Basic Usmle

14) A 10-year-old boy comes to the office with fever and chills for 5 days and myalgia. He has recently returned from a 2-week vacation to New England with his family. On physical examination he has mild splenomegaly. Which of the following is the most likely cause of his symptoms?

23) 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?

30) 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?

32) A 12-year-old girl is brought to the clinic due to a 2-month history of headaches. Her headaches last 1-2 hours and have no fixed time of occurrence. She denies nausea, vomiting, chills or fevers. She has no other medical problems and takes no medication. Her family history is significant for hypertension and diabetes. Her blood pressure is 156/90 mm Hg, pulse is 80/min, and respirations are 14/min. Examination shows an alert child in no distress. There is a soft to-and-fro bruit heard at the right costovertebral angle. Which of the following is the most likely cause of her hypertension?

43) A 15-year-old Ashkenazi Jewish boy comes to the office because of pain in his right knee. He gives a history of easy bruising and chronic fatigue. His height and weight are in the 40th percentile mark for his age. The physical examination reveals tenderness over the lower end of the right femur, mildly enlarged liver, and moderately enlarged spleen. X-rays of the right femur reveal an Erlenmeyer flask deformity of the distal femur. Significant lab findings are anemia and thrombocytopenia. A bone marrow examination reveals cells with a wrinkled paper appearance. What is the most likely cause of this patient's condition?

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

90) A 2-week-old infant presents with hepatosplenomegaly and a thick, purulent, bloody nasal discharge. Coppery, oval, maculopapular skin lesions are present in an acral distribution. The neurologic examination is normal, including head circumference. Which of the following is the most likely cause of this congenital infection?

102) A 2-year-old girl is brought to the clinic due to fever, irritability and lethargy for the past two weeks. Over the past two months, she has complained of intermittent abdominal discomfort and has lost weight. Abdominal palpation reveals a firm nodular mass in the right flank. No bruits are heard. Abdominal x-ray reveals multiple calcifications in the renal area. Urine examination reveals increased levels of homovanillic acid and vanillylmandelic acid. Which embryonic structure has this mass most likely arisen from?

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

122) A 22-year-old college student went to the health clinic complaining of a fever over the last 5 days, fatigue, myalgias, and a bout of vomiting and diarrhea. The clinic doctor diagnosed him with acute gastroenteritis and told him to drink more fluids. Three days later, the student presents to the ED complaining of substernal chest pain that is constant. He also feels short of breath. His temperature is 100.9°F, HR is 119 beats per minute, BP is 120/75 mmHg, and RR is 18 breaths per minute. An ECG is performed revealing sinus tachycardia. A chest radiograph is unremarkable. Laboratory tests are normal except for slightly elevated WBCs. Which of the following is the most common cause of this patient’s diagnosis?

123) A 22-year-old female is hospitalized after a car accident. She sustained a hip fracture, fractures of several ribs and a blunt abdominal injury that required a laparotomy. The laparotomy revealed a liver laceration and extensive hemoperitoneum. In the early postoperative period, the patient is noted to have hyperactive deep tendon reflexes. Which of the following electrolyte abnormalities may be responsible for this condition?

141) A 23-year-old woman presents to the ED complaining of pain with urination. She has no other complaints. Her symptoms started 3 week ago. During this time, she has been to the clinic twice, with negative urine cultures each time. Her condition has not improved with antibiotic therapy with sulfonamides or quinolones. Physical examination is normal. Wet mount showed epithelial cells. Which of the following organisms is most likely responsible for the patient’s symptoms?

218) A 3-month-old Jewish infant is brought to the emergency department because of a generalized seizure 1 hour ago. He is lethargic, weighs 2.7kg (61b), and has a doll-like face with fat cheeks, relatively thin extremities, and a protuberant abdomen. His liver is felt 5cm (2in) below the right costal margin. His kidneys are enlarged. His blood sugar level is 40mg/dl. His serum uric acid, total cholesterol, triglycerides and lactic acid levels are elevated. The levels of his liver transaminases are normal. What is the most likely cause of this infant's symptoms?

247) A 32-year-old Caucasian male presents to the ER with a 12-hour history of anorexia and vomiting. He says that he feels “a little dizzy”. He denies abdominal pain or diarrhea. His past medical history is insignificant His blood pressure is 110/70 mmHg while supine and 100/60 mmHg while sitting. His heart rate is 90/min. His laboratory values are: Serum sodium 139 mEq/L, Serum potassium 3.1 mEq/L, Serum calcium 8.9 mEq/L, Serum chloride 88 mEq/L, Serum bicarbonate 33 mEq/L, Blood glucose 95 mg/dl, BUN 20 mg/dl, Serum creatinine 1.1 mg/dl. Which of the following is the most likely cause of the decreased chloride level in this patient?

251) A 32-year-old male complains of progressive weakness and exertional dyspnea. His past medical history is significant for a knife injury to the right thigh two months ago. He has been arrested several times for robbery. He consumes alcohol regularly, and smokes crack occasionally. His younger brother died of cystic fibrosis. His blood pressure is 160/60 mmHg, and heart rate is 100/min. His extremities are warm and flushed. Carotid upstroke is brisk. The point of maximal impulse is displaced to the left, and a soft, holosystolic murmur is heard over the cardiac apex. The murmur does not change with the Valsalva maneuver. Which of the following is the most likely cause of this patient's symptoms?

255) A 32-year-old man is brought to the emergency department by paramedics after being found wandering downtown, apparently delirious and agitated. During transport to the hospital the patient becomes diaphoretic and tremulous and has a blood pressure to 163/100 mmHg, pulse of 102/min, and temperature of 39°C (102.2°F). On examination the patient has dilated pupils and ulcerations of his nasal septum mucosa with the residue of a white powder along the nasal alae in addition to his tachycardia, hypertension, hyperthermia, and agitation. Which of the following is the reason why nonselective β-blockers should be avoided in this patient?

302) A 38-year-old female comes to your office complaining of occasional palpitations. She describes feeling a fast and irregular heartbeat. Over the past two months, she has had three such episodes, each lasting about two hours. She denies any associated chest pain, shortness of breath cough or ankle swelling. She drinks alcohol on social occasions and does not smoke cigarettes. She has no other medical problems and is not taking any medications. On physical examination, her temperature is 37.1°C (98.9°F), pulse is 80/min, blood pressure is 130/70mmHg, and respirations are 14/min. On auscultation of her heat the apical impulse is displaced and there is an S3. You also hear a pansystolic murmur, which is loudest at the apex and radiates to the axilla. Which of the following is the most likely cause of her symptoms?

304) A 38-year-old G4P3 at 33 weeks gestation is noted to have a fundal height of 29 cm on routine obstetrical visit. An ultrasound is performed by the maternal-fetal medicine specialist. The estimated fetal weight is determined to be in the fifth percentile for the estimated gestational age. The biparietal diameter and abdominal circumference are concordant in size. Which of the following is associated with symmetric growth restriction?

322) A 4-year-old child presents in the clinic with an illness notable for swelling in front of and in back of the ear on the affected side, as well as altered taste sensation. Correct statements about this condition include which of the following?

335) A 42-year-old morbidly obese man is being evaluated for poor sleep. He complains of frequent awakenings due to a choking sensation and says that the resulting tiredness severely limits his physical activity. He also complains of chronic leg swelling. He denies cigarette, alcohol, or drug use. On physical examination, his blood pressure is 160/100 mmHg and his heart rate is 110/min. Which of the following additional findings is most likely to be present in this patient?

343) A 43-year-old man presents to your office with low energy and increased fatigability. He also complains of daytime sleepiness and occasional headaches. He drinks two to three glasses of wine daily but does not smoke. He sleeps in a separate room from his wife because she finds his constant snoring annoying. On physical examination, his blood pressure is 160/100 mmHg and his heart rate is 80/min. His BMI is 31.5 kg/m2. His abdomen is soft and non-tender. The liver span is 10 cm and the spleen is not palpable. Laboratory findings are: Hematocrit 60%, WBC count 9,000/mm3, Platelets 190,000/mm3. Which of the following is most likely responsible for this patient's increased hematocrit?

345) A 43-year-old trauma patient develops acute respiratory distress syndrome (ARDS) and has difficulty oxygenating despite increased concentrations of inspired O2. After the positive end-expiratory pressure (PEEP) is increased, the patient’s oxygenation improves. What is the mechanism by which this occurs?

353) A 45-year-old Asian man presents to your office complaining of easy fatigability. He denies abdominal pain, distention, nausea, vomiting, or significant weight loss. His past medical history includes a gastrectomy for a non-healing gastric ulcer. He is not currently taking any medications. He quit smoking several years ago and does not use alcohol or illicit drugs. His vital signs are within normal limits. Physical examination reveals a shiny tongue and pale palmar creases. No lymphadenopathy, hepatomegaly, or splenomegaly is present. His blood hemoglobin level is 7.5 mg/dL and W8C count is 3,800/mm3. Stool tests for occult blood are repeatedly negative. This patient's condition involves which of the following pathophysiologic mechanisms?

365) A 45-year-old woman is seen with wasting of the intrinsic muscles of the hand, weakness, and pain in the wrist. Which of the following nerves has most likely been injured?

369) A 46-year -old alcoholic man comes to the emergency department because of several episodes of vomiting. The last episode of emesis contained blood. Five hours ago, he had a fatty meal and several alcoholic drinks. Two days ago, he had an upper GI tract endoscopy and abdominal ultrasound for the evaluation of dyspepsia. The endoscopy was unremarkable, and the ultrasound showed a hyperechogenic enlarged liver and stones in the gallbladder. His temperature is 36.6°C (97.9°F), blood pressure is 120/70 mm Hg, pulse is 95/min, and respirations are 15/min. Laboratory studies show: Hb 12.8 g/dl, WBC 5,400/cmm, BUN 26 mg/dl, Creatinine 1.1 mg/dl, AST 100 U/L, ALT 45 U/L, Bilirubin 0.7 mg/dl. Nasogastric suction shows normal stomach contents mixed with bright red blood. The rectal examination shows no melena. Which of the following is the most likely explanation for this patient's bloody vomiting?

380) A 47-year-old man presents to your office complaining of occasional daytime headaches, dizziness and nausea. He has no significant past medical history. He works as a traffic controller in an underground parking lot. He does not smoke cigarettes, and consumes alcohol only on weekends. He is sexually active in a monogamous relationship with his wife and uses condoms for contraception. His cardiac exam is unremarkable. His abdomen is soft and non-tender. The liver span is 8 cm and the spleen is not palpable. Laboratory findings are: Hematocrit 59%, WBC count 7,000/mm3, Platelets 200,000/mm3. Which of the following is most likely responsible for this patient's increased hematocrit?

184) A 27-year-old man presents to the emergency department with unremitting nose bleeding. He reports having a similar bleeding episode one year ago that was stopped in the ER. He works as a computer programmer and has a sedentary lifestyle. He drinks alcohol on social occasions but does not smoke or use illicit substances. On physical examination, there are several ruby-colored papules on his lips that blanch partially with pressure. Digital clubbing is also present. His abdomen is soft and non-tender. The liver span is 8 cm and the spleen is not palpable. Laboratory findings are: Hematocrit 60%, WBC count 8,000/mm3, Platelets 180,000/mm3. Which of the following is most likely responsible for this patient's increased hematocrit?

402) A 51-year-old woman comes to your office for a routine health maintenance examination. She has no medical history but states that she has been having irregular menses and occasional hot flashes for the past eight months. Her husband has told her that she appears moody all the time. She has not had any surgeries in the past and currently takes no medications. She has a very stressful job and drinks two to three cups of coffee every morning. She does not smoke, but she does drink four to five twelve-ounce beers a day for the past 20 years to relieve her stress. She is a lacto-ovo vegetarian and walks two miles on a treadmill each day. Her temperature is 36.5C (97.7F), blood pressure is 120/70, heart rate is 84 beats/minute, and respirations are 12/minute. She is 5'4" and weighs 180 pounds (BMI is 30.9 kg/m2). Physical examination is unremarkable. You inform her that she is probably reaching menopause, and that she will be at an increased risk of developing osteoporosis. Which of the following is the most significant risk factor for the development of osteoporosis in this patient?

439) A 56-year-old male presents with progressively worsening dyspnea over a 4 month period. He denies fever, chest pain, cough or ankle swelling and does not use tobacco, alcohol or drugs. He works for a home insulation and plumbing company. He has never been abroad and does not own any pets. His only medications are hydrochlorothiazide and metoprolol for blood pressure control. On physical examination, his temperature is 36.8°C (98.2°F), pulse is 76/min, blood pressure is 130/78 mmHg, and respirations are 15/min. Examination shows digital clubbing and fine bibasilar end-inspiratory crackles. Jugular venous pressure is 7 cm and there is no peripheral edema. Which of the following additional findings is most likely in this patient?

470) A 6-year-old Caucasian boy is hospitalized for acute sinusitis that was accompanied with intensive nasal bleeding. Past medical history is significant for recurrent pulmonary infections and several hospitalizations for parenteral antibiotic therapy. The sweat chloride test is positive. The blood tests reveal a prothrombin time (PT) of 20 seconds. Which of the following coagulation factors is most likely to be deficient in this patient?

484) A 60-year-old man with no past medical history undergoes upper endoscopy and biopsy for an upset stomach that is worsened by eating. He is found to have inflammation predominantly in the antrum of the stomach. Which of the following is the most likely etiology of this condition?

504) A 63-year-old woman with a long history of hypertension faints after experiencing the sudden onset of severe chest pain that radiates to her back. She is rushed to the emergency room. Upon arrival she is agitated and demands quick pain relief. Her heart rate is 110/min and blood pressure is 90/50 mmHg. Jugular veins are distended. An intra-arterial catheter shows significant variation of systolic blood pressure related to the respiratory cycle. Chest x-ray reveals widening of the mediastinum. Which of the following is the most likely cause of this patient's syncope?

522) A 65-year-old man complains of lower leg swelling, fatigue and poor appetite. His past medical history is significant for recurrent chest infections, wheezing, cough, recent pyelonephritis, and arterial hypertension. He smokes 1 pack of cigarettes a day but denies alcohol or intravenous drug use. His physical examination reveals a barrel-shaped chest with bilateral scattered wheezes. His abdomen is distended and his liver edge is palpated 4 cm below the right costal margin. You note pitting edema and dilated, tortuous, superficial veins over the bilateral lower extremities. Manual pressure on the abdomen causes persistent distention of the jugular veins. The patient's serum sodium level is 135 mEq/L and his creatinine concentration is 1.2 mg/dl. An abnormality of which of the following is most likely to explain his edema?

534) A 66-year-old retired carpenter presents with chronic shortness of breath upon exertion. He has smoked one pack of cigarettes per day for the past 5 years and drinks alcohol regularly. Physical examination reveals a displaced point of maximal impulse and hepatosplenomegaly. His medications include pantoprazole for gastroesophageal reflux and sertraline for depression. Echocardiogram reveals an ejection fraction of 30% and dilated left and right ventricles. Laboratory tests show: Na+: 129 mEq/L, K+: 5.2 mEq/L, Cl−: 101 mEq/L, Blood urea nitrogen: 45 mg/dL, Creatinine: 1.3 mg/dL, Glucose: 134 mg/dL, Aspartate aminotransferase: 220 U/L, Alanine aminotransferase: 140 U/L, Alkaline phosphatase: 280 U/L. Which of the following is the most likely cause of his cardiac findings?

540) A 67-year-old man presents to his primary care provider in January with fever and a productive cough. The patient had been seen ten days earlier with complaints of fever to 102°F (39.0°C), myalgias, rhinorrhea, and dry cough. At that time, his lung exam revealed occasional crackles. He was given a medication and told to follow up if his symptoms worsened. The symptoms did remit over the first five days, but he began to feel worse again two days ago. He smokes a half-pack of cigarettes per day and drinks alcohol several times a week. On exam today, his temperature is 102.3°F (39.3°C), and lung exam reveals increased tactile fremitus in the left lower lobe. What is the most likely pathogen responsible for his current condition?

553) A 7-year-old boy presents with tenderness and erythema of one knee joint. He has had troubles with infections since about 3 months of age. A brother and a maternal uncle both died of infectious disease at an early age. A detailed immunologic evaluation performed at 2 years of age demonstrated plasma IgG less than 50 mg/100 mL. Normal numbers of circulating T cells and normal cellular immunity were found. The boy had been treated monthly since then with IV immunoglobulin. This therapy had markedly reduced, but not eliminated, the boy's infection rate. Which of the following is the most likely pathogen to cause infectious arthritis in this patient?

564) A 72-year-old woman had a pacemaker inserted 4 years ago for symptomatic bradycardia because of AV nodal disease. She is clinically feeling well and her ECG shows normal sinus rhythm at a rate of 68/min but no pacemaker spikes. Her pacemaker only functions when the ventricular rate falls below a pre-set interval. Which of the following best describes her pacemaker function?

576) A 74-year-old nursing home resident is brought to the ER with a low-grade fever, cough and shortness of breath for the last two days. The cough is productive of small amounts of greenish sputum. His past medical history is significant for hypertension, diabetes mellitus type 2, COPD, hypercholesterolemia and mild dementia. His blood pressure is 152/78 mmHg and his heart rate is 89/min, regular. Physical examination reveals decreased breath sounds, coarse rhonchi, and increased fremitus over the lower left lung field. His oxygen saturation is 92% on room air when lying on his right side but drops to 84% when he lies on his left. Which of the following best explains this finding?

601) 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?

631) A patient was induced for being postterm at 42,5 weeks. Immediately following the delivery, you examine the baby with the pediatricians and note the following on physical examination: a small amount of cartilage in the earlobe, occasional creases over the anterior two-thirds of the soles of the feet, 4-mm breast nodule diameter, fine and fuzzy scalp hair, and a scrotum with some but not extensive rugae. Based on this physical examination, what is the approximate gestational age of this male infant?

619) A newborn has a midline defect in the anterior abdominal wall. The parents ask what, if anything, should be done. Spontaneous closure of which of the following congenital abnormalities of the abdominal wall generally occurs by the age of 4?

624) A one-month-old infant is brought to the physician for evaluation. His mother reports that for the past two weeks, he has been crying inconsolably for several hours every evening. His mother has tried multiple methods to calm the infant down, but nothing seems to work. The infant was born full term without complications. He takes two ounces of cow's milk-based formula every two hours and is growing well. His mother reports that he is happy and alert the rest of the day. The child's physical examination is unremarkable. Which of the following is a true statement about the child's condition?

664) 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?

676) An 8-year-old immigrant from rural Central America presents with complaints of weakness, facial swelling, muscle pain, and fever. A CBC reveals marked eosinophilia. Which of the following parasites is most likely to be responsible?

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

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?

685) 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?

689) An infant is born to a woman who has received very little prenatal care. The mother is anxious, complains of heat intolerance and fatigue, and reports that she has not gained much weight despite having an increased appetite. On examination the mother is tachycardic, has a tremor, and has fullness in her neck and in her eyes. The infant is most likely at risk for development of which of the following?

712) Otitis media occurring during the first 8 weeks of life deserves special consideration, because the bacteria responsible for infections during this time may be different from those that affect older infants and children. Which of the following organisms is the most likely to cause otitis media in these infants?

732) While playing with his children, a 44-year-old man falls and lands on his right shoulder. There is immediate pain and deformity. In an uncomplicated dislocation of the glenohumeral joint, the humeral head usually dislocates primarily in which of the following directions?

350) A 44-year-old woman presents with increased shortness of breath, cough, and sputum production. She has had asthma since childhood and uses her medications as directed. Recently, she noticed that her peak flow readings were decreasing after the symptoms started. On examination, she is in moderate respiratory distress, respirations 25/min, there are bilateral wheezes and oxygen saturation is 90% on room air. On her blood gas, the PCO2 is 50 mm Hg. Which of the following is the most likely mechanism for her carbon dioxide retention?

434) A 55-year-old woman is in the intensive care unit on a ventilator for hypoxemia following “flash” pulmonary edema. Her PO2 on the blood gas prior to intubation was 44 mm Hg, and now while breathing 100% oxygen on the ventilator her repeat blood gas reveals a PO2 of 80 mm Hg. Hypoxemia while receiving 100% oxygen indicates which of the following problems?

7. A 1-year-old boy is brought to the physician by his parents for evaluation of bruising and blood in his stool. The child has had multiple episodes of otitis media and has been hospitalized twice with pneumonia, but has never had bleeding or easy bruising in the past. He has been eating and drinking well with no vomiting or diarrhea. He is afebrile with a heart rate of 150/min and a blood pressure of 80/40 mmHg. On examination, he is well-developed, well-nourished, and has a fair complexion. There are dry, scaly patches on his cheeks and lower extremities. He also has bruising and purpura on his lower extremities. His diaper contains a small amount of occult blood positive stool, but no fissures are seen on rectal examination. The remainder of the physical examination is unremarkable. Laboratory studies show: Complete blood count Hemoglobin 11 .5 g/dL Platelet count 20,000/mm3 Leukocyte count 6,500/mm3 Neutrophils 76% Eosinophils 1% Lymphocytes 13% Monocytes 10% A peripheral smear reveals a low number of platelets, and the platelets that are seen are small. Which of the following is the most likely cause of his bleeding?

911. A 7-year-old girl is brought to the office by her mother. The mother is worried because she noticed some axillary hair development in her daughter. The girl appears calm, and denies the presence of headaches, visual disturbances or abdominal pain. There has been no change in her behavior. Her medical history is unremarkable. Her older sister's pubertal changes began at age 11. Physical examination reveals scarce and dark axillary hair, absent breast development and absent pubic hair. The rest of the examination is unremarkable. Activation of which of the following structures is most likely responsible for this patient's symptomatology?

295. A 2-year-old boy is brought to the office by his parents due to severe diarrhea since yesterday. He has had approximately 20 episodes of non-bloody, non-mucoid stool passage in the last twenty hours, and one episode of bilious vomiting. He is also feeding less than usual. He is febrile, tachycardic and moderately dehydrated. What is the most likely cause of his presentation?

560. 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?

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

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?

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

A child can walk well holding on to furniture but is slightly wobbly when walking alone. She uses a neat pincer grasp to pick up a pellet, and she can release a cube into a cup after it has been demonstrated to her. She tries to build a tower of two cubes with variable success. She is most likely at which of the following age?

A 12-year-old, previously healthy girl presents to her physician with a chief complaint of early morning headaches. She states that these headaches wake her up from sleep 2-3 days a week. She also complains of some vomiting associated with the headaches. The headaches have been getting progressively worse for the past 2 months. She denies any photophobia, dizziness, or blurred vision. There is no history of a recent respiratory infection, runny nose, or cough. There is no history of recent trauma. In the office, her vital signs are within normal limits. Her examination shows pupils that are equal, round, and reactive, with no maxillary or frontal sinus tenderness. Her tympanic membranes are clear and intact. Her neck is supple with full range of motion. Neurologic examination shows a positive Romberg sign. Which of the following tests would most likely confirm the diagnosis?

A 4-year-old child manifests symptoms of fever, sore throat, and swollen lymph nodes. The spleen tip is palpable. Throat culture and rapid slide (Monospot) test results are negative. The next logical diagnostic procedure would involve which of the following?

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

314. A father brings his 3-year-old daughter to the emergency center after noting her to be pale and tired and with a subjective fever for several days. Her past history is significant for an upper respiratory infection 4 weeks prior, but she had been otherwise healthy. The father denies emesis or diarrhea, but does report his daughter has had leg pain over the previous week, waking her from sleep. He also reports that she has been bleeding from her gums after brushing her teeth. Examination reveals a listless pale child. She has diffuse lymphadenopathy with splenomegaly but no hepatomegaly. She has a few petechiae scattered across her face and abdomen and is mildly tender over her shins, but does not have associated erythema or joint swelling. A CBC reveals a leukocyte count of 8,000/L with a hemoglobin of 4 g/dL and a platelet count of 7,000/L. The automated differential reports an elevated number of atypical lymphocytes. Which of the following diagnostic studies is the most appropriate next step in the management of this child?

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?

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?

1286) A 9-month-old, chubby, healthy-appearing boy is brought to the pediatrician because of episodes of colicky abdominal pain and blood-tinged stools. The pain lasts from 1 to 10 minutes and causes the infant to double up; he then appears normal until his next bout of colic. During the examination, the infant has another episode, at which time a vague mass can be felt on the right side of the abdomen, and the right lower quadrant has an "empty" feeling to deep palpation. Which of the following is the most appropriate initial step in management?

756. An otherwise healthy 17-year-old complains of swollen glands in his neck and groin for the past 6 months and an increasing cough over the previous 2 weeks. He also reports some fevers, especially at night, and possibly some weight loss. On examination, you notice that he has nontender cervical, supraclavicular, axillary, and inguinal nodes, no hepatosplenomegaly, and otherwise looks to be fairly healthy. Which of the following would be the appropriate next step?

962. A 4-year-old child is observed to hold his eyelids open with his fingers and to close one eye periodically, especially in the evening. He has some trouble swallowing his food. He usually appears sad, although he laughs often enough. He can throw a ball, and he runs well. Which of the following is most likely to aid in the diagnosis?

170. A patient presents in labor at term. Clinical pelvimetry is performed. She has an oval-shaped pelvis with the anteroposterior diameter at the pelvic inlet greater than the transverse diameter. The baby is occiput posterior. The patient most likely has what kind of pelvis?

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

695. A 30-year-old class D diabetic is concerned about pregnancy. She can be assured that which of the following risks is the same for her as for the general population?

3. After delivery of a term infant with Apgar scores of 2 at 1 minute and 7 at 5 minutes, you ask that umbilical cord blood be collected for pH. The umbilical arteries carry which of the following?

A 72-year-old woman complains of fatigue, dyspepsia, and short ness of breath. Her daughter tells you that her mother also has some slight memory loss and occasionally complains of numbness in her legs. The laboratory tests you ordered show a hemoglobin of 10.2 g/dl and an MCV of 110. The most likely cause is:

6. A 23-year-old male comes to ER with five-day history of diarrhea and abdominal pain. Initially, the diarrhea was watery occurring five-six times per day but yesterday he noticed blood in the stool which prompted his visit to ER. He describes his abdominal pain as colicky and severe. He also complains of nausea and decreased appetite but he has had no vomiting. His past medical history is insignificant and never had similar symptoms. He is not sexually active and he denies any illicit drug use. He has no history of recent travel. His father had colon cancer and his uncle died of liver cirrhosis. His temperature is 36.6C (98.0F), blood pressure is 123/82 mmHg and heart rate is 102/min. On examination, he has prominent periumbilical and right lower quadrant tenderness but no guarding or rebound. Rectal examination reveals brownish stool mixed with blood. Which of the following is the most likely diagnosis?

56. A 60-year-old man is brought to the ER by his wife because he lost consciousness in the bathroom at night. He says that he woke up, went to the bathroom to urinate, and fainted there. He rapidly recovered his consciousness without any indication of disorientation. He has never had such an episode before. He admits' problems with urination,' including difficulty with initiating urination and frequent awakening to void at night. He does not take any medication. His past medical history is insignificant. He smokes 2 packs of cigarettes per day and does not consume alcohol. His blood pressure is 130/80 mm Hg while supine, and 132/80 while standing. His heart rate is 70/min. His physical examination is within normal limits. The ECG is normal. What is the most probable cause of the syncopal episode in this patient?

27. A 64-year-old man complains of palpitations and progressive shortness of breath over the past several hours. He says that he also develops a choking sensation every time he tries to lie down. His medical history is significant for hypertension for the past 20 years and medication non-compliance. He also has a 35-year smoking history. He reports that his father died of a heart attack at age 70 and his mother suffered from asthma. On physical examination, his blood pressure is 170/100 mmHg and his heat rate is 130/min and irregularly irregular. Lung exam reveals bibasilar crackles. There is 2+ pitting edema of the lower extremities. Bedside echocardiography shows a left ventricular ejection fraction of 55%. Which of the following is most likely responsible for his symptoms?

202. A 55-year-old man presents to the ED with chest pain and shortness of breath. His BP is 170/80 mm Hg, HR is 89 beats per minute, and oxygen saturation is 90% on room air. Physical examination reveals crackles midway up both lung fields and a new holosystolic murmur that is loudest at the apex and radiates to the left axilla. ECG reveals ST elevations in the inferior leads. Chest radiograph shows pulmonary edema with a normalsized cardiac silhouette. Which of the following is the most likely cause of the cardiac murmur?

123. A 27-year-old woman presents to the emergency room with a panic attack. She appears healthy except for tachycardia and a respiratory rate of 30. Electrolytes include calcium 10.0 mg/dL, albumin 4.0 g/dL, phosphorus 0.8 mg/dL, and magnesium 1.5 mEq/L. Arterial blood gases include pH of 7.56, P CO2 21 mm Hg, and PO2 99 mm Hg. Which of the following is the most likely cause of the hypophosphatemia?

30. A 59-year-old man comes to the physician because of dysuria, urinary urgency, and frequency. He also complains of hematuria, nocturia, decreased force of stream, and a feeling of incomplete voiding. These symptoms have been present for more than a month. For the past few days he has been experiencing dull, non-radiating suprapubic pain. He has also been having low-grade fever and malaise for the past couple of days. He has been taking analgesics for osteoarthritis of his right knee for more than 10 years. He has a 40-pack-years history of cigarette smoking and does not use alcohol or drugs. Rectal examination shows a smooth, firm enlargement of the prostate without induration or asymmetry. Neurological examination shows no abnormalities. Urinalysis shows hematuria with isomorphic red blood cells. Laboratory studies show a serum creatinine of 1.5 mg/dl, and a PSA of 2 ng/ml. Which of the following is the most likely explanation for this patient's symptoms?

166. A 32-year-old male with type 1 diabetes and severe depression is brought to the emergency department because of a 2-day history of nausea and abdominal pain. His temperature is 37.6C (99.7F), blood pressure is 122/86 mmHg, respirations are 25/min and pulse is 88/min. His lab values are as follows: Blood pH 7.31 Pa02 90mm Hg PaC02 29 mmHg HCO3- 14 mEq/L Blood glucose 450 mg/dl Serum sodium 132 mEq/L Serum potassium 5.0 mEq/L Serum chloride 85mEq/L Blood urea nitrogen 19 mg/dl Serum creatinine 1.1 mg/dl Which of the following best describes this patient's acid-base status?

51. A 64-year-old woman presents to your office after falling in the grocery store earlier today. She says she was doing her usual shopping when she felt weak in her legs and fell down. She denies hitting her head, headache, or loss of consciousness, but does complain of low back pain. Her past medical history is significant for diabetes mellitus, hypertension, severe osteoporosis, chronic neck pain and congestive heart failure. She has had three transient ischemic attacks, each lasting 15-20 minutes and characterized by slurred speech, in the past. Her medications include insulin, lisinopril, carvedilol, alendronate, aspirin, and acetaminophen. Her blood pressure is 160/90 mmHg and her heart rate is 73/min. Physical exam reveals muscular weakness, increased deep tendon reflexes, and mildly decreased pinprick sensation in both lower extremities. Which of the following is most likely responsible?

Prolonged unopposed estrogen stimulation in an adult woman increases the risk of development of endometrial hyperplasia and subsequent carcinoma. Which of the following is the most common histologic appearance for this type of cancer?

A healthy 29-year-old gravida 2 woman at 39 weeks has been in labor for 3 hours. She had a positive vaginal-anal culture for GBS at 37 weeks' gestation. Which one of the following statements is correct?

A 19-year-old patient presents to your office with primary amenorrhea. She has normal breast and pubic hair development, but the uterus and vagina are absent. Diagnostic possibilities include which of the following?

A 30-year-old G3P3 is postoperative day 4 after a repeat cesarean delivery. During the surgery she received 2 units of packed red blood cells for a hemorrhage related to uterine atony. She is to be discharged home today. She complains of some yellowish drainage from her incision and redness that just started earlier in the day. She states that she feels feverish. She is breast-feeding. Her past medical history is significant for type 2 diabetes mellitus and chronic hypertension. She weighs 110 kg. Her vital signs are temperature 37.8C (100. 1 F), pulse 69 beats per minute, respiratory rate 18 breaths per minute, and blood pressure is 143/92 mm Hg. Breast, lung, and cardiac examinations are normal. Her mid line vertical skin incision is erythematous and has a foul-smelling purulent discharge from the lower segment of the wound. It is tender to touch. The uterine fundus is not tender. Which of the following is not a risk factor for her condition?

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

A previously healthy 6-year -old girl is brought to the office due to a 10-day history of persistent, thick, nasal discharge, nasal congestion, cough, and intermittent low-grade fever. She has had no vomiting, headache, earache, or rash. Her temperature is 37.2 C (98.9 F), blood pressure is 88/50 mmHg, pulse is 90/min, and respirations are 15/min. Physical examination shows clear tympanic membranes, congested posterior nasopharynx with thick, yellow and purulent mucus, and red, swollen nasal turbinates. Transillumination of the sinuses is equivocal. Palpation of the maxillary sinuses shows mild tenderness. Lungs are clearto auscultation. Which of the following organisms is the most common etiologic agent of this condition?

19) 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?

A 16-year -old African American male with sickle eel I 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 36.7C (98F), 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?

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?

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, all 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?

A 6-week-old male infant, who was born at 32 weeks' gestation with a birth weight of 1 500 g, has had an average weight gain of 8 g/day since birth. He takes an iron-fortified formula that is 24kcal/oz. His calorie intake is about 12 5kcal/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?

549) 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?