, small hemorrhages on the soft palate, a WBC differential that has 50% lymphocytes (10% atypical), and a palpable spleen 2 cm below the left costal margin. Which of the following therapies should be initiated?

564. A 2-year-old child is seen in the emergency center with a 10-day complaint of fever and a limp. The child has an elevated erythrocyte sedimentation rate (ESR) and the radiograph shown below. Which of the following statements about this child’s condition is correct?

565. A 12-year-old boy with cystic fibrosis presents to the emergency department with a 3- day history of severe coughing, which is productive of a yellow-greenish purulent sputum. He had fever and chills at home. He also complains of chest congestion and chest pain that is worse with coughing. On physical examination, his temperature is 39.6 C (103.2 F), blood pressure is 98/68 mm Hg, pulse is 102/min, and respirations are 24/min. He is noted to be lethargic. He has rales on the left lower lung field on auscultation, and chest radiography shows an infiltrate in the left lower lobe. Which of the following is the most appropriate initial antimicrobial therapy for this patient?

566. 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?

567. A 16-year-old African American male with sickle cell anemia presents complaining of a 1-week history of exertional dyspnea, fatigue, and generalized weakness. He denies fevers, chills, night sweats, or cough. His only medication is oxycodone for chronic pain. On physical examination, he weighs 68 kg (150 lbs) and is 168cm (66 in) tall His temperature is 36.7 0C (98 0F), blood pressure is 120/70 mm Hg, pulse is 76/min, and respirations are 18/min. All organ systems appear normal Laboratory studies show: Hematocrit 20% Mean corpuscular volume 110 fl Reticulocyte count 1.0% Which of the following is the most likely mechanism underlying these findings?

568. A 15-year-old female with a history of bipolar disorder and psychosis presents to her physician's office requesting a pregnancy test. Her last menstrual period was 2 months ago. She states that her menses usually occur every 30 days. She is sexually active with one partner and occasionally uses condoms. She is concerned because she has gained 10 pounds in the last two months, and also complains of breast tenderness and milky white discharge from both nipples. She denies headaches, nausea, vomiting, diarrhea, or fever. Her vital signs are normal. Physical examination is unremarkable. A urine pregnancy test is negative. Which of the following is most likely responsible for this patient's symptoms?

569. 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?

570. A 17 -year-old boy is brought to the emergency department by his father after the boy began threatening him at home. Over the last several months, the father reports, the boy has been increasingly abusive. He was recently involved in a fist fight at school. The boy states that there is nothing wrong. He is otherwise healthy. He denies alcohol use, but does admit to occasional marijuana use. On examination he has acne on his forehead and back and his hairline is receding. There is palpable tissue underneath his nipples bilaterally Heart and lung exams are normal. What substance is this boy most likely abusing?

571. A 9-month-old infant is brought to the emergency department with lethargy and tachypnea. He was healthy before developing fever and diarrhea four days ago. He has been taking some formula, but has had two to three episodes of diarrhea with each bottle. He has lost three pounds (1 .4 kg) since his routine check-up two weeks ago. He has had one wet diaper in the past twenty four hours. On examination, his temperature is 102.5F (39.1c), pulse is 200/min, respiratory rate is 42/min, and blood pressure is 70/45 mm Hg. He is lethargic with decreased tone and decreased deep tendon reflexes. His mucous membranes are dry. Cardiopulmonary exam reveals tachycardia and tachypnea. His abdominal exam is unremarkable. Capillary refill is four seconds. Laboratory results are shown below. Chemistry panel Serum sodium 165 mEq/L Serum potassium 4.5 mEq/L Chloride 108 mEq/L Bicarbonate 14 mEq/L Blood urea nitrogen (BUN) 20 mg/dl Serum creatinine 0.8 mg/dl Calcium 10.0 mg/dl Blood glucose 98 mg/dl Which of the following fluids should be used as a bolus in the resuscitation of this infant?

572. A 15-year-old otherwise healthy boy presents with a complaint of intermittent abdominal distention, crampy abdominal pain, and excessive flatulence. He first started noticing these symptoms when he moved into his father’s house, and his stepmother insisted on milk at dinner every night. He has normal growth, has not lost weight, and has no travel history. Which of the following is the most appropriate study to diagnose his condition?

573. A 6-week-old infant is admitted to the hospital with jaundice. Her outpatient blood work demonstrated a total bilirubin of 12 mg/dL with a direct portion of 3.5 mg/dL. Which of the following disorders is most likely to be responsible? a. ABO incompatibility

574. 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?

575. A 15-year-old boy with tall stature presents with decreased exercise tolerance over the past 2 months. He states that he used to play two games of basketball with no problem, but he now can play only one game. On physical examination, his weight is at the 25th percentile, and his height higher than the 95th percentile. He is thin and has a gangly body habitus. His fingers are long and thin. There is pectus deformity in his chest. His joints are hyperextensible. An ophthalmologic examination reveals mild subluxation of the lens. Which of the following is the most likely finding on an echocardiogram?

576. A 2-year-old arrives in the emergency center after having swallowed a button battery from one of her toys. She is breathing comfortably, without stridor. Radiographs show the battery to be lodged in the esophagus. Which of the following is the correct next step?

577. 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?

578. A previously healthy 2-year-old male is brought to the emergency department after experiencing a seizure-like episode. His parents report that he has been healthy with the exception of mild upper respiratory symptoms for the past 24 hours. During the episode, his parents state that he fell down and had rhythmic, jerking movements of his arms and legs. The episode lasted about three minutes. The patient was sleepy when the emergency personnel arrived. Vital signs are temperature 39 .2 c (102 .5 F), pulse 120/min, and respiratory rate 25/min. The patient is alert and oriented in the emergency department. On examination, there is mild rhinorrhea and the left tympanic membrane is erythematous, bulging, and poorly mobile. The neck is supple. A complete neurological exam is unremarkable. After treating this patient's fever, which of the following is the next best step in the management of this patient?

579. An awake, alert infant with a 2-day history of diarrhea presents with a depressed fontanelle, tachycardia, sunken eyes, and the loss of skin elasticity. Which of the following is the correct percentage of dehydration?

580. A newborn infant is brought to the nursery for evaluation after delivery. The mother reports that the pregnancy was uncomplicated, but she had only two prenatal visits. The infant was born via normal spontaneous vaginal delivery and required no resuscitation. The infant has hepatosplenomegaly on examination. While in the hospital, the infant requires treatment for anemia and hyperbilirubinemia. On subsequent examinations, the infant has clear rhinorrhea and ulcerative lesions on his feet. Which of the following congenital infections is most likely in this patient?

581. A 2 week post mature baby is born and immediately exhibits severe respiratory distress. Previously, green-tinged meconium was noted in the amniotic fluid. Which of the following is the most appropriate next step?

582. 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?

583. An 18-month-old infant is found with the contents of a bottle of drain cleaner in his mouth. Which of the following treatment options is most appropriate?

584. A 16-year-old male, despondent over a recent breakup, tries to commit suicide by taking an unknown quantity of an unknown material he found at home. He is brought to the emergency center by his parents within 30 minutes of the ingestion. For which of the following household materials and medications should he be given activated charcoal as part of his emergency center treatment?

585. A 3-year-old African American boy is brought to the emergency department with sudden onset of difficulty walking. His mother reports that his right hand also seems "clumsy." The boy's past medical history is significant for a hospitalization one year ago for severe upper extremity pain and hand swelling. On physical examination, he has a blood pressure of 90/60 mmHg, heart rate of 120/min, temperature of 36.7°C (98°F), and respiratory rate of 22/min. Which of the following would be most helpful in diagnosing his condition?

586. A 25-year-old woman comes to your office for counseling. She says that her husband has cystic fibrosis, and that she has no family history of this disease. They are planning to have a child. She wonders what the probability is for their baby to have cystic fibrosis. Which of the following is your best response in this situation?

587. A 7-year-old boy is brought to the physician because of persistent nasal obstruction for 6 months. There is no: personal or family history of allergic disorders, Examination of the nasal fossae reveals bilateral ethmoidal polyps that protrude into the middle meatus and nasal cavity. Which of the following is the most appropriate next step in diagnosis?

588. 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?

589. The delivery of a newborn boy is remarkable for oligohydramnios. The infant (pictured) is also noted to have undescended testes and clubfeet, and to be in respiratory distress. Which of the following is the most likely diagnosis to explain these findings?

590. 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?

591. A 10-year-old presents with 2months history of heavy menstrual-like bleeding. Menarche occurred 6 months ago and this first menses consisted of spotting for 3-4 days without cramps. Subsequent periods were light in flow but lasted 6 to 8 days. Which of the following is the most likely cause of her bleeding?

592. A 4-year-old boy presents with 5-day history of fever and increased irritability. His temperature is 40. 2 C (104. 3 F), blood pressure is 98/68 mm Hg, pulse is 112/min, and respirations are 24/min. On physical examination, he is noted to have bilateral cervical lymphadenopathy, cracked lips, strawberry tongue, and bilateral conjunctival injection. His palms and soles are erythematous. There is a polymorphous macular rash generalized on his body. Which of the following is the most appropriate pharmacotherapy?

593. A 13-year-old male is brought to the physician for evaluation of intermittent left knee pain that arose three months ago. He does not remember any trauma to his knee. The pain worsens after basketball games, but improves some with rest. He has been taking non- steroidal anti-inflammatory medications with some relief. On physical examination, he has edema and tenderness over the proximal tibia at the site of the patellar tendon insertion. Examination of the knee joint is normal and no effusion is present. His knee pain is reproducible by extending the knee against resistance. A lateral radiograph of his knee is shown below. Which of the following is the most likely cause of this patient's knee pain?

594. A 4-day-old infant is brought to the physician for an outpatient follow-up visit. The mother's pregnancy and delivery were uncomplicated. The infant weighed 3.4kg (7 .5 lb) and was 19 in (48.2 cm) long at birth. He did well in the newborn nursery and was discharged from the hospital on day 2 of life. Today his mother reports that he is exclusively breastfed, and nurses for 10 minutes every 3 hours. He has 3-4 wet diapers a day, and has not had a bowel movement for two days. On examination, he weighs 2.95 kg (6.5 lb) and is 19 in (48.2 cm) long. He appears jaundiced on the face and chest. The remainder of the physical examination is unremarkable. Laboratory values are shown below. Total bilirubin 15 mg/dl Direct bilirubin 1 mg/dl Infant's blood type O positive Mother's blood type A positive Which of the following is the most likely cause of this infant's hyperbilirubinemia?

595. A 16-year-old boy with a history of ulcerative colitis presents to the physician complaining of diarrhea and a rash. He states that his appetite has been decreased recently, and also complains of nausea and abdominal pain in addition to watery diarrhea. He has an erythematous rash on his distal arms and legs that "burns". His mother reports that he has had poor concentration and has been irritable lately. Vital signs are stable. Examination reveals a beefy red tongue that appears swollen. Abdominal examination is normal. The rash resembles a sunburn and is located on his distal arms and legs. It is symmetrical and tender to palpation. Neurological examination is normal. This patient's symptoms are most likely due to a deficiency of which of the following vitamins?

596. You are called by a general practitioner to consult on a patient admit- ted to the hospital 4 days ago. The patient is a 7-month-old white boy with poor weight gain for the past 3 months, who has not gained weight in the hospital despite seemingly adequate nutrition. You take a detailed diet his- tory from his foster mother, and the amounts of formula and baby food intake seem appropriate for age. Physical examination reveals an active, alert infant with a strong suck reflex who appears wasted. You note generalized lymphadenopathy with hepatomegaly. In addition, you find a severe case of oral candidiasis that apparently has been resistant to treatment. Which of the following is the most appropriate next step in the evaluation or treatment of this child?

597. A 5-year-old boy presents with the severe rash shown in the photographs. The rash is pruritic, and it is especially intense in the flexural areas. The mother reports that the symptoms began in infancy (when it also involved the face) and that her 6-month-old child has similar symptoms. Which of the following is the most appropriate treatment of this condition?

598. A 13-year-old girl returns to her physician for followup of a strep throat, for which she had been treated 3 weeks previously. After performing a throat culture, the physician asks how school is going. There is dead silence. Her mother says that her daughter has missed the last 4 weeks of school. Which of the following is the most appropriate initial step in management?

599. A 1 -year old child is brought in for a well baby check-up. His parents report that he has been of good health and began walking a few weeks earlier. They are concerned that he tends to bump into things and falls more than his older sister did. Family history is significant for retinoblastoma. On examination, the pediatrician notes leukocoria of the left eye. No significant lymphadenopathy is present, and there is no enlargement of the liver or spleen. The child's height and weight are normal for age. Which of the following is the most appropriate next step in management?

600. 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?