CK- NBME 11 – Block 3

A previously healthy 3-month-old boy is brought to the physician because of a 24-hour history of increasingly rapid breathing, difficulty feeding, and progressive fussiness. He has not had fever, but he has received acetaminophen to ease his fussiness. He receives no other medications. He is exclusively breast-fed. He is alert and pale and appears anxious. His pulse is 250/min, respirations are 68/min, and blood pressure is 80/50 mm Hg. He is not using accessory muscles of respiration. Pulse oximetry on room air shows an oxygen saturation of 99%. Capillary refill time is 2 seconds. Examination shows pink lips and moist oral mucosa. The lungs are clear to auscultation. No murmurs or gallops are heard on cardiac examination. The precordium is hyperdynamic. The abdomen is soft. The liver edge is palpated 3 cm below the right costal margin, and the spleen tip is palpated 2 cm below the left costal margin. Distal pulses are palpable. Laboratory studies show:

Hemoglobin: 9 g/dL

Hematocrit: 27%

Leukocyte count: 8000/mm³

Platelet count: 212,000/mm³

An ECG is shown:

Which of the following is the most likely diagnosis?

A 17-year-old boy is brought to the emergency department 30 minutes after he was thrown through a window during an altercation. He has no history of serious illness and takes no medications. He is alert and fully oriented. He reports moderate pain in his right arm and hand. His pulse is 110/min, respirations are 22/min, and blood pressure is 110/70 mm Hg. Pulse oximetry on 2 L/min of oxygen by nasal cannula shows an oxygen saturation of 98%. Examination shows superficial abrasions over the right side of the face. A 4 x 4-cm glass shard protrudes from the right upper extremity 2 cm proximal to the medial epicondyle; the extremity is cool and pale, and radial and ulnar pulses are not palpable. Which of the following is the most appropriate next step in management?

A 58-year-old woman with osteoarthritis comes to the office because of a 1 -week history of fatigue. She also has had difficulty at work climbing stairs and putting away office supplies in cabinets above shoulder level. She says that during this time her arthritis pain has worsened and has spread to her shoulders, hips, and upper legs. She attributes her fatigue to poor sleep because of aching of her arms and legs. During a routine examination 6 months ago, hypertension and hypercholesterolemia were diagnosed and she was started on chlorthalidone, simvastatin, aspirin, vitamin D, calcium, and a multivitamin. Her only additional medication is ibuprofen. The patient smoked two packs of cigarettes daily for 30 years but quit 6 months ago in an attempt to improve her health after her sister had “a major heart attack.” At that time, the patient also stopped drinking alcoholic beverages and decreased her coffee consumption from 4 cups to 2 cups daily. She is 168 cm (5 ft 6 in) tall and weighs 73 kg (160 lb); BMI is 26 kg/m2. Vital signs are temperature 36.4°C (97.6°F), pulse 84/min, respirations 16/min, and blood pressure 122/78 mm Hg. The patient appears anxious but is not in acute distress. Musculoskeletal examination shows no edema, erythema, or deformity with minimal tenderness of all major joints. Active and passive range of motion is full. During passive range of motion testing, the patient reports pain where her upper arms and upper legs are grasped. The remainder of the physical examination discloses no abnormalities. Which of the following studies is most likely to establish the diagnosis?

A 37-year-old man is brought to the emergency department after his motorcycle ran into the back of a truck at high speed. He was wearing a helmet. On arrival, his neck is immobilized in a cervical collar, and intravenous fluids are being administered. Paramedics report that at the scene he appeared to be intoxicated. He is alert and talking. His breath smells of alcohol. His pulse is 130/min, respirations are 30/min, and blood pressure is 100/60 mm Hg. The lungs are clear to auscultation. Heart sounds are normal. The abdomen is distended and tender. There is blood at the urethral meatus. Ultrasonography shows blood in the abdomen. An x-ray of the pelvis shows fractures of the pubic rami and ischial and ilial fractures on the right. Which of the following is the most appropriate next step in management?

A 25-year-old woman comes to the emergency department because of nausea, diarrhea, and anxiety for 2 days. She also has noticed dizziness and tingling sensations shooting down her forearms. Her sleep and appetite have been normal. She has a 3-year history of social phobia well controlled for the past year with paroxetine. She is attending an out-of-town conference and forgot to pack her medication; her last dose was 3 days ago. She does not drink alcohol or use illicit drugs. She is 163 cm (5 ft 4 in) tall and weighs 80 kg (176 lb); BMI is 30 kg/m2. Her temperature is 37°C (98.6°F), pulse is 80/min, and blood pressure is 110/75 mm Hg. Physical examination shows no other abnormalities. Mental status examination shows an irritable mood with a full range of affect. Her speech is of normal rate and rhythm. There is no evidence of suicidal ideation or hallucinations. She can recall three of three objects after 5 minutes. Long-term memory is intact. Serum studies show no traces of paroxetine. Which of the following is the most appropriate next step in management?

A 72-year-old man with lung cancer comes to the physician because of a 2-month history of weakness in his legs. He also has had dry mouth, constipation, and tingling of his hands and feet during this period. He received radiation therapy 3 weeks ago and is currently undergoing chemotherapy. He has smoked two packs of cigarettes daily for 50 years. His temperature is 37°C (98.6°F), pulse is 86/min, respirations are 20/min, and blood pressure is 126/84 mm Hg. There is mild bilateral ptosis, which does not worsen after upward gaze for 1 minute. Ocular movements are full. Oral mucosa is dry. There is mild weakness of hip flexion bilaterally. After several attempts, he can rise from a chair with his arms folded across his chest. Deep tendon reflexes are absent. Sensation is intact. Which of the following is most likely to confirm the diagnosis?

A 72-year-old woman with a 30-year history of type 2 diabetes mellitus comes to the physician because of pain and swelling of her left foot since a blister on the bottom of her left foot broke 2 weeks ago. Her temperature is 37.2°C (99°F). Examination shows swelling and erythema of the left distal leg, ankle, and foot; there is a 2-cm ulcer at the base of the heel with an overlying black eschar. Peripheral pulses are decreased bilaterally. Capillary refill time is greater than 3 seconds. The ulcer is debrided, and a sterile probe is inserted until the base touches bone. Which of the following is the most likely cause of these findings?

A 37-year-old man with end-stage Duchenne muscular dystrophy is scheduled for discharge from the hospital after treatment for pneumonia. He has been admitted to the hospital four times over the past 6 months for recurrent pneumonia. Over the past 3 years, he has received mechanical ventilation and has used a wheelchair. His life expectancy is less than 6 months. The patient tells the physician that he is “tired of living like this” and requests a do-not-resuscitate order with no further antibiotics. He has been considering this decision for 3 weeks but has not discussed it with his family. On mental status examination, he shows sadness about his health but has a normal thought process. He expresses no ambivalence about his decision. Which of the following is the most appropriate next step in management?

 A 12-year-old boy is brought to the physician for a routine follow-up examination. He received the diagnosis of chronic renal failure secondary to glomerulonephritis 2 years ago. He has hypertension controlled with an ACE inhibitor. He is at the 10th percentile for height and weight. Examination shows mild edema of the lower extremities. His mother asks about ways to minimize complications of his renal failure. Which of the following is the most appropriate recommendation?

A 13-year-old girl is brought to the physician because her mother is concerned that her daughter has never had a menstrual period. She is at the 80th percentile for height and 75th percentile for weight. Breast and pubic hair development is Tanner stage 2. Examination shows no other abnormalities. Which of the following is the most appropriate next step in management?

A 27-year-old woman comes to the physician because of a 2-week history of intermittent substernal chest pain. She states that the pain is worsened by swallowing solids or liquids. She has a 10-year history of intravenous drug use. Her temperature is 37°C (98.6°F), pulse is 80/min, respirations are 20/min, and blood pressure is 120/80 mm Hg. Examination shows poor dentition and multiple 1- to 2-cm lymph nodes in the cervical and inguinal regions. Cardiac examination shows no abnormalities. Which of the following is the most appropriate next step in diagnosis?

A previously healthy 42-year-old woman has had generalized weakness, lethargy, and double vision for 2 weeks. Examination shows no other abnormalities. X-rays of the chest show an upper anterior mediastinal mass. Which of the following is the most likely diagnosis?

A 67-year-old woman comes to the emergency department 6 hours after she noticed a red rash over her arms and abdomen. She has had nosebleeds during the past week. She has a 1-month history of nightly temperatures to 38.3°C (101°F) with night sweats. Eight years ago, she had ovarian cancer and underwent total abdominal hysterectomy, bilateral salpingo-oophorectomy, and omentectomy followed by chemotherapy and filgrastim (GCSF) therapy. She has received conjugated estrogen therapy since the operation. There has been no recurrence of ovarian cancer. She is 168 cm (5 ft 6 in) tall and weighs 59 kg (130 lb); BMI is 21 kg/m2. Her temperature is 38.3°C (101 °F), pulse is 120/min, respirations are 20/min, and blood pressure is 100/70 mm Hg. Examination shows a diffuse petechial rash over the upper extremities and abdomen. The cervical lymph nodes are shoddy and slightly enlarged. Pelvic examination shows no abnormalities. Her hematocrit is 22%, leukocyte count is 30,000/mm3, and platelet count is 30,000/mm3. A blood smear shows immature myeloblasts. Which of the following is the most likely cause of this patient’s current condition?

 A healthy 16-year-old girl is brought to the physician for an examination prior to participation in school sports. She has no history of serious illness, and she is doing well in school. Menarche occurred at the age of 12 years; menses occur at regular 28-day intervals. Her mother and maternal grandmother have hypothyroidism treated with levothyroxine. The patient appears well. She is 168 cm (5 ft 6 in) tall and weighs 75 kg (165 lb); BMI is 27 kg/m2. Her temperature is 37°C (98.6°F), pulse is 72/min, respirations are 18/min, and blood pressure is 96/70 mm Hg. Examination shows no exophthalmos or lid lag. The thyroid gland is moderately enlarged and firm, but no nodules are palpable. Cardiopulmonary examination shows no abnormalities. The extremities are warm and well perfused. Deep tendon reflexes are 2+, but the Achilles relaxation phase is delayed. Serum studies show:

Thyroid-stimulating hormone: 56 µU/mL

Thyroxine (T₄): 6 µg/dL

Antithyroid peroxidase antibodies: >1:1000 (N < 1:20)

Thyroglobulin antibodies: 1:500 (N < 1:20)

Which of the following is the most likely explanation for these findings?

A previously healthy 52-year-old man comes to the physician because of a 6-month history of difficulty swallowing solids and liquids. He has had a 2.3-kg (5-lb) weight loss during this period. Examination shows no abnormalities. An upper gastrointestinal series with barium contrast is shown. Which of the following is the most likely diagnosis?

A previously healthy 4-year-old boy is brought to the physician because of increasing left ear pain for 2 weeks. His temperature is 38.5°C (101.3°F). Examination of the left ear shows an erythematous, bulging tympanic membrane and an edematous auditory canal with a small amount of mucopurulent discharge. The ear appears to be displaced laterally, and there is moderate tenderness in the area behind the ear. Examination of the right ear shows no abnormalities. A 1-cm, freely mobile, nontender mass is palpated over the left anterior neck. Examination of the pharynx shows no abnormalities. Which of the following is the most appropriate next step in management?

A 21-year-old woman comes to the physician because she has not had a menstrual period since she stopped using an oral contraceptive 10 months ago. Menarche was at the age of 14 years, and menses had occurred at regular 28-day intervals before starting an oral contraceptive 3 years ago. She is not sexually active. She is 165 cm (5 ft 5 in) tall and weighs 63 kg (140 lb); BMI is 23 kg/m2. Her blood pressure is 120/58 mm Hg. Examination shows no hirsutism or other abnormalities. Serum studies show a thyroid- stimulating hormone concentration of 3 μU/mL, prolactin concentration of 20 ng/mL, and free thyroxine concentration of 2 ng/dL (N=0.8-2.4). A progestin challenge test shows withdrawal bleeding. Which of the following is the most likely diagnosis?

A 72-year-old man is brought to the emergency department by his wife because of fever and chills for 2 hours. He visited the physician 2 days ago because of burning with urination, and urine cultures were ordered. He was an artillery officer 40 years ago, and his wife says that his hearing is deteriorating. He has a sulfa allergy. He appears moderately ill. His temperature is 38.3°C (101°F). Examination shows left costovertebral angle tenderness. His leukocyte count is 15,000/mm3 with a shift to the left. Urinalysis shows many bacilli. Urine culture and sensitivity show an organism that is sensitive only to nitrofurantoin, gentamicin, amikacin, tobramycin, trimethoprim-sulfamethoxazole, and ciprofloxacin. Which of the following is the most appropriate pharmacotherapy?

A 19-year-old man comes to the physician because of frequent nosebleeds over the past 3 weeks. He has bipolar disorder currently well controlled with lithium carbonate, bupropion, and valproic acid. Physical examination shows no abnormalities except for dried blood in the nares. Mental status examination shows an anxious mood and slight motor restlessness. Serum studies show a lithium carbonate concentration of 1.3 mEq/L (therapeutic range=0.6-1.2), and valproic acid concentration of 77 pg/mL (therapeutic range=40-100). Which of the following is the most appropriate next step in management?

A 52-year-old woman comes to the physician because of tremors in her hands for 4 months. She only fills teacups halfway to avoid spilling, and she has difficulty lifting a spoonful of soup to her mouth without spilling it. Her children noticed tremors of her head 5 years ago. She has no history of serious illness and takes no medications. She is 168 cm (5 ft 6 in) tall and weighs 56 kg (123 lb); BMI is 20 kg/m2. Her temperature is 37°C (98.6°F), pulse is 80/min, respirations are 12/min, and blood pressure is 110/70 mm Hg. Examination shows a tremor of the outstretched hands bilaterally; the amplitude of the tremor increases with finger-nose testing. The tremor resolves at rest. Muscle strength and tone are intact, and her gait is normal. Which of the following is the most appropriate pharmacotherapy?

A 32-year-old woman, gravida 1, para 1, comes to the physician for a postpartum examination 6 weeks after an uncomplicated vaginal delivery at home. She feels well, and her postpartum course has been uncomplicated. During her pregnancy, results of a serum rubella titer were reported as nonimmune. Physical examination today shows no abnormalities. Which of the following is the most appropriate next step in management?

A 32-year-old woman comes to the emergency department because of progressive shortness of breath during the past week. She now becomes short of breath after walking 10 feet. She says that she thinks she has had fever but has not taken her temperature. She does not think she has been in contact with any ill persons. She has smoked one pack of cigarettes daily for 15 years. She does not drink alcohol but has used intravenous heroin for 10 years; she rarely shares or sterilizes needles. She lives in Massachusetts and has not traveled outside of the state in 8 years. She is in mild respiratory distress. She is 168 cm (5 ft 6 in) tall and weighs 50 kg (110 lb); BMI is 18 kg/m2. Her temperature is 38°C (100.4°F), pulse is 80/min, respirations are 18/min, and blood pressure is 100/70 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 93%. Diffuse crackles are heard bilaterally. There is no peripheral edema. After she walks 50 feet, her oxygen saturation decreases to 83%. Her leukocyte count is 4800/mm3 (70% segmented neutrophils, 2% bands, 26% lymphocytes, and 2% eosinophils). An x-ray of the chest shows diffuse alveolar infiltrates bilaterally. Which of the following is the most likely diagnosis?

A 67-year-old man with aortic stenosis comes to the physician for prophylaxis before undergoing a dental procedure. He has a history of aortic valve replacement; he is currently asymptomatic. He had an episode of hives several years ago after treatment with penicillin. Vital signs are within normal limits. Examination shows a grade 2/6, systolic ejection murmur; no gallops are heard. The remainder of the examination shows no abnormalities. Which of the following is the most appropriate antibiotic for prophylaxis?

Thirty-six hours after cesarean delivery because of prolonged labor, a 22-year-old woman has abdominal cramping and nausea and vomiting. Her temperature is 38.8°C (101.8°F), pulse is 98/min, and blood pressure is 110/64 mm Hg. Examination shows diffuse lower abdominal tenderness with some voluntary guarding but no rebound. The incision is clean, dry, and intact. Her leukocyte count is 15,000/mm3. A urinary catheter is in place; urinalysis shows multiple RBCs. Which of the following is the most likely diagnosis?

A 9-year-old boy is brought to the physician by his mother because of a 1-month history of intermittent nonproductive cough. The cough is exacerbated with exercise and is worse at night. He has not had fever. The patient’s father received the diagnosis of asthma as a child. The patient’s temperature is 37.3°C (99.1 °F), pulse is 90/min, respirations are 22/min, and blood pressure is 108/70 mm Hg. Examination shows no other abnormalities. Pulmonary function tests are most likely to show which of the following findings in this patient?

A 19-year-old college student comes to the student health center for a physical examination prior to participation in a school intramural basketball league. She has been generally healthy. She says that she is a strict vegetarian and does not eat any meat, eggs, or dairy products. She takes an iron supplement daily. She takes no other medications. She is 162 cm (5 ft 4 in) tall and weighs 45 kg (100 lb); BMI is 17 kg/m2. Vital signs are normal. Physical examination shows no abnormalities. Which of the following additional supplements is most appropriate to recommend at this time?

A 72-year-old woman comes to the emergency department because of a 2-week history of increased thirst and frequent urination. She says that her symptoms have been getting worse. She drinks copious amounts of water and now urinates every 1 to 2 hours. She has hypertension controlled with ramipril. She had a myocardial infarction 6 years ago. On arrival, she appears dehydrated. Her temperature is 36°C (96.8°F), pulse is 110/min, and blood pressure is 100/70 mm Hg. Examination shows dry mucous

Hematocrit: 47%

Serum:

Na⁺: 125 mEq/L

K⁺: 3.5 mEq/L

Cl⁻: 95 mEq/L

HCO₃⁻: 24 mEq/L

Urea nitrogen: 30 mg/dL

Glucose: 700 mg/dL

Creatinine: 1.8 mg/dL

Which of the following is the most likely cause of this patient’s serum sodium concentration?

 A 4-year-old boy is brought to the physician because of scalp lesions that have been increasing in size during the past week. He went for a nature walk with his day-care class 10 days ago. Examination shows scattered papules with some scaly areas on the scalp; the surrounding hair is broken near the base with mild alopecia. Which of the following is most likely to have prevented this condition?

 A 24-year-old woman comes to the physician because of fever, headache, and purulent nasal discharge for 5 days. She has had recurrent sinus infections since the age of 17 years. She has a 3-year history of chronic nasal stuffiness and a morning cough productive of 2 to 3 teaspoons of purulent sputum daily. She was hospitalized for treatment of pneumonia 1 year ago. Her temperature is 37.8°C (100°F), pulse is 84/min, respirations are 16/min, and blood pressure is 110/72 mm Hg. Examination shows edema of the nasal mucosa and a creamy yellow nasal exudate. The lungs are clear to auscultation. The spleen tip is palpated at the left costal margin. Which of the following is the most appropriate next step to confirm the mechanism for the recurrent infections?

 An 18-year-old woman who is a US Army recruit comes to the troop medical clinic because of a 4-day history of increasingly severe cramping and swelling of her left foot. She began basic training 10 days ago. She had not been physically active before joining the army. Initially, she was able to keep up with the training regimen, but she soon developed pain in her forefoot as the intensity of the exercise increased. Vital signs are within normal limits. She is 165 cm (5 ft 5 in) tall and weighs 68 kg (150 lb); BMI is 25 kg/m2. Examination of the left foot shows tenderness to palpation of the dorsal aspect of the fifth metatarsal; there is minimal swelling. Movement of the involved toe elicits pain. X-ray of the left foot shows no abnormalities. Which of the following is the most appropriate next step in management?

A hospitalized 65-year-old woman is prepared for discharge 15 days after undergoing uncomplicated surgical repair of the ventricular septum following an anterior ST-segment elevation myocardial infarction. Her postoperative course has been uncomplicated. She has hypertension and hyperlipidemia. Her medications are clopidogrel, lisinopril, metoprolol, atorvastatin, and aspirin. Vital signs are within normal limits. Examination shows a clean, dry surgical incision. Echocardiography shows an ejection fraction of 50%. In addition to continuation of the medication regimen, which of the following interventions is most likely to decrease this patient’s risk for a repeat myocardial infarction?

 A 15-year-old girl is brought to the office by her father because of a 2-month history of yellowing of her eyes. She has no history of serious illness and takes no medications. She is at the 50th percentile for height, weight, and BMI. Vital signs are within normal limits. Examination shows conjunctival icterus. Serum studies show a total bilirubin concentration of 4 mg/dL and a conjugated bilirubin concentration of 3 mg/dL. Results of other liver function tests are within the reference ranges. Ultrasonography of the liver shows no abnormalities. Which of the following is the most likely diagnosis?

 Three days after undergoing open fixation of a right hip fracture, a 77-year-old woman has progressive edema of the right lower extremity. She has no history of serious illness. Her medications are oxycodone, enoxaparin, and docusate. Her temperature is 38.0°C (100.4°F), pulse is 72/min, respirations are 14/min, and blood pressure is 140/80 mm Hg. There is 3+ pitting edema of the right lower extremity from the foot to the hip. Which of the following is the most likely set of findings on venous duplex ultrasonography?

A 39-year-old woman, gravida 3, para 2, is brought to the emergency department because of a 3-hour history of moderate to severe abdominal cramps and vaginal bleeding with clots. Her last menstrual period was 9 weeks ago. Menses previously occurred at regular 30-day intervals and lasted 7 days. Her previous pregnancies and deliveries were uncomplicated. She has no history of serious illness and takes no medications. She is currently homeless and seeking shelter. Her temperature is 37.3°C (99.1 °F), pulse is 103/min, respirations are 14/min, and blood pressure is 130/82 mm Hg. Examination shows tenderness to palpation of the mid lower abdomen. Bowel sounds are normal. The uterus is tender to palpation and consistent in size with a 9-week gestation. Pelvic examination shows normal external genitalia, moderate clots in the vaginal vault, and a closed cervical os. There is no adnexal tenderness or masses. Her hemoglobin concentration is 7.9 g/dL. Pelvic ultrasonography shows an intrauterine pregnancy consistent in size with a 9-week gestation; no fetal heart motion; a small amount of fluid in the cul-de-sac; and a subchorionic hemorrhage. Which of the following is the most appropriate next step in management?

 A 57-year-old man with hypertension comes to the office for a routine examination. He feels well. Four years ago, he had basal cell carcinoma on his nose treated with excision. Colonoscopy 5 years ago showed a tubular adenoma. Fifteen years ago, he underwent appendectomy for appendicitis. His medications are hydrochlorothiazide, fish oil supplementation, and a multivitamin. He received the influenza virus vaccine 6 months ago and the tetanus-diphtheria-acellular pertussis vaccine 5 years ago. He does not smoke cigarettes. He drinks 8 to 16 oz of wine nightly and exercises four to five times weekly. He is 183 cm (6 ft) tall and weighs 86 kg (190 lb); BMI is 26 kg/m2. His pulse is 80/min, and blood pressure is 128/88 mm Hg. Examination shows scattered pale nevi over the chest and back. No other abnormalities are noted. Results of serum lipid studies from 6 months ago are shown:

Cholesterol, total: 201 mg/dL

HDL-cholesterol: 42 mg/dL

LDL-cholesterol: 120 mg/dL

Triglycerides: 180 mg/dL

Which of the following is the most appropriate next step in management?

A metropolitan city has a higher than average rate of obesity-related disability compared with other cities of similar size. The city’s director of public health would like to prevent future obesity-related complications for this city’s residents. Which of the following is the most appropriate strategy for primary prevention of obesity in this population?

 A 4-month-old girl is admitted to the hospital because of a 7-day history of progressive cough. During the past 2 days, the cough has been associated with gagging, difficulty breathing, and perioral cyanosis. Between coughing episodes, she is alert and not in respiratory distress. She was born at term following an uncomplicated pregnancy and spontaneous vaginal delivery. Her mother has a 3-week history of nonproductive cough treated with over-the-counter cough syrup. The patient receives no medications. She appears well nourished. Her temperature is 38°C (100.4°F), pulse is 120/min, and respirations are 45/min. Pulse oximetry on room air shows an oxygen saturation of 98%. The lungs are clear to auscultation, and air movement is good. During an observed coughing episode, the patient’s lips become cyanotic. Pulse oximetry on room air during the episode shows an oxygen saturation of 85%. Which of the following is the most likely infectious agent?

A 44-year-old woman comes to the office with her husband because of a 2-week history of an increasingly severe tremor in her right hand. She is right-handed. The tremor makes it difficult for her to brush her teeth or hold a coffee cup. She also has had a slowed gait during this time. She says she is afraid that she has Parkinson disease like her father. She has no history of serious illness and takes no medications. She works as an executive at an advertising firm. Her husband says, “My wife is coping as best she can, especially considering how stressful her work is.” Neurologic examination of the patient shows a resting tremor of the right hand. The tremor increases in severity on finger-nose testing. The tremor decreases when she manipulates a coin in her left hand. Her gait is slow, but balance is intact. The remainder of the examination shows no abnormalities. An MRI of the brain shows no abnormalities. Which of the following is the most likely diagnosis?

A 22-year-old woman is brought to the office by her parents because of a 9-month history of observing her eyebrows in mirrors for up to an hour at a time. She frequently stares at her eyebrows, sometimes separating the hairs with tweezers and examining the skin underneath. She never plucks them. Her behavior has caused her parents to have to remind her to eat meals and go to class. She has fallen behind in her schoolwork and has stopped calling her friends. She appears disheveled. She is 168 cm (5 ft 6 in) tall and weighs 57 kg (125 lb); BMI is 20 kg/m2. Physical examination shows no abnormalities. On mental status examination, she is alert and fully oriented. She is cooperative and articulate but makes poor eye contact. She describes her mood as “okay.” Her affect is flat. Her thought process is linear except when discussing her eyebrows. During the examination, she sees her reflection in a mirror and stares at her eyebrows. She says she is “reading” the hair follicle and direction patterns; she is worried that they might change, which would have dire consequences for her and her family. She says the “reading” may take much time because she often loses track of her progress and must begin again. Which of the following is the most likely diagnosis?

A healthy 15-year-old girl is brought to the office because she has never had a menstrual period. She takes no medications and has no known allergies. She is 152 cm (5 ft) tall and weighs 48 kg (105 lb); BMI is 21 kg/m2. Her blood pressure is 98/55 mm Hg. Breast and pubic hair development is Tanner stage 1. Pelvic examination shows normal-appearing external genitalia and a small uterus. Serum studies show a follicle-stimulating hormone concentration of 56 mlU/mL and luteinizing hormone concentration of 42 IU/mL. Which of the following is the most appropriate next step in diagnosis?

A 63-year-old woman comes to the emergency department because of a 1-week history of progressive shortness of breath on exertion and swelling of her legs. During this time, she has been using two pillows to sleep. Her pulse is 100/min, respirations are 24/min, and blood pressure is 120/80 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 93%. There is jugular venous distention. Bilateral basilar crackles are heard over the lower lungs. On cardiac examination, a grade 3/6 holosystolic murmur is heard best over the apex; an S3 gallop is heard. There is 3+ pitting edema of the lower extremities. Echocardiography shows an ejection fraction of 30%. In addition to furosemide, which of the following is the most appropriate pharmacotherapy at this time?

A 52-year-old woman comes to the physician 2 weeks after noticing a painless lump in her right breast. Mammography 6 months ago showed no abnormalities. She has no history of serious illness and takes no medications. A 1,5-cm, firm, irregular, nontender mass is palpated in the lower outer quadrant of the right breast. An ultrasonography- guided core biopsy specimen shows infiltrating ductal carcinoma. The patient is concerned about the accuracy of mammography and wishes to know its failure rate in diagnosing breast cancer. Which of the following is the most appropriate test characteristic to determine this answer?

 A 22-year-old woman comes to the emergency department because of a 3-hour history of right-sided chest pain. During the past 3 months, she has had temperatures to 38.1°C (100.5°F), marked fatigue, easy bruising, and photosensitivity of the skin, especially over her cheeks. She has had a 7-kg (15-lb) weight loss during this time. She has a 6-month history of aching of her hands and knees. This past winter, she noticed that her fingers became blue on exposure to cold weather and then would become painful and red when she returned indoors. She has no history of serious illness and takes no medications. She has not traveled outside the USA. She is alert and fully oriented. Her temperature is 37.2°C (99°F), pulse is 92/min, respirations are 20/min, and blood pressure is 110/60 mm Hg. A photograph of the face is shown. A low-pitched grating sound is heard over the right lateral lung field. The sound is louder on inspiration but is present during expiration. The sound stops when the patient holds her breath. Cardiac and abdominal examinations show no abnormalities. There is no peripheral edema, clubbing, or cyanosis. A chest x-ray shows no abnormalities. Which of the following is the most appropriate next step in management?

A 27-year-old woman comes to the physician because of a 2-week history of recurring bifrontal headaches and vomiting. The headaches are not relieved by over-the-counter analgesics. She has not had visual changes or other neurologic symptoms. She has no history of serious illness and takes no medications. She is alert and fully oriented. She is 157 cm (5 ft 2 in) tall and weighs 104 kg (230 lb); BMI is 42 kg/m2. Her pulse is 78/min, and blood pressure is 114/72 mm Hg. Funduscopic examination findings are shown. Visual acuity is 20/20 bilaterally. Neurologic examination shows no focal findings. A CT scan of the head shows no abnormalities. Which of the following is the most appropriate next step in management?

 A study is conducted to compare the efficacy of cholesterol-lowering medications X and Y. A total of 500 patients with a serum cholesterol concentration greater than 200 mg/dL are enrolled in the study. Three hundred patients are randomly assigned to receive medication X, and 200 patients are randomly assigned to receive medication Y. Serum cholesterol concentrations are measured for both groups after 6 months of therapy. Which of the following statistical tests will be most helpful in comparing mean serum cholesterol concentrations of both groups?

A 92-year-old man is admitted to the hospital because of a 24-hour history of severe abdominal pain and distention, nausea, and vomiting. One week ago, he was discharged from the hospital after repair of a left hip fracture. His postoperative course had been uncomplicated. He has hypertension and cataracts. Medications are hydrochlorothiazide, hydrocodone with acetaminophen, aspirin, and multivitamins. His temperature is 37.7°C (99.9°F), pulse is 100/min, respirations are 14/min, and blood pressure is 146/80 mm Hg. The abdomen is distended and diffusely tender. Bowel sounds are decreased. Rectal examination shows mucus, scant stool, and no masses. Test of the stool for occult blood is negative. An x-ray of the abdomen shows no free air under the diaphragm; there is marked colonic dilation from the cecum to the anus with stool and air-fluid levels. Which of the following is the most likely diagnosis?

An 18-year-old primigravid woman at 39 weeks’ gestation is admitted to the hospital in labor. Contractions occur every 5 minutes and last 1 minute. Her first prenatal visit was 1 week ago. She was treated for syphilis 1 year ago. Her only current medication is a prenatal vitamin, which she started 1 week ago. She uses cocaine and heroin. She has had sexual intercourse with multiple male partners. They use condoms inconsistently. The patient appears well. Vital signs are within normal limits. On pelvic examination, the cervix is 4 cm dilated and 50% effaced. The uterus is consistent in size with a 39-week gestation. No abnormalities are noted. Laboratory studies show:

HBsAg: positive

Anti-HBs: negative

Rapid plasma reagin: negative

Fluorescent treponemal antibody assay: positive

Herpes simplex virus antibody assay: positive IgG at 1:640

HIV ELISA: positive

Vaginal testing for group B streptococcus and cervical testing for Chlamydia trachomatis and Neisseria gonorrhoeae are negative. Intrapartum pharmacotherapy should be administered to prevent which of the following in the newborn?

A 62-year-old Asian man comes to the physician because of a 10-month history of a dark lesion on the nail of his right big toe. One year ago, he dropped something on the toe, but he is unsure if this accident caused the lesion. Initially, the lesion was a 0.5-cm, longitudinal, black streak near the side of the toenail. During the past 2 months, the lesion has enlarged and has spread to the nail fold. He has no history of serious illness and takes no medications. A photograph of the right big toe is shown. Examination shows no other abnormalities. Which of the following is the most likely diagnosis?

A 22-year-old man has a temperature of 39.5°C (103.1°F) 1 hour after initiation of a transfusion of packed red blood cells for a hemoglobin concentration of 7 g/dL. Yesterday, he underwent open reduction and internal fixation of a fractured femur sustained in a motor vehicle collision. He received prophylactic cefazolin prior to the operation and is now receiving enoxaparin. He is otherwise healthy and has no known allergies. The remainder of the vital signs are within normal limits. Examination shows no abnormalities. Which of the following is the most appropriate next step in management?

A study is conducted to assess the impact of obesity on the risk for cerebral infarction. The investigator enrolls 100 participants with a history of cerebral infarction and 100 healthy participants. The investigator determines each participant’s weight. The results show:

Which of the following represents the odds ratio for the relationship between obesity and cerebral infarction?