A 37-year-old woman comes to the physician for a follow-up examination 3 months after receiving a kidney transplant from a cadaver donor. She feels well, and her condition has been stable since the transplant. She receives standard immunosuppressive medications. Her temperature is 37°C (98.6°F), pulse is 84/min, respirations are 14/min, and blood pressure is 150/90 mm Hg. Physical examination shows a well-healed surgical scar over the lower abdomen. Serum studies show a creatinine concentration of 2 mg/dL; baseline creatinine concentration was 1.4 mg/dL 1 week post transplant, and 2 weeks ago. Serum concentrations of the immunosuppressive drugs are in the low therapeutic range. Examination of a renal biopsy specimen shows lymphocytes in the tubules and arterial walls. Which of the following best explains these findings?

A 63-year-old man with alcoholism is diagnosed with hepatic encephalopathy. Treatment with lactulose therapy via nasogastric tube is begun. The effectiveness of this intervention requires which of the following mechanisms?

A 5-month-old boy is brought to the physician by his parents because of a 1 -week history of weakness. His parents are first cousins. Physical examination shows pallor, jaundice, and hepatosplenomegaly. His hemoglobin concentration is 6 g/dL, hematocrit is 19%, and serum bilirubin concentration is 4.2 mg/dL (mostly indirect). A photomicrograph of a peripheral blood smear is shown. Hemoglobin (Hb) electrophoresis shows HbF, no HbA, and an increased concentration of HbA2. Which of the following is the most likely molecular cause of this patient’s condition?

A 43-year-old woman, gravida 2, para 1, at 10 weeks’ gestation comes to the physician for an initial prenatal visit. Physical examination shows a uterus consistent in size with a 10-week gestation. This patient is at increased risk for a child with Down syndrome if she has which of the following sets of ultrasound and serum findings?

A 62-year-old man comes to the physician because of a swollen, painful left great toe that awakened him from sleep this morning. Examination of the toe shows erythema, swelling, and exquisite tenderness. Laboratory studies show hyperuricemia. Treatment with colchicine resolves the acute symptoms. Long-term therapy with allopurinol is begun. This treatment results in decreased urate biosynthesis. A diagram of purine synthesis is shown. Which of the following labeled steps is directly inhibited by allopurinol as a result of this therapy?

In a sample of 100 individuals, the mean leukocyte count is 7500/mm3, with a standard deviation of 1000/mm3. Assuming that the leukocyte counts in this population follow a normal (gaussian) distribution, which of the following best represents the percentage of time that a randomly selected individual will have a total leukocyte count lower than 5500/mm3?

A 7-day-old female newborn is brought to the physician because blood has been oozing from the umbilical area for more than 24 hours. She was born at home, has had no previous medical treatment, and has been breast-fed since birth. Which of the following biochemical reactions is most likely defective in this patient?

A 35-year-old woman comes to the physician in the spring because of a 2-week history of tearing and itching of her eyes. She has a 10-year history of similar symptoms during this time of year. She attributes her condition to an allergy to pollen and grasses. Her symptoms improve when she takes an over-the-counter antihistamine. The antihistamine therapy most likely affects which of the following aspects of the host response in this patient?

A 43-year-old man comes to the emergency department because of a 1-year history of low back pain. Before the examination, the patient says, “My physician is arrogant and insensitive. He never returns my phone calls, I always have to wait forever to be seen, the tests he orders are painful and unnecessary, and he can never tell me what is causing my back pain or how to treat it.” Which of the following is the most appropriate response by the emergency department physician about this patient’s complaints?

A 39-year-old woman with type 1 diabetes mellitus comes to the physician because of episodes of fainting during the past 3 weeks. The patient’s insulin monitoring has shown that the episodes occur when she becomes hypoglycemic. In the past, her hypoglycemic episodes were characterized by increased sweating, heart rate, and shaking of her hands, but now she loses consciousness without warning. Current medications are insulin, lisinopril, and simvastatin. Her pulse is 72/min, and blood pressure is 128/70 mm Hg. Physical examination shows no abnormalities. It is most appropriate for this patient to receive an injection of a drug with which of the following mechanisms of action during these episodes?

A 3-year-old boy is brought to the emergency department by his mother 1 hour after having a generalized tonic-clonic seizure. He has had frequent vomiting and progressive stupor during the past 24 hours. His mother says that she gave him aspirin 2 days ago because of a temperature of 39.5°C (103.1 °F). Physical examination shows hepatomegaly with no jaundice. Serum studies show an increased ammonia concentration, and increased AST and ALT activities. Dysfunction of which of the following is the most likely cause of this patient’s disorder?

Lysosomes present in hepatocytes of patients with mucolipidosis II (l-cell disease) contain abnormal enzyme activities resulting from an inability of these cells to do which of the following?

A woman who weighs 70 kg (154 lb) is participating in a research study. Her hematocrit is 40%, and her plasma volume is 3 L. The subject’s total blood volume (in L) is closest to which of the following?

A 42-year-old man comes to the physician for an examination prior to beginning an exercise program at a local health club. He has smoked 1 pack of cigarettes daily for 20 years. He is 183 cm (6 ft) tall and weighs 70 kg (155 lb); BMI is 21 kg/m2. His blood pressure is 130/80 mm Hg. Physical examination shows no other abnormalities. Serum studies show:

Which of the following defects is the most likely cause of this patient’s increased serum LDL-cholesterol concentration?

A 36-year-old woman comes to the physician for a follow-up examination 1 week after being diagnosed with severe hypertension. Her blood pressure is 180/120 mm Hg. Physical examination shows no other abnormalities. A CT scan of the abdomen shows a renal artery aneurysm. A renal angiogram obtained from a femoral approach is shown. Which of the following is the most likely cause of these findings?

A 45-year-old man who works in a government building is brought to the emergency department because of a 2-hour history of severe shortness of breath with obvious bronchoconstriction and cough productive of copious secretions. He also has had nausea, vomiting, and diarrhea. At least 20 other people in his office building were affected by similar symptoms at approximately the same time. Two of these coworkers died on the way to the hospital. Only a few of the affected employees ate together in the government cafeteria that day. His respirations are 36/min. Physical examination shows excessive lacrimation. Which of the following is the most likely cause of the sudden disease outbreak?

A 65-year-old man comes to the physician 2 weeks after noticing a lesion on his neck. He is an avid golfer, playing. Examination of the neck shows a 10-mm, pearly pink, raised nodule. This patient’s condition most and he always wears a hat but does not always use sunscreen while likely originated in which of the following?

A 45-year-old man is brought to the physician by his parents because he is reclusive, has “weird ideas,” and still wants to live at home. He is dressed in several layers of clothes. During the interview, he is cooperative but he has poor eye contact and seems uninterested in the interview. He says, “I believe some people can read other people’s minds. I carry these crystals to help me realize self-actualization.” He has no delusions or hallucinations. This patient most likely has which of the following personality disorders?

A 34-year-old woman comes to the office because of a 2-day history of a full-body rash. The rash is not itchy, and she has had no other symptoms. She has a staphylococcal abscess on her right buttock for which she has been taking trimethoprim-sulfamethoxazole for the past week. She last had sexual intercourse 2 years ago. She currently is menstruating. She recently adopted a cat and changed laundry detergents to a dye-free variety. She has no history of tick bites. Her temperature is 37.1 °C (98.8°F), pulse is 80/min, respirations are 16/min, and blood pressure is 130/85 mm Hg. A photograph of the patient’s right upper extremity is shown; there are similar findings over the trunk and remaining extremities, including the hands and feet. The mucous membranes appear intact. Examination of the buttocks shows a healed abscess; the skin has closed, and there is no surrounding cellulitis. Which of the following is the most likely cause of this patient’s condition?

A 42-year-old man comes to the physician because of chronic abdominal pain for 3 months. He describes his symptom as boring epigastric pain that is occasionally exacerbated by eating. He is an investment banker and describes his job as extremely stressful. Use of an over-the-counter histaminergic (H2)-receptor antagonist has mixed results. Vital signs are normal. Physical examination and upper endoscopy show no abnormalities. Which of the following is the most likely diagnosis?

An investigator is studying a tumor cell line in an experimental animal model in which the expression of class I MHC is completely inhibited. The cell line is assayed as a target for cell-mediated immune response by CD8+ T lymphocytes, CD4+ T lymphocytes, or natural killer cells. Which of the following sets of findings is most likely (+ = killing; – = no)

Which of the following curves best describes variation of follicle-stimulating hormone concentration during the menstrual cycle?

A 30-year-old woman has polyhydramnios at 25 weeks’ gestation. The fetus has an anatomically normal esophagus. Which of the following abnormalities is the most likely cause of the polyhydramnios?

The formula shown describes the rate of metabolism of Drug X where v is the rate of metabolism, Vmax is the maximal rate of metabolism, and Michaelis constant [K J is the plasma concentration at one half the maximum rate of metabolism. If the concentration of Drug X is 100 times greater than the Km of the metabolic enzyme for Drug X, which of the following conclusions is most appropriate?

An investigator studying type 2 diabetes discovers an inhibitor of uncoupling protein-2 that stimulates insulin secretion from mouse pancreatic islet cells. This inhibitor most likely increases insulin secretion by which of the following actions?

A plasmid has acquired a mutation that prevents it from replicating in bacteria. This mutation most likely affects which of the following regions within the plasmid?

A 30-year-old man comes to the office because of a 1-week history of nausea and yellowing of the whites of his eyes. He has no history of serious illness and takes no medications. Vital signs are within normal limits. Abdominal examination shows hepatomegaly; there is tenderness to palpation over the right upper quadrant. Serologic testing is positive for hepatitis A virus IgM antibodies. A high-power photomicrograph of a liver biopsy specimen obtained from a patient with a similar condition is shown. Which of the following is the most likely mechanism of hepatocyte cell death in this patient?

An 82-year-old woman is admitted to the hospital for treatment of a small right pleural effusion. Physical examination shows dullness to percussion at the level of the 7th rib and below on the right. A thoracentesis is done. The patient is sitting up, supported by leaning against a bedside table. After preparing the skin and delivering a local anesthetic, into which of the following locations on the right is it most appropriate to insert the catheter?

A 56-year-old man with alcoholism comes to the physician because of a 2-month history of increasingly severe stomach pain and increased volumes of foul-smelling stool; he also has had a 9-kg (20-lb) weight loss during this period. He has a history of multiple visits to the emergency department because of severe abdominal pain. He has consumed one bottle of red wine daily for 5 years. His temperature is 37°C (98.6°F). Physical examination shows epigastric tenderness. His fasting serum glucose concentration is 150 mg/dL. ACT scan of the abdomen shows pancreatic calcifications. The most likely cause of this patient’s current symptoms is a decrease in which of the following?

A 45-year-old woman with chronic hepatitis C comes to the physician because of a 3-week history of fatigue and joint pain. Her temperature is 37.5°C (99.5°F), pulse is 88/min, and blood pressure is 155/75 mm Hg. Physical examination shows the findings in the photograph and hepatosplenomegaly. Serum studies are most likely to show an increased amount of which of the following in this patient?

A 55-year-old woman comes to the physician because of a 3-day history of persistent right shoulder pain. She began a weight-training program 6 weeks ago. She says that the pain intensified after she increased the amount of weight that she had been lifting above her head. She rates the pain as 8 on a 10-point scale. Examination of the right shoulder shows point tenderness just lateral to the acromion, over the humeral head. Passive motion of the shoulder is full. Pain is reproduced with resisted abduction of the shoulder when the shoulder is abducted 90 degrees and the arm is giving the “thumbs down” sign. Sensation is intact over the right upper extremity. Which of the following tendons is most likely injured in this patient?

A 25-year-old woman comes to the physician 2 days after noticing a mass in her right axilla. She also has a 1-week history of malaise, headaches, and night sweats. The patient says that she recently adopted a kitten and has sustained several bite and scratch marks. Her temperature is 37.8°C (100°F). Physical examination shows edema and tenderness of the right axillary lymph node. The skin over the node is erythematous, tough, and warm. There are scratches and bite marks of various ages over the upper extremities and hands. The result of an indirect fluorescent antibody test for Bartonella henselae is positive. A biopsy specimen of this lymph node is most likely to show which of the following histologic patterns?

A 70-year-old man comes to the physician with his wife because of a 6-month history of abnormal behavior during sleep. His wife says, “He suddenly punches at the air and yells as if he were acting out his dreams, but he doesn’t wake up.” As a result of his agitation, he has fallen on the floor several times. Neurologic examination shows no abnormalities. Which of the following additional findings is most likely in this patient?

A 35-year-old woman comes to the emergency department because of abdominal cramps, nausea, and vomiting for 8 hours. Her pulse is 106/min and regular, and blood pressure is 140/96 mm Hg. Physical examination shows rhinorrhea, excessive lacrimation, and diaphoresis. There is piloerection over most of the skin. The pupils are dilated, equal in size, and responsive to direct and indirect light. There is a resting tremor involving both upper extremities. During the examination, the patient is restless and yawns constantly. This patient is most likely experiencing withdrawal symptoms from which of the following substances?

A 45-year-old man with mild hypertension uses a nasal spray for allergic rhinitis and nasal congestion. Four days later, the spray no longer relieves his symptoms and his blood pressure is increased. Which of the following best describes the action of this drug?

A 19-year-old man is admitted to the hospital following a motor vehicle collision. Physical examination shows a penetrating wound to the right cerebral cortex with complete paralysis of the left lower extremity, fracture of the right mid humerus with severing of the radial nerve, and a fracture of the right tibia. Treatment includes cast immobilization of the right upper extremity and right knee and ankle. After 10 weeks, the casts are scheduled to be removed from the right upper and lower extremities. At this point, the deep tendon reflex is most likely to be strongest in which of the following locations in this patient?

The solid curve represents the normal oxygen-hemoglobin dissociation curve. The dashed curve is consistent with an increase in which of the following?

An 18-year-old man has a 1-hour history of wheezing, chest tightness, and shortness of breath. He weighs 60 kg (132 lb). Minute ventilation is 14 L/min (N=5-10 L/min). Which of the following sets of arterial blood gas findings is most likely present in this patient?

A 60-year-old man has two-pillow orthopnea, severe dyspnea, and edema of the lower extremities. The onset of these symptoms was preceded by an episode of prolonged substernal chest pain 5 days ago. Which of the following additional findings on examination of the neck is most consistent with these findings?

A 36-year-old man who is seropositive for HIV has had fever and shortness of breath for 2 days. An x-ray of the chest shows a diffuse interstitial infiltrate. A lung biopsy is shown. Which of the following organisms is most likely involved?

In an experiment on ion transport in epithelial cells isolated from various regions of the nephron, hydrochlorothiazide inhibits Na+entry into one group of cells. These cells were most likely obtained from which of the following regions?

A 28-year-old woman, gravida 4, para 0, aborta 3, with systemic lupus erythematosus comes to the physician at 12 weeks’ gestation for an initial prenatal examination. She is concerned that she will not be able to carry her current pregnancy to term. The presence of which of the following is most likely increasing the risk for complications during pregnancy in this patient?

A 58-year-old woman is brought to the emergency department because of a 2-hour history of shortness of breath and chest pain that radiates to her back between the shoulder blades. Her respirations are 28/min. Physical examination shows diaphoresis. An ECG shows no abnormalities. Coronary angiography shows occlusion of the marginal branch of the left anterior descending coronary artery. A percutaneous coronary revascularization is done. Subsequent to the stent’s placement, her serum concentrations of myocardial creatine kinase (CK-MB) and troponin I are increased. Which of the following mechanisms best explains these laboratory findings?

A previously healthy 43-year-old man comes to the physician because of a 1-week history of fever; vague, migratory abdominal pain; and generalized muscle pain and weakness. He has no history of a similar illness. His temperature is 38.2°C (100.8°F), pulse is 78/min, respirations are 16/min, and blood pressure is 150/94 mm Hg. Pulmonary examination shows no abnormalities. Abdominal examination shows diffuse tenderness with no organomegaly. There is generalized muscle weakness and tenderness to palpation of various muscle groups. Laboratory studies show:

Blood cultures are negative. Examination of a muscle biopsy specimen from this patient shows segmental transmural necrotizing arteritis. Which of the following is the most likely diagnosis?

The breakdown of dipeptides and tripeptides to free amino acids takes place primarily in which of the following areas in the gastrointestinal tract?

A 29-year-old man has a left testicular mass. A frozen section obtained during a planned orchiectomy shows a seminoma. Which of the following provides the greatest risk factor associated with this condition?

An investigator working in a large health care system wishes to determine the attitude of physicians toward drug screening in the workplace. To collect the information,
physicians in the health system are invited to respond to an e-mail survey that is distributed on the health system’s network. Which of the following most closely describes this type of sampling technique?

A 45-year-old man has shortness of breath. He has never smoked cigarettes. There is no evidence of cardiac disease. X-rays of the chest show bullous air spaces in the lower lobes. The pathophysiologic basis of this process is most likely to be a deficiency of which of the following?

A study is conducted on patients with asthma to compare a new asthma treatment with a placebo. After 12 weeks of treatment, the mean (± standard error of the mean) scores are 2.8 ±0.1 in the treated group (n = 103) and 3.1 ± 0.1 in the placebo group (n = 100). The p-value is 0.035. Which of the following best describes the meaning of the p-value?

A 25-year-old woman comes to the physician because of a 9-month history of fatigue, excessive sweating, heat intolerance, palpitations, and nervousness; she has had a 9-kg (20-lb) weight loss during this period. Her pulse is 105/min. Physical examination shows moist skin and a goiter. Which of the following is most likely decreased in this patient?