PEDIATRIE USMLE 601-700

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

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

603. A 6-year-old Asian boy is brought by his parents to the office due to high-grade fever and rash for the last 9 days. A brick-red, maculopapular rash first appeared on his face and subsequently spread to his trunk and extremities. Prior to the outbreak of the rash, he had a non-productive cough, tearing of eyes, runny nose, sneezing, and intermittent nasal obstruction. Laboratory findings are as follows: Hct 46% WBC 2,000/mm3 Platelets 160,000/mm3 Which of the following has been shown to reduce the morbidity and mortality rates of patients with this kind of infection?

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

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

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

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

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

609. A 15-year-old African-American girl has a facial rash and vague joint pains. Her temperature is 37.2C (99F). On examination, a malar erythematous rash is noted. Her laboratory evaluation is significant for anemia, leukopenia, and a normal platelet count. Her antinuclear antibody and Rapid Plasma Reagin (RPR) tests are positive. Which of the following tests is confirmatory for this patient's condition?

610. A 7 -year-old boy is rushed to the emergency department after falling on his outstretched hand. He immediately complained of right arm pain after the accident, and he currently cannot move his arm due to the pain. He is crying and holding his right arm in flexion. There is ecchymosis just above his elbow. He cries out in pain when his arm is moved. An x-ray reveals a supracondylar fracture. What secondary injury is most commonly associated with this patient's fracture?

611. A patient with hair loss is shown below. The lesion does not fluoresce with a Wood lamp and has not responded well to a variety of topical agents. The lesion is boggy, is spreading, and has tiny pinpoint black dots throughout. Which of the following is the most likely diagnosis?

612. An 8-year-old sickle-cell patient arrives at the emergency room (ER) in respiratory distress. Over the previous several days, the child has become progressively tired and pale. The child’s hemoglobin concentration in the ER is 3.1 mg/dL. Which of the following viruses commonly causes such a clinical picture?

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

614. A 5-year-old boy is brought to clinic with increasing right lower foot pain. He stepped on a nail several days ago. At that time, the family had sought medical attention. The child was given a tetanus shot, and the wound was extensively irrigated. On examination, the foot is tender, swollen, warm, and erythematous. Osteomyelitis is suspected. Which of the following is the most appropriate next step in diagnosis?

615. A 16-year-old girl with an incomplete vaccination record received one dose of the measles, mumps, and rubella (MMR) vaccine during a doctor's visit. One month later, she learns that she is 9 weeks pregnant, and she is concerned about potential birth defects resulting from the MMR vaccine. Which of the following most closely approximates the risk of birth defects secondary to MMR vaccine exposure during the first trimester?

616. A 6-week-old male infant who was born at 32 weeks' gestation with a birth weight of 1500 g, has had an average weight gain of 8 g/day since birth. He takes an iron-fortified formula that is 24 kcal/oz. His calorie intake is about 125 kcal/day. It is noted that his stool is poorly formed and bulky. Which of the following dietary modifications will most likely result in decreased steatorrhea and improved weight gain?

617. A previously healthy 4-year-old girl is brought to the office due to a 12-day history of persistent, thick, nasal discharge, nasal congestion, headache, cough, and intermittent low- grade fever. The cough is worse at night, but there is no wheezing. Her temperature is 37.2C (99F), pulse is 90/min, and respirations are 15/min. Examination shows an alert, interactive child breathing comfortably. She has clear tympanic membranes, congested posterior nasal pharynx with thick and purulent mucus, and red, swollen nasal turbinates. Her maxillary sinuses are mildly tender. Her lungs are clear on auscultation. What is the most appropriate next step in the management of this patient?

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

619. A 13-year-old comes to your office expressing concern about his height. He had first seen you a year prior for his routine checkup and a preparticipation sports physical for soccer (see growth curve). Now in the eighth grade, al of his friends are taller than he is, and he is at a disadvantage on the soccer field playing against much larger boys. After obtaining height information from his parents shown here, you order a skeletal bone age radiograph. Which of the following results would allow you to assure him of an excellent prognosis for normal adult height?

620. The parents of the child pictured below bring him to the office for evaluation of short stature. At 5 years of age, he is the shortest child in his kindergarten class. His development is normal, and he is reading on a first grade level. Both parents are of normal height, and this child resembles no one in the family. Which of the following is the most likely diagnosis?

621. A 3-day-old, full-term baby boy is brought into the emergency department because of feeding intolerance and bilious vomiting. X-rays films show multiple dilated loops of small bowel and a "ground glass" appearance in the lower abdomen. The mother has cystic fibrosis. Which of the following diagnostic tests would also have therapeutic value?

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

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

624. A 5-year-old boy develops a headache, cough, myalgia and a fever. He has been a healthy child with all immunizations up to date. He is given a decongestant and an aspirin for his symptoms with some relief. However, 4 days later, he is brought back by his parents because of persistent vomiting and irritability. On physical examination, he is found to be semicomatose, becoming combative on stimulation. Which of the following levels should be measured to aid in the diagnosis of this patient?

625. A 3-year-old boy is admitted for seizure-like activity. He has been a healthy child and has been meeting all development milestones. His immunization schedule is upto-date. Examination is notable for an erythematous throat and fever. His convulsions require IV administration of a benzodiazepine. Serum analysis reveals a normal white cell count with mild basophilic stippling. The lumbar puncture reveals elevated CSF pressure. Head CT scan is notable for cerebral edema. Which of the following is the next diagnostic step?

626. A 2-week postmature neonate exhibits severe respiratory distress immediately after birth. Previously, greentinged meconium was noted in the amniotic fluid. Which of the following is the most appropriate next step in management?

A 12-year-old girl has a solitary thyroid nodule found on routine examination; she has no symptoms. Which of the following is the most appropriate next step for this patient?

628. The 16-month-old male infant pictured below was recently brought from a developing country to the United States. The family history reveals that his father had an eye and a leg removed. Which of the following is the most likely diagnosis?

629. A 12-year-old African American boy is brought to the office due to a 2-day history of high-grade fever and chills. He was apparently well before the onset of fever. He has no bone pain. He has sickle cell disease and has had 4 hospitalizations for painful crises and one episode of osteomyelitis. His blood pressure is 90/60 mm Hg, pulse is 100/min, respirations are 22/min and temperature is 38.9 C (102F). He appears drowsy. His laboratory report shows a total WBC count of 16,000/mm3 with 12% bands and Hb of 9.0 g/dl. Which of the following is the most likely cause of this patient's condition?

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

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

632. A 7-day-old boy who is the product of an uncomplicated gestation is brought to the physician because of hypospadias. The baby is otherwise healthy, and is urinating without any difficulty. On physical examination, vital signs are stable, lungs are clear and the heart is beating at a regular rate. The only abnormal physical finding is the hypospadias. Urinalysis is negative for infection. Which of the following is the most appropriate next step?

633. A 15-year-old Caucasian boy is injured during a football game. He is taken to the emergency department for x-ray films of his leg to rule out a possible fracture. The radiologist reports that the boy has evidence of an aggressive bone tumor with both bone destruction and a soft tissue mass. Later, the pathologist reports that the bone biopsy reveals a bone cancer with some of the tumor tissue displaying neural differentiation. Which of the following is the most appropriate next step in management?

634. A 7-year-old boy has a history of repeated urinary tract infections that have been treated by the empiric use of antibiotics. The parents are not satisfied with the care the child is receiving, and they take him to a pediatric urologist. Evaluation by voiding cystourethrogram shows that the patient has vesicoureteral reflux without ureteral or upper tract dilatation (grade one reflux). Which of the following is the appropriate management for this child?

635. A 10-year-old boy was healthy until about 10 days ago when he developed 7 days of fever, chills, severe muscle pain, pharyngitis, headache, scleral injection, photophobia, and cervical adenopathy. After 7 days of symptoms he seemed to get better, but yesterday he developed fever, nausea, emesis, headache and mild nuchal rigidity. Cerebrospinal fluid (CSF) shows 200 white blood cells (WBC) per microliter (all monocytes) and an elevated protein. Correct statements about this infection include which of the following?

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

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

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

639. A 10-year-old male fell while riding his scooter down a steep hill. In the Emergency Department, his injuries included a fractured wrist and a lacerated spleen, which required surgical removal. Two years later he is diagnosed with bacterial pneumonia. Which of the following bacterial agents is the most likely pathogen for this patient's pneumonia?

640. A 15-year-old girl presents with diplopia after prolonged reading and ptosis that worsens in the afternoon. On examination, she is noted to have bilateral ptosis, impaired extraocular muscle movements, facial weakness, and generalized hypotonia and weakness increasing with repetition. Which of the following is the best diagnostic test for this disorder?

641. A 12-year-old boy presents to his pediatrician with frequent episodes of headache, nausea, blurry vision, and sweating. On physical examination, his temperature is 37.4 C (99.3 F), blood pressure is 148/94 mm Hg, pulse is 92/min, and respirations are 18/min. The rest of his examination is unremarkable. His 24-hour urinary vanillylmandelic acid (VMA) and metanephrines are increased. An abdominal CT reveals an extrarenal mass above the left kidney. Which of the following is the most appropriate pharmacotherapy?

642. A 12-year-old girl with mild asthma comes to the office for a health maintenance visit. Her mother states that she is using her albuterol inhaler 2-3 times a week and that she has a cough that wakes her up at night about 3 times a month. On physical examination, she has diffuse inspiratory and expiratory wheezes. She has no accessory muscle use. Pulse oximetry shows 95% oxygen saturation on room air. Which of the following is the most appropriate treatment for her at this time?

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

644. A 20-month-old child is brought to the ED because of fever and irritability and refusal to move his right lower extremity. Physical examination reveals a swollen and tender right knee that resists passive motion. Which of the following is the most likely to yield the diagnosis in this patient?

645. A 6-year-old boy is brought to the office by his mother for the evaluation of a "skin disease." The physical examination reveals multiple vesiculopustular lesions on his face and neck. Some lesions are colored golden-yellow and encrusted. The crust is thick and adherent to the underlying skin. The rest of his physical examination is within normal limit. What is the most appropriate treatment for his skin condition?

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

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

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

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

650. An 8-year-old boy presents to the pediatrician's office with a headache for the past 3 weeks. His mother also states that he has been more tired and has had frequent nose bleeding for the past month. On physical examination, his height and weight are both below the 5th percentile for his age. His blood pressure is 152/86 mm Hg in all four extremities. His pulse is 74/min, and respirations are 16/min. His heart examination is normal with no murmur. His peripheral pulses are strong and symmetric. Urinalysis and serum electrolytes are ordered. Which of the following is the most appropriate next step in diagnosis?

651. A 1-year-old presents for a well-child checkup, but the parents are concerned about giving the child his immunizations. Which of the following is a true contraindication to the administration of the fourth DTaP (diphtheria and tetanus toxoid and acellular pertussis) vaccine?

652. An 11-year-old boy presents with fever and sore throat. A rapid-strep test confirms streptococcal pharyngitis. He is leaving for a summer camp in 2 days. In the past, he has had problem finishing the whole course of antibiotic treatment. Which of the following is the best treatment for his streptococcal pharyngitis?

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

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

655. An 8-week-old female infant is brought to the office by her Caucasian mother for a well-baby examination. She was born at 34 weeks gestation, and weighed 2.9kg (6.51b) at birth. She has been exclusively breastfed since birth, and her growth and development are normal for her age. The physical examination is normal, except for mild pallor. At this time, what is the most appropriate nutritional intervention for this patient?

656. A 6-year-old boy is brought to the clinic due to persistent leg pain. Over the last few months, he has been constantly complaining of pain in his legs. The painful episodes occur only at night, and last a few hours each. His mother has been treating him with over-the- counter medications. He is able to walk and run to school without any complaints. He has no fever, chills and history of trauma. On examination, there is no obvious trauma to his legs, and the limb exam is completely normal. His parents are very worried and ask that you "do something.” Which of the following is the most appropriate next step in management?

657. Parents bring a 5-day-old infant to your office. The mother is O negative and was Coombs positive at delivery. The term child weighed 3055 g (6 lb, 1 oz) at birth and had measured baseline hemoglobin of 16 g/dL and a total serum bilirubin of 3 mg/dL. He passed a black tarlike stool within the first 24 hours of life. He was discharged at 30 hours of life with a stable axillary temperature of 36.5°C (97.7°F). Today the infant’s weight is 3000 g, his axillary temperature is 35°C (95°F), and he is jaundiced to the chest. Parents report frequent yellow, seedy stool. You redraw labs and find his hemoglobin is now 14 g/dL, and his total serum bilirubin is 13 mg/dL. The change in which of the following parameters is of most concern?

658. You are called to a delivery of a woman with no prenatal care; she is in active labor but has no history of amniotic rupture. The biophysical pro- file done in the emergency center revealed severe oligohydramnios. When you get this infant to the nursery, you should carefully evaluate him for which of the following?

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

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

661. A newborn infant becomes markedly jaundiced on the second day of life, and a faint petechial eruption, first noted at birth, is now a generalized purpuric rash. Hematologic studies for hemolytic diseases are negative. Acute management should include which of the following?

662. A 14-year-old girl, angry at her mother for taking away her MP3 player, takes an unknown quantity of a friend’s pills. Within the first hour she is sleepy, but in the emergency center she develops a widened QRS complex on her electrocardiogram (ECG), hypotension, and right bundle branch block. The therapy you would initiate for this ingestion is which of the following?

663. A 3-year-old boy of African descent is brought to your office by his stepfather because of easy bruising. He says that the child bruises easily even without trauma. The child started playing games by himself recently. He has a past history of clavicular fracture, which the stepfather attributes to a fall down a set of stairs. The history of the biological father is unknown. On examination, there is a right knee effusion with decreased range of motion, and multiple soft tissue hematomas on the thigh. What is the most appropriate diagnostic step in management?

664. An 8-year-old boy with sickle cell disease presents with left leg pain and a high fever. He has been refusing to walk since yesterday. On physical examination, his temperature is 39.8 C (103.6 F), blood pressure is 122/68 mm Hg, pulse is 102/min, and respirations are 20/min. His left femur is tender to palpation 3 cm above the left knee, and there is marked soft tissue swelling. A plain film of his left leg is normal. A bone scan shows increased uptake around the metaphysis of the left femur. Which of the following is the most likely pathogen?

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

666. A mother arrives to the clinic with her three children (ages 2 months, 18 months, and 36 months). The 18-month-old has an intensely pruritic scalp, especially in the occipital region, with 0.5-mm lesions noted at the base of hair shafts, as shown in the picture. Which of the following therapies should be avoided in this situation?

667. An infant born at term to a 22-year-old woman has a weak cry and is cyanotic at birth. His fingertips and oral mucosa appear blue. His blood pressure is 80/40 mmHg and his heart rate is 140/min. Chest x-ray shows clear lung fields bilaterally. PaO2 measured by arterial cannulation is 38 mmHg, and improves only minimally on 100% inspired oxygen. Which of the following is the best next step in managing this patient?

668. An 18-year-old male undergoes elective hernia repair. During the operation, he suffers considerable blood loss, and receives a blood transfusion. He then experiences an anaphylactic transfusion reaction. He is resuscitated and further hospital course is uncomplicated. His past medical history is significant for recurrent sinopulmonary infections and intermittent episodes of diarrhea since childhood. Which of the following is the most likely cause of his symptoms?

669. An 8-month-old previously preterm infant with bronchopulmonary dysplasia presents to the emergency department with lethargy. His regular medications include furosemide and spironolactone. His temperature is 37.4 C (99.3 F), blood pressure is 68/32 mm Hg, pulse is 110/min, and respirations are 10/min. He has poor skin turgor and dry mucous membranes. Laboratory chemistry evaluation reveals: sodium, 131 mEq/L; potassium, 3.0 mEq/L; chloride, 84 mEq/L; bicarbonate, 38 mEq/L; blood urea nitrogen, 36 mg/dL; and creatinine, 0.4 mg/dL. An arterial blood gas shows pH, 7.52; PaCO2, 49 mm Hg; and PaO2, 92 mm Hg. Which of the following is the most likely explanation for these findings?

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

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

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

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

674. A 24-month-old girl is brought to the pediatrician's office for evaluation because her mother noticed a yellowish discharge on the girl's underwear for the past 3 days. She had no fever, but her mother said she has been fussier recently. On physical examination, the girl is appears excessively anxious about contact with the physician. Her introitus is inflamed, and the hymeneal edge is jagged at the 8 o'clock position. A vaginal culture is taken. Which of the following organisms, if isolated from the vaginal vault, would constitute the most definitive evidence of sexual abuse?

675. You are called to the delivery room to evaluate an infant born at 28-weeks gestational age. The infant is tachypneic and cyanotic. Examination reveals intercostal and subcostal retractions along with nasal flaring. Lungs have coarse breath sounds bilaterally. After initial resuscitation, the patient is given respiratory support with continuous positive airway pressure and admitted to the neonatal intensive care unit. The patient's respiratory status continues to worsen over the next 24 hours. A chest radiograph from the patient is shown below. In addition to prematurity, which of the following is a risk factor for the development of this disease?

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

677. You are asked to evaluate an infant born vaginally 3 hours previously to a mother whose only pregnancy complication was poorly controlled gestational diabetes. The nursing staff noticed that the infant was breathing abnormally. On examination, you find that the infant is cyanotic, has irregular, labored breathing, and has decreased breath sounds on the right side. You also note decreased tone in the right arm. You provide oxygen and order a stat portable chest radiograph, which is normal. Which of the following studies is most likely to confirm your diagnosis?

678. 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 0c (101 0F), pulse 85/min, and respiratory rate 20/min. On examination, there is pain and stiffness during manipulation of the wrists and ankles. A faint, erythematous, centrifugal rash on her trunk and proximal limbs is present. Laboratory studies show: Complete blood count Hemoglobin 12.5 g/dL MCHC 32% MCV 85 fl Reticulocyte count 0.1% Platelet count 200,000/mm3 Leukocyte count 6,500/mm3 Neutrophils 56% Eosinophils 1% Lymphocytes 33% Monocytes 10% C- reactive protein 3.5 mg/dL Erythrocyte sedimentation rate 38 mm/hr Which of the following is the most likely diagnosis?

679. A 14-year-old African-American girl presents to the ER with a mild fever and severe right-sided thigh pain. She is agitated and requests quick pain relief. Her heart rate is 120/min and blood pressure is 120/70 mmHg. She says that she had a similar episode one year ago and was placed in the hospital for intravenous pain management. Her brother had similar episodes and died of an infection at 10 years of age. Which of the following would you most expect to see on this patient's peripheral blood smear?

680. A 9-year-old African-American boy is brought to ER with high fever, poor appetite, and irritability. His heart rate is 140/min and his blood pressure is 80/60 mmHg. He has been hospitalized several times before for poorly localized abdominal pain. He also has a history of hematuria. The boy has not received several routine vaccinations because his mother is afraid that they will cause autism. His hematocrit is 22% and the reticulocyte count is 12%. The patient dies several hours after the admission. This patient's death may have been prevented by:

681. A 10-month-old infant has poor weight gain, a persistent cough, and a history of several bouts of pneumonitis. The mother describes the child as having very large, foul- smelling stools for months. Which of the following diagnostic maneuvers is likely to result in the correct diagnosis of this child?

682. A 3-year-old girl is admitted with the x-ray shown below. The child lives with her parents and a 6-week-old brother. Her grandfather stayed with the family for 2 months before his return to the West Indies 1 month ago. The grandfather had a 3-month history of weight loss, fever, and hemoptysis. Appropriate management of this problem includes which of the following?

683. A previously healthy 18-month-old male comes to the physician for evaluation of fever. His mother reports that he has had a fever ranging from 1 02.2 0F (39.0 0c) to 104.0 0F 0c) for the past five days. He has also become increasingly irritable with decreased appetite. His mother reports that he does continue to take some liquids. There are no known sick contacts. On examination, the infant's temperature is 102.5 0F (39.2 0C), pulse is 120/min, and respiratory rate is 20/min. He is irritable during the examination. There is conjunctival erythema bilaterally, with serous drainage from both eyes. His oropharynx is erythematous and his lips are fissured. There is a 2 cm anterior cervical lymph node palpable on the right side. His neck is otherwise supple and he is able to flex his chin to his chest without difficulty. There is mild abdominal tenderness to palpation. His hands and feet are slightly erythematous and edematous and there is a maculopapular rash on the trunk. Which of the following is the most likely diagnosis?

684. You are seeing a 4-year-old girl with the physical examination finding shown below. She has no significant past history. The most appropriate management is which of the following?

685. At the 2-week checkup of a term female infant, the mother reports a grayish and sometimes bloody vaginal discharge since birth. The infant’s mother and grandmother are the only caretakers. Examination of the external genitalia reveals an intact hymen with a thin grayish mucous discharge. Which of the following is the most appropriate next step?

686. A 4196 g (9 lb 4 oz) infant is delivered via vaginal delivery to a 31-year-old mother with gestational diabetes. The delivery was complicated by shoulder dystocia. He is taken to the newborn nursery where his initial plasma glucose level is 20 mg/dL. The initial spun hematocrit is 65%. Which of the following congenital anomalies is this baby most likely to have?

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

688. A 4-year-old male is brought to the physician with fever and headache. His symptoms began two days ago with low-grade fever, cough, and congestion. Last night, he developed a temperature of 102 F (38.9 C) and became fussy and less active. Today, he is crying and complaining of a headache. His parents report that he has vomited twice today. In the office, his temperature is 102.5 F (39.o c), pulse is 110/min, and respiratory rate is 20/min. On examination, he is irritable and shows signs of photophobia. His oropharynx is erythematous. Nuchal rigidity is present and when the neck is flexed, the patient flexes his lower extremities. The remainder of the physical examination is normal. Lumbar puncture is performed and the results are shown below. CSF Glucose 60 mg/dL Protein 80 mg/dL RBC 10/mm3 WBC 100/mm3 Neutrophils 10% Lymphocytes 70% Monocytes 20% Gram stain negative Which of the following organisms is most likely responsible for this patient's presentation?

A 12-year-old boy is brought to the emergency department with a temperature of 39.1 C (102.4 F) at home, difficulty speaking, and odynophagia for 2 days, Physical examination reveals marked erythema of the right tonsil pillar and edema of the uvula with deviation to the left. In addition to anaerobic bacteria, which of the following organisms is most likely to be isolated from a tonsillar pillar aspirate?

690. A neonate is noted to have many abnormalities, a number of which are located in the midline. The infant has cleft lip and cleft palate. His eyes are very small and have fissures of the iris, shallow supraorbital ridges, and slanted palpebral fissures. He is deaf, and the ears are low set and malformed. Each hand has six fingers and a simian crease. Which of the following congenital abnormalities of the brain is particularly likely to be present in this infant?

691. A 4-year-old boy, recently adopted through an international adoption service, is noted to have intermittent watery diarrhea, nausea, belching, and abdominal pain. His weight is less than the fifth percentile for his age. Which of the following studies would be most helpful in making the diagnosis?

692. A 5-month-old child regularly regurgitates a large portion of her feeds. A pH probe study showed significant periods of low esophageal pH. The child has normal growth and no other significant past medical history. Which of the following is the best management at this point?

693. A 7 -year-old boy is brought to your office with a mild fever and neck swelling. His mother says that the boy has been complaining of neck pain for a couple of days and she noticed a tender neck lump yesterday. All of his vaccinations are up-to-date. He has no known allergies. Physical examination reveals a tender and fluctuant anterior cervical mass. Which of the following is the best medication for this patient?

694. A 21-year-old female, G1P0, who recently emigrated from Zimbabwe presents for prenatal counseling in her 34th week of pregnancy. She received no prenatal care. Ultrasound evaluation reveals lower-than-normal fetal length and markedly reduced fetal head size. Which of the following could have prevented this condition?

695. A 4-week-old infant presents with tachycardia, tachypnea, and poor weight gain. His arterial blood gas shows a pH of 7.34, a PaCO2 of 41 mm Hg, and a PaO2 of 74 mm Hg. A chest radiograph shows cardiomegaly. Echocardiography reveals a structurally normal heart, left ventricular dilatation, a left ventricular ejection fraction of 20%, and mild mitral and tricuspid regurgitation. IV administration of which of the following medications is the best initial step in management of this patient?

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

697. One of your asthmatic patients arrives for a checkup. The mother reports that the child seems to need albuterol daily, especially when exercising, and she has coughing fits that awaken her from sleep about twice a week. Her grandmother had recommended a Chihuahua as a “cure” for her asthma, but her mother has seen no difference since the arrival of the pet. Appropriate treatment measures would include which of the following?

698. An infant is brought to the office for health maintenance visit. On examination, the infant turns when her name is called. She is able to say "mama." Her mother mentions that she also says "dada" at home. She is able to look for her mother when she gets frightened. She also waves bye-bye to the doctor when the doctor steps out of the examination room. What age of this child is most consistent with these developmental milestones?

699. A 3-month-old infant is brought to the emergency department for severe vomiting over the past 6 hours. The mother tells the physician that she has vomited at least 4 times during this period. She also noticed the infant was having difficulty feeding for 2 days. On examination, she is very fussy, and there is a swelling over the left side of the head. CT of the head shows a skull fracture of the left parietal bone with no evidence of intracranial damage. The mother explains that the baby rolled off the sofa onto the floor yesterday. Which of the following is the most appropriate next step in management?

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