A 40-year-old woman has had hypercalcemia for 1 year and recently passed a renal calculus. Serum parathyroid hormone and calcium concentrations are increased, and serum phosphate concentration is decreased. Parathyroid hormone most likely causes an increase in the serum calcium concentration by which of the following mechanisms?

The graph shows the relationship between serum leptin concentration and BMI, expressed as (weight in kg) / (height in meters)2 for eight patients labeled A through H. The dashed lines indicate the upper and lower limits of normal. Which of the following patients most likely has primary leptin deficiency?

A 59-year-old man comes to the physician because of a 3-month history of progressive difficulty swallowing; he has had a 6.8-kg (15-lb) weight loss during this period. He has smoked 1 pack of cigarettes daily for 40 years and consumes four to six beers daily. He is cachectic. Bilateral wheezes are heard on auscultation of the chest. A chest x-ray shows enlargement of the paratracheal and hilar lymph nodes. Subsequent endoscopy shows a 6-cm mass in the mid esophagus. The mass is centrally ulcerated with an elevation of the surrounding mucosal rim. Examination of a biopsy specimen of the mass is most likely to show neoplastic cells with which of the following?

A 1 -year-old boy is brought to the emergency department because of a 6-day history of temperatures to 39.4°C (103°F) and a 2-day history of a severe diaper rash and swelling of his hands and feet. His temperature is now 39.4°C (103°F). A photograph of the genital area is shown. The face and lips appear red and the conjunctivae appear injected. There is bilateral cervical lymphadenopathy. The lungs are clear to auscultation. Cardiac examination shows an S3 gallop with no murmur. There is edema and erythema of the hands and feet. Which of the following pathologic findings is most likely in this patient?

A 28-year-old woman, gravida 3, para 2, comes to the physician to request an elective abortion 2 days after she received a positive home pregnancy test result. Her last menstrual period was 6 weeks ago. Ultrasonography shows a uterus consistent in size with a 6-week gestation. After counseling, she decides to undergo a medication-induced abortion rather than a surgical abortion. An oral medication is administered, and she is instructed to return to the office in 2 days to receive a second medication. The first drug administered most likely belongs to which of the following classes?

In an experimental design evaluating assays for the bactericidal effect of inflammatory cells, which of the following compounds is considered the most efficient in the killing of bacteria by neutrophils?

A 40-year-old woman has easy bruising and menorrhagia. Platelet count is 100,000/mm3, and bleeding time is prolonged. Factor VIII (antihemophilic factor) concentration is decreased, and platelet adhesion to collagen is abnormal. Which of the following is the most likely diagnosis?

A 57-year-old man is brought to the emergency department because of a 2-hour history of severe abdominal pain and vomiting. Abdominal examination shows diffuse tenderness. ACT scan of the abdomen and abdominal radiograph are shown; the arrows indicate an abnormality. The most likely cause of these findings is perforation of which of the following structures?

A 15-year-old girl with acute myelogenous leukemia undergoes a bone marrow transplant procedure. Her 19-year-old brother is the donor. Blood group and human leukocyte antigen (HLA) typing of patient and donor leukocytes are:

Three weeks later, she develops a temperature of 37.4°C (99.3°F); a diffuse, erythematous rash over most of the body, including the palmar and plantar surfaces; and watery diarrhea. Serum studies show an AST activity of 120 U/L (N=5-55) and ALT activity of 180 U/L (N=5-45). Which of the following is the most likely diagnosis?

A 36-year-old man comes to the physician after he noticed a dark lesion on his back. Physical examination shows a dark, irregularly shaped, raised region on the back. He has a history of frequent sun exposure at the beach. A biopsy specimen of the region confirms the diagnosis of a melanoma. Which of the following embryonic tissues most likely formed this tumor?

A 55-year-old man comes to the office because of a 7-year history of red, dry, itchy skin over his back and buttocks. Use of emollients and topical corticosteroids has not improved his symptoms. He has no other history of major medical illness. His vital signs are within normal limits. Physical examination shows the findings in the photograph. Laboratory studies show eosinophilia and increased serum concentrations of IgA and IgE. Malignant transformation of which of the following cell types is the most likely cause of the findings in this patient?

A 40-year-old woman comes to the physician because of a 2-month history of increasing redness around her nose and cheeks, and pimples around her mouth. She appears very upset and tells the physician, “I look like a teenaged Santa Claus.” Which of the following initial responses by the physician is most appropriate?

A 17-year-old boy with chronic renal insufficiency undergoes a unilateral nephrectomy. A photograph of the resected kidney is shown. Which of the following pathologic processes is most likely present in the kidney?

A 25-year-old woman at 38 weeks’ gestation undergoes an oxytocin stress test to evaluate the integrity of the placental labor with oxytocin is started. Treatment with oxytocin is most likely to activate which of the following substances in this

A healthy 28-year-old woman participates in an exercise study. Several physiologic variables are measured as she runs on a treadmill. The ambient room temperature is 75°F. She reaches a steady state that increases her oxygen consumption threefold. She continues to exercise at that level for 20 minutes. During the first 5 minutes of exercise, the vascular resistance of which of the following is likely to show the greatest increase from resting values in this volunteer?

A 68-year-old man with dementia, Alzheimer type, has improvement in memory and cognition with donepezil therapy. Which of the following is the most likely mechanism of this beneficial effect?

A 60-year-old man develops palpitations over a 6-week period during which he has been drinking approximately 8 cups of coffee per day. A rhythm strip from his ECG is shown. Which of the following is most likely responsible for the palpitations in this man?

A healthy 21 -year-old woman is concerned that her son will develop a familial neurologic disorder. Her older brother died at the age of 45 years after developing restlessness, forgetfulness, incoordination, altered handwriting and speech, and subsequently, chorea. Autopsy showed atrophy of the basal ganglia. Their mother died at the age of 55 years of a similar disorder. Which of the following best approximates the risk of this woman’s son for developing the disorder?

A 3-year-old girl is brought to the physician because of a 1 -year history of short stature. She has no history of major medical illness. She is below the 3rd percentile for height and at the 10th percentile for weight. Physical examination shows coarse facial features and contractures of the large joints. X-rays show dysostosis multiplex. Plasma lysosomal enzyme analysis shows increased (β-hexosaminidase, (β-glucuronidase, (β-galactosidase, and α-fucosidase activities. Which of the following mechanisms is the most likely cause of the lysosomal enzyme findings in this patient?

A 26-year-old man comes to the physician because of a 1-week history of temperatures to 38.3°C (101°F), chills, and chest and back pain. Two weeks ago, he returned from a trip to Costa Rica, where he had been performing ecologic studies of bats in their cave habitats. He reports exposure to bat urine and feces during his studies. Today, his temperature is 38.1°C (100.6°F). Physical examination shows no other abnormalities. A complete blood count and serum chemistry studies are within the reference ranges. A chest x-ray shows bilateral reticulonodular infiltrates. The virulence of the most likely infectious agent in this patient depends on which of the following?

A researcher in a pharmaceutical company designs a new protease inhibitor that inhibits replication of HIV in T lymphocytes in culture. In subsequent assays, which of the following findings is most likely to indicate that the compound is working specifically as a protease inhibitor?

A 73-year-old man with polymicrobial sepsis begins treatment with a variety of antibiotics, including gentamicin (current dose indicated in table). Three days later, serum gentamicin concentrations are 8.8 pg/mL (peak) and 2.5 pg/mL (trough). Which of the following dose regimens is most appropriate for achieving a peak serum gentamicin concentration between 4 and 10 pg/mL and a trough concentration of less than 2 pg/mL?

A 68-year-old woman with a 20-year history of hypertension is brought to the emergency department 30 minutes after the sudden onset of right-sided weakness. Her speech is dysarthric. Physical examination shows drooping of the right side of the face. Visual field testing shows no deficits. Muscle strength is 4/5 in the right upper extremity and 3/5 in the right lower extremity. Deep tendon reflexes are 2+ in the upper extremities and left lower extremity and 3+ in the right lower extremity. Sensation is intact throughout. Babinski sign is present on the right. Mental status examination shows no abnormalities. Which of the following is the most likely cause of this patient’s condition?

A 55-year-old man comes to the physician because of a 2-month history of hoarseness and difficulty swallowing. He underwent an operation to resect a lobe of his lung because of lung cancer 1 year ago. Physical examination shows ptosis of the left eyelid and miosis of the left pupil. There is diminished flushing and sweating on the left half of the face. This patient most likely has disordered function of neurons at which of the following labeled locations in the photograph of a cross section of the spinal cord?

A 31-year-old woman is brought to the emergency department by her husband because of difficulty breathing and severe muscle weakness for 10 minutes. She has a 3-year history of myasthenia gravis treated with neostigmine. The husband reports that she doubled her dosage 2 days ago because she was feeling extraordinarily weak, but her weakness has increased since then. Which of the following events is the most likely cause of the increased muscle weakness in this patient?

In a 3-week-old knockout mouse, a leg bone reaches only half the length of that of a similar-aged wild-type mouse. The epiphyseal plates in the bone of the transgenic animal are significantly narrower than in the bone of the wild-type animal. The knockout mouse most likely has a deficiency of which of the following?

A 60-year-old woman dies of a myocardial infarction. Incidental findings on examination at autopsy include multiple 0.5- to 1-cm stool-filled outpouchings of the sigmoid colon alongside the taeniae coli. The outpouchings protrude through the muscularis propria. Microscopic examination of a lesion shows a thin wall consisting of attenuated colonic mucosa and submucosa. Which of the following mechanisms best explains the formation of these lesions in the colon?

One hundred patients discharged from the hospital with a diagnosis of proximal deep venous thrombosis were followed for the development of venous ulceration for up to 8 years (DVT group). They were compared to a group of 200 patients who were discharged from the hospital with a diagnosis of pneumonia (the control group). At the end of 5 years, 25 patients in the DVT group and 10 patients in the control group developed venous ulceration. Which of the following is the attributable (excess) risk per one hundred patients for development of venous ulceration following deep venous thrombosis over 5 years?

A 53-year-old man comes to the physician for a follow-up examination. He began antibiotic therapy 1 month ago for acute bacterial pneumonia. At the time of diagnosis, a chest x-ray showed patchy pneumonic consolidation and a 2.5-cm peripheral nodular lesion in the right upper lobe. His symptoms have since resolved, and an x-ray today shows absence of the pneumonic consolidation. However, the lesion is still present. A PPD skin test is nonreactive. A wedge resection is done by thoracoscopy. Histologic examination of the resected tissue shows a solid, well-circumscribed nodule composed predominantly of mature cartilage admixed with small amounts of fibrous tissue and occasional clefts lined by benign respiratory epithelium. Which of the following best describes this patient’s pulmonary lesion?

A 62-year-old man with hypertension comes to the physician because of a 10-day history of fatigue and shortness of breath. His temperature is 37.4°C (99.4°F), pulse is 102/min, respirations are 18/min, and blood pressure is 110/70 mm Hg. Pulmonary examination shows diffusely decreased breath sounds and a prolonged expiratory phase. Cardiac examination shows distant heart sounds. There is 1+ pretibial edema of the lower extremities. Pulmonary function testing shows:

Which of the following is the most likely diagnosis?

A 57-year old man has a hemoglobin concentration of 18.5 g/dL. A peripheral blood smear is shown. These findings are most consistent with which of the following disorders?

A previously healthy 32-year-old man is brought to the emergency department because of a 1-day history of intermittent flashing spots and blurred vision, vomiting, confusion, and difficulty walking. He is a painter and says that yesterday he cleaned up a spilled bottle of paint thinner. Ophthalmologic examination shows dilated pupils with hyperemia of the optic disc and retinal edema. Physical examination shows tachypnea. Serum studies show an anion gap metabolic acidosis. The most appropriate pharmacotherapy for this patient is most likely to inhibit the activity of which of the following?

A 2 1/2-year-old boy is admitted to the hospital because of generalized weakness, repeated episodes of vomiting, and coma after several days of reduced food intake because of a minor febrile illness. He is treated successfully with intravenous glucose. After 13 hours of fasting when the child is well, his serum glucose, [3-hydroxybutyrate, and free carnitine concentrations decrease markedly, and serum concentrations of long-chain acylcarnitines increase. Triglycerides containing only medium-chain fatty acids are fed, and the serum (3-hydroxybutyrate concentration increases to the reference range. Which of the following disorders of fatty acid metabolism is the most likely diagnosis?

A 35-year-old woman is brought to the emergency department comatose after she sustained multiple injuries in a motor vehicle collision. During the next few days, she develops sepsis and respiratory insufficiency, and then she dies. A photomicrograph of her lungs obtained at autopsy is shown. If this patient had recovered, regeneration of the alveolar epithelium would have been accomplished via hyperplasia of which of the following cell types?

A 55-year-old man has a cough, hemoptysis, and dyspnea. He has smoked 2 packs of cigarettes daily for the past 30 years, distention of sublingual veins, and edema of the upper extremities. Which of the following additional findings is most likely to

A 24-year-old man who is serving overseas in the US Armed Forces is brought to a medical unit 30 minutes after sustaining multiple injuries caused by an explosion that forcibly ejected him from the vehicle he was driving. On arrival, he is conscious and hemodynamically stable. His respirations are 30/min. Physical examination shows visible shrapnel protruding from the lower sternum. Which of the following structures within the pericardial sac is most likely damaged in this patient?

A 25-year-old primigravid woman at 12 weeks’ gestation comes to the physician 1 hour after she passed a small amount of tissue vaginally at home. Gross examination of this tissue shows an obvious fetus. Microscopic examination of tissue obtained via dilatation and curettage shows chorionic villi with focal edema and trophoblastic proliferation. Which of the following is the most likely diagnosis?

A 42-year-old woman comes to the physician because of a 3-week history of numbness of the fingers on the left hand. Neurologic examination shows loss of touch graphesthesia and loss of two-point discrimination in the left hand. This patient most likely has a lesion in which of the following locations of the hemispheres shown?

A 35-year-old woman with sickle cell trait is brought to the emergency department because of severe left flank pain for 1 hour. She has a history of frequent headaches. Her blood pressure is 150/90 mm Hg. Pressure on the costophrenic angle causes pain. Urinalysis shows a few RBCs and numerous neutrophils. A CT scan of the abdomen shows obstruction and dilation of the left ureter and blunting of several renal papillary pyramids. Which of the following is the most likely diagnosis?

Which of the following best explains why deoxygenated blood can carry more carbon dioxide for a given Pco2than oxygenated blood?

An 80-year-old man comes to the physician because of bleeding gums and bruises under his skin. He lives by himself and follows a diet low in vegetables and fruits. His prothrombin time is normal. Which of the following enzymes is most likely compromised in this clinical scenario?

A 35-year-old homeless man is brought to the emergency department by police after they found him slumped on a bench. His pulse is 40/min, respirations are 10/min, and blood pressure is 100/60 mm Hg. He is stuporous but can be aroused when shaken mildly. Physical examination shows constricted pupils. This patient is most likely abusing which of the following substances?

A 50-year-old man is brought to the physician 2 days after the onset of double vision and drowsiness. Three weeks ago, he began using over-the-counter cimetidine for dyspepsia. He has epilepsy treated with phenytoin for the past 2 years. Physical examination shows nystagmus and an ataxic gait. Which of the following effects of cimetidine on phenytoin is the most likely cause of the adverse effects in this patient?

An investigator is conducting a study of the efficacy of certain vitamins in helping to prevent heart disease in women. Eight thousand women, 45 years of age or older, are enrolled in the study. Two thousand women receive vitamin C only, 2000 receive vitamin E only, 2000 receive both vitamins C and E, and 2000 receive a placebo. The investigator finds that the vitamins are ineffective in helping to prevent heart disease. Which of the following best describes the study design used in this clinical trial?

A 52-year-old man comes to the physician because of a 5-day history of headaches and muscle weakness. His blood pressure is 175/95 mm Hg. Physical examination shows no other abnormalities. Laboratory studies show:

Plasma renin activity is undetectable. Which of the following is the most likely cause of this patient’s hypertension?

A 21-year-old man comes to the physician because of a lump in his scrotum for 3 months. Physical examination shows a 1-cm nontender nodule in the right scrotum. Transillumination shows a solid, noncystic structure. An operation to remove the testis is done. After incision of the skin and subcutaneous tissue, the next fascial layer to be incised in this patient is a direct extension of which of the following abdominal layers?

A 14-year-old boy is brought to the physician’s office because of decreased appetite and abdominal pain over the past 3 weeks. His mother says that during the same time he has withdrawn from everyone and sleeps constantly. He describes his symptoms vaguely. Physical examination is normal. During further history-taking, it is most critical for the physician to obtain information about which of the following?

A 22-year-old man is brought to the emergency department 1 hour after being involved in a motor vehicle collision. Physical examination shows deep lacerations to the right lower extremity. Which of the following functional capabilities of the involved muscles will be decreased by fibrotic scar formation at the sites of injury?

An 8-year-old girl is brought to the physician by her mother 1 hour after her cat scratched her on her right arm. The mother says that the patient developed bright red streaks along her arm within minutes of being scratched. The scratches were painful, and the patient was crying when she showed the injury to her mother. Examination of the right forearm shows the surface linear streaks with intact skin, but there is no blood. The appearance of the red streaks most likely indicated which of the following host responses to this injury?

50. A study is conducted to assess the prevalence and incidence of obesity in a group of middle-aged men. A total of 900 men between the ages of 40 and 50 years are chosen to participate. The table shows the number of participants at baseline and at the follow-up study 5 years later for each BMI range.

The prevalence of obesity in this study population after 5 years is which of the following?