Pediatric USMLE 101 - 200

101. A child is brought to the physician for a routine visit. On examination, the child can name multiple items in the examination room, and can also combine 2 words into a short sentence. His mother estimates that he knows about 200 words. When his mother tries to help him onto the examination table, he says "me do it." Although his mother seems to understand most of what he says, you can only understand about half of his speech. Which of the following is the most likely age of this child?

102. A one-month-old child is brought to the office due to persistent vomiting for the last six days. His mother complains of increasing episodes of projectile vomiting. These episodes occur every time she attempts to feed him, and have persisted despite changing formulas. On physical examination, peristaltic waves are seen over the upper abdomen, and an olive-sized mass is palpated. Laboratory studies reveal a potassium level of 3 mEq/mL. What is the most appropriate management for this patient?

105. A 2-year-old girl is playing in the garage with her Chihuahua, only par- tially supervised by her father, who is weed-whacking around the garden gnomes in the front yard. He finds her in the garage, gagging and vomiting. She smells of gasoline. In a few minutes she stops vomiting, but later that day she develops cough, tachypnea, and subcostal retractions. She is brought to your emergency center. Which of the following is the most appropriate first step in management?

106. A 3-day-old girl has trouble feeding and pulmonary congestion. The mother says that the infant is so busy breathing, that she literally has no time to suckle. The girl was bom at home, with the delivery attended by a midwife. Physical examination confirms that she is in respiratory distress and shows bounding peripheral pulses with a loud continuous precordial machinerylike murmur. X-ray films show increased pulmonary vascular markings. Shortly thereafter, the infant goes into overt heart failure. Which of the following would most likely be required to correct this problem?

107. A 12-year-old girl presents with a 2-month history of vaginal discharge. She describes it as clear and states that it stains her underwear. She says that she hates boys, and that "no way" has she ever had sex or even kissed a boy. She reports having had developing breasts for 2 years and thinks that her growth spurt was about a year ago. Genital findings include a pubic hair stage of Tanner III with no evidence of redness or irritation of the vulvovaginal area. A slight amount of odorless, clear mucus is seen. Microscopic examination of the mucus reveals epithelial cells and a few bacteria, but no white cells. The pH is between 3.5 and 4. Which of the following is the most appropriate next step in management?

108. A 10-year-old girl is involved in a motor vehicle accident, sustaining multiple injuries to her head, arms, and abdomen. Her blood pressure is 90/60 mm Hg, and her pulse is 120/min. Her forearm is disfigured, and bone can be seen through the wound. She is breathing periodically and has cyanotic lips. Her abdomen is rigid, and there is flank discoloration. Which of the following is the most appropriate next step in management?

109. 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?

110. A 12-year-old boy is brought to the emergency department because of severe pain near his left knee. He has sickle cell disease and has been hospitalized previously for sickle cell crisis. Vital signs are notable for persistent fever. Examination of the left lower extremity reveals a normal knee joint with marked tenderness and swelling over the proximal tibia. Laboratory studies show leukocytosis and elevated ESR. Imaging studies confirm the diagnosis of osteomyelitis. Which of the following organisms is the most likely cause of his condition?

111. A 2-hour-old male neonate has developed worsening cyanosis over the past few minutes. The infant was vaginally delivered (assisted with forceps) at full term and weighed 4.1 kg (9 lb). The Apgar scores were 7 and 8 at 1 and 5 minutes, respectively. Oxygen is administered by mask but does not relieve the cyanosis. Further examination reveals tachypnea, subcostal retractions, a normal first heart sound, a single and loud second heart sound (S2), and no murmur. Which of the following is the most likely cause of the infant's cyanosis?

112. A 4-week-old infant is brought to the office due to several episodes of vomiting over the past week. The episodes have progressively become more frequent and forceful, but the vomitus never contains any blood or bile. The infant has been breastfed since birth. His vital signs are stable, and he is afebrile. An olive-shaped mass is palpated just to the right of the umbilicus, and peristaltic waves are seen in the upper abdomen. Lab studies reveal a sodium level of 135 mEq/L, potassium level of 3.3 mEq/L, chloride level of 92 mEq/L and bicarbonate level of 30 mEq/L. Which of the following is the most appropriate diagnostic test for this patient?

113. A one-year-old girl is brought to the office for the evaluation of sickle cell anemia. Both her parents have sickle cell trait, and her elder sister has sickle cell anemia. Her vital signs are stable. Her height and weight are appropriate for age. On examination, she appears healthy and normal. Her birth and past medical histories are insignificant. Hemoglobin electrophoresis reveals 40% hemoglobin S. What is the most common presentation of this condition?

114. A boy is brought to the office by his parents for a routine visit. During the physical examination, he can obey two-step commands, use two- to three-word phrases, and can build a tower of six blocks. According to his mother, he can walk up and down the stairs without help. What is the most likely age of this child?

115. A 5 year old girl presents to the emergency department with acute onset of muscle weakness. The mother carried the girl to the examination room and states that the muscle weakness started in her daughter's legs yesterday. The weakness became worse today and progressed to the trunk and both arms. She was also complaining difficulty of breathing earlier today. She has been otherwise healthy but had a common cold about 10 days ago. On examination, her respirations are 26/min and shallow. She has profound muscle weakness in her lower extremities, and moderate weakness in her upper extremities. Her deep tendon reflexes are absent. A lumbar puncture is performed, which shows increased protein concentration but no pleocytosis. Which of the following is the most likely diagnosis?

116. A full-term infant is brought to the office on her 6th day of life because her mother noted that she looked "yellow". The mother states that the infant is strictly breast-fed and has been eating every 2-3 hours. On examination, she is noted to be jaundiced over her trunk and face. There is no scleral icterus. She is otherwise healthy. Both the mother and baby are Rh positive. Which of the following is the most likely cause of this infant's jaundice?

117. A 4-year-old girl was diagnosed of left-side otitis media about 10 days ago and was prescribed oral amoxicillin, 40 mg/kg/day for 7 days. She has since developed bloody diarrhea with mucus, crampy abdominal pain, and fever. On physical examination, her temperature is 39.4 C (102.9 F), pulse is 88/min, and respirations are 16/min. She has normal bowel sounds and is diffusely tender to palpation. Which of the following is the most appropriate initial step in diagnosis?

118. A 5-year-old pedestrian is hit by a car in a mall parking lot and he is brought to the emergency department. There was loss of consciousness for less than 1 minute. On evaluation, the child has no neurologic deficits and a CT scan of the head reveals no intracranial abnormalities and no obvious skull fractures. The parents want to know what possible long-term problems there might be. You remember that problems after head trauma may include the development of seizures and that the risk of developing posttraumatic epilepsy is increased by which of the following?

119. A 4-year-old previously healthy but unimmunized boy presents with sudden onset of high fever, inspiratory stridor, and refusal to drink. Of the following causes of inspiratory stridor, which best fits this clinical scenario?

120. A week-old infant presents blood in his stools. He was born at home, with the father assisting in the delivery; no physician or midwife was present. He has been breast-fed and has been nursing well. On examination, you also note some blood in his nose. He is not jaundiced; a rectal examination and guaic test of the stool confirms that blood is present. His examination is otherwise normal. He is on no medications. Which of the following is the most likely diagnosis?

121. 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?

122. 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?

123. A 12-year-old American boy comes to you with the complaints of abdominal pain and dark urine. On examination he has normal vitals, icteric sclerae, and abdominal tenderness with a mass palpable in right upper quadrant. His laboratory report shows bilirubin: 6.5 mg/di, negative viral serologies and mild elevations of amylase and lipase. Ultrasonography shows a cystic extra hepatic mass and a gall bladder separated from the mass. What is the most likely diagnosis in this patient?

124. A 10-year-old boy has been having “bellyaches” for about 2 years. They occur at night as well as during the day. Occasionally, he vomits after the onset of pain. Occult blood has been found in his stool. His father also gets frequent, nonspecific stomachaches. Which of the following is the most likely diagnosis?

125. An 8-year-old boy presents to your office for a second opinion. He has a 2-year history of intermittent vomiting, dysphagia, and epigastric pain. His father reports he occasionally gets food “stuck” in his throat. He has been on a proton pump inhibitor for 18 months without symptom relief. His past history is significant only for eczema and a peanut allergy. Endoscopy was performed 6 months ago; no erosive lesions were noted and a biopsy was not performed. You arrange for a repeat endoscopy with biopsy. Microscopy on the biopsy sample reveals many eosinophils. Treatment of this condition should include which of the following?

126. A 4-year-old girl presents to the emergency department with fever and a petechial rash. A sepsis workup is performed, and IV antibiotics are administered. Gram-negative diplococci are identified in the CSF. Which of the following is true of this condition?

127. A 3-year-old boy suddenly begins choking and coughing while eating peanuts. On physical examination he is coughing frequently. He has inspiratory stridor and mild intercostal and suprasternal retractions. Initial management should include which of the following?

128. During a well-child visit, the grandmother of an 18-month-old patient is concerned because the child’s feet turn inward. She first noticed this when her grandson began to walk. It does not seem to bother the child. On examining his gait, his knees point forward and his feet turn inward. Which of the following is the most likely cause of this condition?

130. An infant can regard his parent’s face, follow to the midline, lift his head from the examining table, smile spontaneously, and respond to a bell. He does not yet regard his own hand, follow past the midline, nor lift his head to a 45° angle off the examining table. Which of the following is the most likely age of the infant?

131. A child is brought to your clinic for a routine examination. She can put on a T-shirt but requires a bit of help dressing otherwise. She can copy a circle well but has difficulty in copying a square. Her speech is understandable and she knows four colors. She balances proudly on each foot for 2 seconds but is unable to hold the stance for 5 seconds. Which of the following is the most likely age of this child?

133. A 1-month old boy is brought to the emergency department by his mother, who states that he has been having what she describes as "projectile vomiting" for the past several days. She states that he vomits every time she feeds him, and the situation seems to be getting worse, although he does not seem to be in pain. She describes the vomitus as non-bilious, and he has had normal stools with no blood in them. On examination, the infant appears to be mildly dehydrated, his abdomen is soft, and there is a palpable, olive-sized, firm moveable mass in the right upper quadrant. Which of the following is the most likely diagnosis?

134. A 3-month old infant is brought to a pediatrician's office because of increased lethargy and irritability. The parents state that the child rolled off the couch and fell on the floor one day prior to presentation. His parents report that the child has been previously healthy and is up to date on his vaccinations. He has been meeting his development milestones. His fontanelles are full. While in office the patient develops a tonic-clonic seizure. Which of the following is the next appropriate step?

135. A toddler is brought to the emergency department with burns on both of his buttocks. The areas are moist, have blisters, and are exquisitely painful to touch. The parents explain that the child accidentally pulled a pot of boiling water over himself. Which of the following is the most important step in management?

136. A pediatrician examines a 2-month-old infant who had been born at term. The pediatrician hears a continuous murmur at the upper left sternal border. The peripheral pulses in all extremities are full and show widened pulse pressure. Which of the following is the most likely diagnosis?

137. A 3-week-old infant is being evaluated for hema- : tochezia. His mother states that the infant passed stools j that contain both blood and mucus. There were no complications during her pregnancy, and the infant has been otherwise healthy. On physical examination, his temperature is 37.1 C (98.9 F), pulse is 110/min, and respirations are 18/min. He appears well, and his fontanelle is flat and level. Abdominal examination reveals normal active bowel sounds; his abdomen is nontender to palpation and there is no mass. His diaper contains stool that has bright red blood on it with mucus. Which of the following is the most likely explanation of his hematochezia?

138. A 7-year-old boy is brought to the physician because of a persistent mucopurulent nasal discharge for 2 weeks following a common cold. The mother also reports that the child has had frequent cough during the day and occasional temperatures up to 38.0 C (100.5 F). The child does not appear critically ill, but he complains of mild pain in the maxillary region and nasal obstruction. Rhinoscopic examination reveals a rivulet of purulent fluid coming from the inferior meatus. The rest of the physical examination is normal. Which of the following is the most likely diagnosis?

139. A9-year-old boy presents with a several-day history of progressive arm and leg weakness. He has been well except for an upper respiratory infection 2 weeks ago. The patient is alert and oriented. On repeated examination, the heart rate varies between 60 and 140 beats/min, and the blood pressure (BP) varies between 90/60 and 140/90 mmHg. Respirations are shallow, with a rate of 50/min. There is symmetric weakness of the face and all four extremities. Deep tendon reflexes are absent. Sensation is intact. Which of the following is the most likely diagnosis?

140. An 18-month-old boy is brought to the clinic for a checkup. As part of his routine care, a serum lead level is obtained. It is 25 g/mL. Which of the following is the most appropriate next step in his management?

141. An infant is due for her first dose of polio vaccine. Her parents have heard that there are two different types of vaccine for polio. They want to know why their daughter needs to get another shot rather than just taking the oral form of the vaccine. You tell the parents the major advantage of the injectable vaccine is which of the following?

143. A patient comes to your office for a hospital follow-up. You had sent him to the hospital 3 weeks earlier for persistent fevers but no other symptoms; he was diagnosed with endocarditis and is currently being treated appropriately. Advice to this family should now include which of the following?

144. A mother calls you on the telephone and says that your 4-year-old son bit the hand of her 2-year-old son 48 hours previously. The area around the injury has become red, indurated, and swollen, and he has a temperature of 39.4°C (103°F). Which of the following is the most appropriate response?

145. A 6-year-old boy is brought to the emergency department (ED) by the paramedics due to nausea, vomiting, diarrhea and abdominal pain over the past hour. His mother found an open multivitamin supplement bottle and some pills scattered on the kitchen floor. After his admission to the ED, he starts hyperventilating and experiences hematemesis. His blood pressure is 90/60 mmHg, pulse is 130/min, respirations are 50/min and temperature is 37.2 C (99F). Abdominal plain x-ray reveals several small opacities in the stomach and duodenum. Lab results are: Hb 13.5 g/dL Ht 42% WBC 10,000/cmm Platelets 300,000/cmm Blood Glucose 118 mg/dL Serum Na 135 mEq/L Serum K 34 mEq/L Chloride 102 mEq/L Bicarbonate 16 mEq/L BUN 16 mg/dL Serum Creatinine 1.0 mg/dL pH 7.30 P02 90 mm Hg PC02 29 mm Hg What is the most likely diagnosis?

146. A 3-year-old boy is brought to the office by his mother because he has been having painless passage of black stools for the past few days. Otherwise, his bowel habits are normal. He has no other medical problems. He takes no medication. His vital signs are within normal limits. The physical examination is unremarkable. What is the most likely diagnosis of this patient?

147. And photophobia. He has some difficulty in adapting to darkness. He is a very poor eater, and his diet consists mainly of canned foods, and very rarely, fresh vegetables or milk. Examination reveals dry, scaly skin, follicular hyperkeratosis in the extensor surfaces of the A 3-year-old boy is brought to the office by his parents for the evaluation of dry eyes extremities, and dry, silver-gray plaques on the bulbar conjunctiva. What is the most likely diagnosis of this patient?

148. A 2-week-old Caucasian male presents with constipation since birth. He was born full term via a normal vaginal delivery. He did not pass meconium till his 3rd day of life, after he was given a glycerin suppository. He has since stooled every 3–4 days, only with the help of a suppository. The stools are pellet like. He has had increasing abdominal distention. On rectal examination, tone appears normal and the ampulla contains no stool. Which of the following is the most likely cause?

149. Which of the following is the most appropriate evaluative procedure for an otherwise normal 7-day-old boy with perineal hypospadias?

150. A 44 year old woman delivers a 3120 g (6 lb 14 oz) newborn male. Her pregnancy was normal except that she noted decreased fetal movement compared to her previous pregnancies. She declined an amniocentesis offered by her obstetrician. Physical examination of the newborn reveals an infant with facial features suggestive of Down Syndrome. The infant then has bilious vomiting. An x-ray film showing the kidneys, ureters, and bladder (KUB) is performed, which shows a "double bubble" sign. Which of the following is the most likely cause of the abdominal signs and symptoms?

151. The parents of a 10-year-old girl with newly diagnosed, generalized tonic-clonic epilepsy come to the physician seeking advice regarding what they should do when the child has a seizure. Which of the following suggestions is appropriate?

152. A 10-year-old boy has a long history of recurrent infections. These have included pneumonia, suppurative lymphadenitis, persistent rhinitis, dermatitis, diarrhea, and perianal abscesses. Involved organisms have included Staphylococcus aureus, Serratia, Escherichia coli, and Pseudomonas. Biopsy of skin and lymph nodes have demonstrated granulomatous lesions, even though the only species isolated were those noted above. Immunoglobulin levels are higher than normal. Which of the following findings would be most helpful in establishing the diagnosis?

153. A 9-year-old Caucasian male complains of fever, sore throat and difficulty swallowing. Small tender lymph nodes are palpated in the cervical region. The symptoms subside quickly on penicillin therapy. Ten days later, the patient presents again with fever, skin rash and fleeting joint pain in the lower extremities. Physical examination reveals scattered urticaria and palpable lymph nodes in the cervical, axillary and inguinal regions. Which of the following is the most likely cause of this patient's current complaints?

154. 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?

156. A 10-year-old patient with sickle cell disease comes to the physician for a routine visit. The patient has a history of multiple pain crises and pneumonias. He was started on hydroxyurea one year ago and has not had any further pain crises since then. He has had no recent illnesses or hospitalizations. His physical examination is unremarkable. The patient's laboratory results are shown below. Complete blood count Hemoglobin 9.0 g/L Erythrocyte count 2.2 mln/mm3 MCHC 32% MCV 105 fl Reticulocytes 2.0% Platelets 212,000/mm3 Leukocyte count 9500/mm3 Neutrophils 56% Eosinophils 3% Lymphocytes 36% Monocytes 5% Which of the following best describes the role of hydroxyurea in the treatment of patients with sickle cell disease?

157. A 2-year-old child is brought to the physician for a routine visit. He is growing and developing appropriately. He eats a variety of foods including meat, vegetables, and fruits, and drinks 3-4 glasses of whole milk each day. He is starting to put words together into short sentences. His mother has no concerns. Physical examination is unremarkable. Routine laboratory studies show the following: Hemoglobin 9.5 g/dl RDW 14% MCV 65 fl Reticulocyte count 3.0% Platelet count 212,000/mm3 Leukocyte count 6,500/mm3 TIBC 300 mcg/dl (240-450 mcg/dl) Ferritin 1 00 ng/ml (7 -140 ng/ml) What is the most likely cause for this child's anemia?

158. A previously healthy 5-year-old girl is brought to the physician for evaluation of night awakenings. She has woken up screaming in each of the past three nights about one hour after going to sleep. When her parents go to her room, she is crying, sweating, and looks frightened. She does not respond to her parents and does not seem fully awake. When her parents hold her, she calms down and goes back to sleep. The next morning, she does not recall the incident. She started kindergarten this week and has just begun going all day without taking a nap. On examination, she is afebrile and her vital signs are within normal limits. A complete physical examination is unremarkable. What is the most likely diagnosis?

159. A 3-year-old boy is brought to the ER with a two-day history of decreased appetite, neck swelling, and irritability. He keeps his head rotated slightly to the right side. He resists passive flexion of the neck and rotation to the left side. Which of the following is the best next step in managing this patient?

160. A previously healthy 15-month-old girl is brought to the emergency department after she had several episodes in which she lost consciousness after crying. Her parents state that the episodes always occur when the child gets frustrated or upset. She has no cyanosis or incontinence. The episodes last about 45 seconds each. After the episode, she is alert and appropriate. Physical examination is unremarkable. What is the next best step in the management of this patient?

161. Apathient has the sudden onset of fretfulness and pain. He curls up with his legs drawn in to his abdomen. Over the next few hours he continued to have episodes of pain and cries with tears, but between these times he acts normally. The patient's mother fears something is terribly wrong and brings him to the hospital. His past medical history was unremarkable. The previous week he had had a cold with a runny nose. His stools had been normal that day. On examination he is quiet and his abdomen is surprisingly soft and normal. In the emergency room there is a semi-soft stool with some blood mixed with mucus. This classic presentation of intussusception is most likely to occur in which of the following age groups?

162. A 12-year-old boy is brought to the clinic because of a several-month history of strange behavior. According to his parents, the boy occasionally will start staring and not respond. He will also have tears in his eyes. These episodes last several seconds and he then returns to his baseline. He has not sustained any head trauma and is on no medications. Which of the following drugs is the most appropriate treatment?

163. A 9-month-old is brought to the emergency center by ambulance. The child had been having emesis and diarrhea with decreased urine output for several days, and the parents noted that she was hard to wake up this morning. Her weight is 9 kg, down from 11 kg the week prior at her 9-month checkup. You note her heart rate and blood pressure to be normal. She is lethargic, and her skin is noted to be “doughy.” After confirming that her respiratory status is stable, you send electrolytes, which you expect to be abnormal. You start an IV. Which of the following is the best solution for an initial IV bolus?

164. You are admitting to the hospital a 3-month-old infant who has been having poor feeding, emesis, and diarrhea for 3 days. In the emergency center, her electrolytes were found to be: sodium 157 mEq/L, potassium 2.6 mEq/L, chloride120 mEq/L, bicarbonate 14 mEq/L,creatinine1.8 mEq/L, blood urea nitrogen(BUN) 68 mEq/L, and glucose195 mEq/L. She was given a fluid bolus in the emergency center and has subsequently produced urine. Which of the following is the most appropriate next step in her management?

165. At exploratory laparotomy for blunt abdominal trauma, a 14-year-old boy is found to have a ruptured spleen. The spleen is shattered into multiple fragments, and there are other serious intraabdominal injuries that will require significant operative time. For the above reasons, it is decided that a quick splenectomy is indicated, and it is done. In the postoperative period, this young man should receive which of the following treatments?

166. A 10-year-old girl has bullous target lesions and mucosal erythema, which developed after her third dose of trimethoprim-sulfamethoxazole for a urinary tract infection. Which of the following is a likely associated clinical finding?

167. A 16-year-old boy is brought into the emergency department by his friends. He is semicomatose, with a pulse of 60/min and respirations of 6-8/min. His pupils are constricted. Which of the following will most likely be revealed on a urine toxicology screen?

168. A 6-month-old previously health child is brought to the doctor's office because of sudden onset of lethargy, constipation, generalized weakness and poor feeding. He has been meeting all development milestones and his immunization schedule is up to date. On further questioning, his parents mention that his diet was recently advanced to a homemade formula of evaporated milk and honey. On physical examination, he has stable vital signs, clear lungs, normal skin turgor and full fontanelles. Which of the following is the most likely explanation for the patient's presentation?

169. A 12-year-old girl was hit in the face by a baseball 15 minutes earlier and has had her mandibular incisors knocked out. Which of the following represents the best plan of action?

171. A 17-year-old boy comes to medical attention because of recurrent sinusitis and pneumonia, and persistent watery diarrhea due to Giardia lamblia. His parents and a sister are in excellent health. Physical examination reveals enlarged lymph nodes in cervical, axillary and inguinal regions. A lymph node biopsy shows hyperplastic follicles with an absence of plasma cells. Laboratory investigations show: Hematocrit.......................44% Leukocyte count...............9,800/mm3 Neutrophils.....................55% Lymphocytes..................30% Monocytes.....................5% CD4 T-cell count............1000 cells/mm3 Proteins, serum...............6.2 g/dL Albumin........................5.0 g/dL Globulin........................1.2 g/dL Additional studies demonstrate severely depressed levels of serum IgG, with slightly below- normal levels of IgM and IgA. Which of the following is the most likely diagnosis?

172. An 8-year-old boy presents with a 2-day history of rash. The rash started on the head and spread downward to his trunk and extremities. He also complains of a fever, cough, and a runny nose for the past 5 days. On physical examination, his temperature is 38.2 C (100.7 F), blood pressure is 88/56 mm Hg, pulse is 76/min, and respirations are 16/min. There is a small, irregular red spot with a central gray color on his buccal mucosa. The rash on his body is erythematous and maculopapular in quality. Which of the following is the most likely diagnosis?

173. A 4-week-old male infant has been spitting up his formula feedings for the past few days. He does not vomit bilious material or blood. The spitting up is gradually becoming more frequent, and forceful vomiting ensues. The vomitus seems to shoot straight out and nearly hit the wall. On examination, the baby seems hungry and is chewing his fist. His mucous membranes appear dry. A small, round mass, about the size of an adult thumbnail, is palpated in the upper abdomen. Laboratory data reveal Na+ of 133 mEq/L, K+ of 3.5 mEq/L, CI of 93 mEq/L, and HC0 3 - of 29 mEq/L. Which of the following is the most appropriate next step in management?

174. A 3-year-old child presents in clinic with marked erythema of the cheeks, with no prior symptoms. The rash soon involves the arms and has a reticular erythematous maculopapular appearance. The patient has been previously healthy and is not on any medications. He has not been exposed to any other ill individual. Which of the following is the most likely diagnosis?

175. The mother of a 6-month-old infant is concerned that her baby may be teething. You explain to her that the first teeth to erupt in most children are which of the following?

176. A male infant born at term is found to have bilateral colobomas, choanal atresia, ear anomalies, and cryptorchidism. There is no history maternal drug or alcohol abuse during pregnancy. There is no family history of similar congenital defects. Which of the following is the most appropriate initial test to exclude any associated abnormalities?

177. A 15-year-old girl presents to the emergency department with the sudden onset of watery diarrhea tinged with blood. The girl was previously healthy. Her only medications are topical benzoyl peroxide and oral clindamycin for acne vulgaris. Physical examination reveals a slightly distended abdomen that is diffusely tender. Her temperature is 38.1 C (100.5 F). She has not been exposed to any uncooked meat and has not eaten any unusual foods. Which of the following is the most likely diagnosis?

178. A 22-year-old woman has just delivered a male infant at 41 weeks of gestation. Her medical history is normal and her pregnancy was uncomplicated. She is an assistant in a veterinary clinic. Examination of the infant reveals jaundice, hepatosplenomegaly, and generalized lymphadenopathy. During the examination, he suddenly begins to have tonic- clonic seizures. The CT scan reveals active inflammatory lesions, hydrocephalus and intracranial calcifications. What is the most likely diagnosis of this patient?

179. A 5-year-old girl is brought to the physician's office for a follow-up visit after recovering from an episode of acute bacterial meningitis. Five weeks ago, she developed pneumococcal meningitis, and was admitted to the hospital, where she underwent lumbar puncture, CT scan of the head, and ceftriaxone therapy. She was discharged in a stable condition. According to the mother, the child has not been performing well in school since her illness. She also noticed that the child has forgotten how to copy figures such as triangles and squares, and is unable to identify colors accurately. What is the most likely cause for the regression of milestones in this patient?

181. The parents of a 2-month-old baby boy are concerned about his risk of coronary artery disease because of the recent death of his 40-year-old maternal uncle from a myocardial infarction. Which of the following is the most appropriate management in this situation?

182. An 8-month-old female infant is brought to the clinic for a well-baby examination. She was born prematurely at 35 weeks gestation. She weighs 2.3kg (5 Ib). She cannot sit unsupported. Physical examination reveals mild facial hypoplasia, epicanthal folds, micrognathia, long nasal philtrum, thin upper lip and short palpebral fissures. Auscultation of the heart reveals an III/ IV harsh holosystolic murmur over the precordium. Her karyotype is normal. What is the most likely cause of these findings?

183. A 12-year-old boy is brought to the clinic by his parents because "he cannot walk anymore." Yesterday, he became irritable, uneasy, and complained of tingling and weakness in both his legs. This morning, he couldn't stand up or move his legs, and complained of pain in his leg and thigh muscles. He denies any headaches, nausea or vomiting. He had an episode of febrile diarrhea 10 days ago. His family history is unremarkable. Physical examination reveals symmetric flaccid paralysis of both legs, absent deep tendon reflexes, and decreased superficial touch and vibratory sense. There is no nuchal rigidity. What structure is most likely affected in this patient's condition?

184. A 5-month-old infant is brought to the physician for a routine visit. The child was born full term without complications. The infant has been seen several times for poor weight gain. The infant takes 5 ounces of formula every 4 hours, and has been tried on increased calorie formula without success. Family history is significant only for nephrolithiasis. On examination, the infant's weight is <5%, height is at the 20% and head circumference is at the 20%. The infant appears thin, but the remainder of the physical examination is unremarkable. Screening labs are shown below. Chemistry panel Serum sodium 140 mEq/L Serum potassium 3.0 mEq/L Chloride 113 mEq/L Bicarbonate 15 mEq/L Blood urea nitrogen (BUN) 10 mg/dl Serum creatinine 0.5 mg/dl Calcium 9.0 mg/dl Blood glucose 98 mg/dl The urine pH is 7.9 and urinary sodium and potassium are within normal limits. What is the most likely cause for this patient's failure to thrive?

185. A 6-year-old boy has had a fever for 8 days. He just finished a 5-day course of amoxicillin for otitis media. On examination, his temperature is 38.6 C (101.4 F). He has meningismus and palsy of the left sixth cranial nerve. Cerebrospinal fluid (CSF) analysis reveals 200 white cells per mL with 80% lymphocytes and 20% polymorphonuclear leukocytes, glucose of 18 mg/dL, protein of 260 mg/dL, and a negative Gram stain. There is basilar enhancement without focal lesions on CT. Which of the following CSF tests will most likely identify the cause of meningitis?

186. A previously healthy 5-month-old boy has been irritable and has had a decreased oral intake for 2 days. His rectal temperature is 37.4 C (99.3 F), pulse is 220/min, and respirations are 50/min. The radial and posterior tibial pulses are diminished with good brachial and femoral pulses. ECG shows tachycardia; QRS complexes are narrow without preceding P waves. Which of the following is the most appropriate initial step in management?

187. A 5-year-old boy suffers from a condition characterized by recurrent fungal and viral infections, thymic hypoplasia, tetany, and abnormal facies. Serum levels of immunoglobulins are mildly depressed, and lymph node biopsy shows lymphocyte depletion of T-dependent areas. Which of the following is the underlying pathogenetic mechanism?

188. A 5-year-old boy is brought to the physician because of a malodorous discharge coming from his right nostril. His parents report that the child developed frequent sneezing and mucus discharge for one week. They thought it was a common cold. The child is afebrile and in apparent good health. There is no history of allergic diseases or recurrent infections. Examination reveals obstruction of the right nasal fossa with associated purulent discharge from the right nostril. Which of the following is the most likely diagnosis?

189. A 4-year-old girl is brought to your office by her mother for recent onset of fever and rash. For the past 4 days, she has had headaches, fever, and sore throat. She was apparently normal4 days ago, and upon presentation of the symptoms, her mother thought that she was having a simple viral fever which would go away with time; however, she then developed a pale pink maculo-papular rash, first on the face and neck, and then it rapidly spread onto the trunk and limbs. On examination, the child is afebrile and doesn't appear ill, but there are few palpable suboccipital and posterior auricular lymph nodes. What is the most likely cause of this patient's condition?

190. While working in the newborn nursery, you have the chance to counsel a first time mother. She had a healthy pregnancy and good prenatal care. The infant was delivered via normal spontaneous vaginal delivery and is doing well. You are counseling the mother on the benefits of breastfeeding, and she asks you what the differences are between human milk and formula. Which of the following is a true statement?

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

193. A newborn is diagnosed with congenital heart disease. You counsel the family that the incidence of heart disease in future children is which of the following?

194. A 5-year-old girl is brought to medical attention by her parents 12 hours after the onset of generalized tonicoclonic seizures. She never had similar episodes in the past. The girl is otherwise healthy. Her temperature is 37 C (98.6 F). Physical examination is unremarkable. There is no evidence that the girl had a fever at the onset of the convulsive episode. The parents fear that seizures may damage the child's brain and may eventually recur. Which of the following is the most appropriate next step in management?

195. An otherwise healthy 13-year-old boy has seasonal allergic rhinitis. He complains of excessive rhinorrhea, frequent sneezing, and nasal congestion. He has a nasal voice and breathes with his mouth. He derives some relief from keeping windows closed at home and spending as litde time as possible outdoors in periods of high pollen concentration. However, he is excessively bothered by nasal congestion. Which of the following drugs would be most effective in relieving nasal congestion?

196. During a regular checkup of an 8-year-old child, you note a loud first heart sound with a fixed and widely split second heart sound at the upper left sternal border that does not change with respirations. The patient is otherwise active and healthy. Which of the following heart lesions most likely explains these findings?

97. A 2-year-old child with minimal cyanosis has an S3 and S4 (a quadruple rhythm), a systolic murmur in the pulmonic area, and a middiastolic murmur along the lower left sternal border. An ECG shows right atrial hypertrophy and a ventricular block pattern in the right chest leads. Which of the following is the most likely diagnosis?

198. A woman brings her 3-year-old son to the emergency room after witnessing him swallow a disk-shaped battery. She adds that he vomited once on the way to the hospital. The vomitus was non-bloody and did not contain the battery. Physical examination of the child's chest is unremarkable. Plain radiographs reveal that the battery is located in the esophagus. What is the most appropriate next step in the management of this patient?

199. A 7 -year-old Caucasian boy is brought to the emergency room with a severe headache, vomiting, and altered mental status of acute onset. His temperature is 36.7 C (98 F), blood pressure is 130/70 mm Hg, pulse is 60/min, and respirations are 18/min. Neurologic examination reveals nuchal rigidity, but no focal neurologic signs. A CT scan shows blood in the subarachnoid space. Which of the following is the most probable additional finding in this patient?

200. A 28-month-old female has been living with her mother in a shelter for homeless women and children. She is brought to the Emergency Department in status epilepticus, which is stopped with intravenous lorazepam. She is placed on a cardiac monitor and a wide complex tachycardia is noted. The ventricular tachycardia reverts to sinus tachycardia after defibrillation is performed. Her temperature is 38.5 C (101.3 F), blood pressure is 120/80 mm Hg, pulse is 195, and respirations are 26. Physical examination reveals a lethargic, pale toddler with dilated and reactive pupils, dry mucous membranes, shallow respirations, diaphoresis and brisk deep tendon reflexes. A urine toxicology screen is most likely to detect which of the following substances?