A 30-year-old woman and her 35-year-old husband come to the physician for genetic counseling prior to conception. They have a 2-year-old daughter with an isolated ventricular septal defect. The wife’s sister had a heart defect, for which she underwent operative repair. Previous evaluation of the couple, including echocardiography, showed no abnormalities. Which of the following best represents this couple’s risk for having another child with a congenital heart defect?

A 50-year-old woman comes to the physician because of progressive shortness of breath during the past 2 years. Her respirations are 20/min. Physical examination shows cyanosis and ankle edema. Her pulmonary artery pressure, pulmonary vascular resistance, and right atrial pressure are increased; her pulmonary capillary wedge pressure is 9.3 mm Hg (N=8-16). Her ventilation improves when inhaled nitric oxide is administered. Treatment with oral bosentan is begun for long-term therapy. Which of the following mediators of pulmonary resistance in this patient will most likely be antagonized by this drug?

A 40-year-old woman comes to the physician because of pain of her hands, wrists, and knees for 2 weeks. Physical examination shows swelling, tenderness, and warmth of the proximal interphalangeal, wrist, and knee joints. Laboratory studies show an increased erythrocyte sedimentation rate and normochromic, normocytic anemia. A test result for rheumatoid factor is positive. Which of the following sets of findings in synovial fluid obtained from the knee joint is most likely in this patient?

A 57-year-old woman comes to the physician 3 days after she found a lump in her left breast on self-examination. Physical examination shows a 1.3-cm mass in the left breast. Microscopic examination of a biopsy specimen of the mass shows carcinoma. It is most appropriate for the physician to consider which of the following when grading the carcinoma?

A 35-year-old man is brought to the physician by staff of the group home where he resides because of worsening behavior for 2 weeks. During the interview, he tells the physician that he believes the CIA is spying on him through his television set. He then reports hearing voices in the hall outside the examination room and states that the CIA now plans to kill him. He appears disheveled with unkempt hair and poor hygiene. He has difficulty answering the physician’s questions because he seems to be listening to internal stimuli. Mental status examination of the patient is most likely to show which of the following findings?

A 65-year-old woman comes to the emergency department because of a 4-hour history of vomiting bright red blood; she also has had dizziness and nausea during this period. Her pulse is 140/min, and blood pressure is 70/30 mm Hg. Physical examination shows pale, clammy skin, diaphoresis, and decreased capillary refill time. A diagnosis of hypovolemic shock is made. Placement of a catheter in the internal jugular vein for blood transfusions is planned. Improper insertion of the catheter is most likely to result in damage to which of the following sets of underlying structures?

A 42-year-old man comes to the physician because of progressive weakness of his hands during the past 10 months. Physical examination shows atrophy of the hand muscles with fasciculations. There are also fasciculations of the tongue and trapezius muscles. Electromyography confirms the diagnosis of amyotrophic lateral sclerosis. Which of the following initial statements by the physician is most appropriate?

A 68-year-old man with Parkinson disease is being treated with levodopa and carbidopa. He is doing well and has few adverse effects. Concurrent therapy with levodopa and carbidopa is useful because of which of the following characteristics of carbidopa?

A 25-year-old woman, gravida 2, para 2, comes to the physician because of a painful lump in the right vulva. Her last menstrual period was 1 week ago. She does not recall any recent trauma and has had no prior vaginal infections. Examination shows an acutely tender, 2.5-cm mass that is located near the vaginal orifice posteriorly and distends the labia majora. It appears to point vaginally. Which of the following is the most likely diagnosis?

A 34-year-old man is brought to the emergency department semiconscious and combative. In addition to sedation, a short-acting neuromuscular blocking agent is administered for intubation to prevent aspiration. Within a few seconds after administration of the drug, he has transient muscle fasciculations in his face; he develops generalized paralysis within 1 minute. Forty-five minutes after completion of the procedure, he is still paralyzed. A genetic abnormality of which of the following enzymes is the most likely cause of his unusually slow recovery from paralysis?

The table shows serum osmolality, urine osmolality, and urine flow rate measured at 30-minute intervals in a 30-year-old man. Which of the following substances was most likely administered at time 0?

A healthy 27-year-old woman consumes a turkey sandwich, a cup of sweetened yogurt, an apple, and three cookies for lunch. After lunch, she returns to working at a computer. Two hours later, she drinks a 16-ounce bottle of cola sweetened with high fructose corn syrup and sucrose. The activity of which of the following enzymes is most likely increased in this patient’s liver?

A 19-year-old man who is a soldier in the US Army sustains a traumatic brain injury from the detonation of an improvised explosive device while on patrol in the Middle East. This patient is at increased risk for additional neuronal apoptosis caused by diffusion of which of the following substances from the cerebral capillaries to the brain parenchyma?

A 69-year-old woman comes to the physician because she has had weakness of her left leg since awakening that morning. Physical examination shows weakness of the extremity. A Babinski sign is present on the left. Sensory testing shows decreased somatic sensation in the left foot, agraphesthesia on the plantar surfaces of the toes, and decreased position sense in the toes. An MRI of the brain shows an edematous area in the cerebral cortex of the right hemisphere. The most likely cause of this condition is a lesion located at which of the following labeled areas in the photographs of normal brains shown?

A 45-year-old man comes to the physician because of a 2-week history of pain of his left testis. Six weeks ago, he had a vasectomy. Physical examination shows a bead-like mass of the left testis. Excision of the mass is done. Microscopic examination of the mass shows sheets of extravasated spermatozoa engulfed by histiocytes, many with prominent enlarged nuclei. This patient’s lesion is most likely the result of which of the following processes?

A 75-year-old man is found to have an 8-cm mass in the head of the pancreas that is encasing and markedly narrowing the inferior vena cava. Blood from this patient’s lower extremities is most likely returning to the superior vena cava from which of the following veins?

The following data about cancer prevalence and mortality are collected in a small city for a calendar year:

Which of the following is the period prevalence of ovarian cancer in women in this city

A 16-year-old boy is brought to the emergency department because of a 3-day history of episodes of sharp chest pain on the left that lasts for a few seconds. When the patient is asked to indicate the location of the pain, he points to the 4th rib on the left. The pain is not associated with change in position, and it does not radiate. There is no history of trauma. The patient appears anxious. His pulse is 90/min and regular. The left anteromedial area of the 4th rib is tender to palpation. Cardiac and pulmonary examinations show no abnormalities. Which of the following is the most likely diagnosis?

A 22-year-old woman comes to the physician for a follow-up examination. One year ago, she was diagnosed with a pulmonary embolism. Two years ago, she delivered a female stillborn at 23 weeks’ gestation. Physical examination today shows no abnormalities. Laboratory studies show a platelet count of 250,000/mm3, a prothrombin time within the reference range, and an increased partial thromboplastin time. The findings in this patient are most consistent with which of the following conditions?

A married couple and their 12-year-old son come to the emergency department because of a 2-hour history of nausea, vomiting, and diarrhea. They all ate lunch at a company picnic 6 hours ago. The physician suspects staphylococcal food poisoning and notifies the local health department. The health department contacts other picnic attendees to collect data on which foods they consumed at the event. Based on the investigation, ice cream is suspected as the source of the toxin. Among those who ate the ice cream,
96 became ill and 24 did not experience symptoms. Among those who did not eat the ice cream, 3 became ill and 27 did not experience symptoms. Which of the following is the relative risk for illness in those who ate the ice cream compared with those who did not?

In a breast-fed infant, lipase has an integral role in the digestion of which of the following?

The newborn of a mother with poorly controlled diabetes mellitus has a convulsion and dies shortly after birth. Which of the following morphologic changes is most likely to be seen on autopsy?

A 55-year-old woman is brought to the emergency department by police 1 hour after she was found wandering around the city park at midnight, appearing confused. She told the police that she is a prominent physician and a member of the city council. She is unwashed, malodorous, and disheveled. She is 160 cm (5 ft 3 in) tall and weighs 55 kg (121 lb); BMI is 21 kg/m2. Her pulse is 82/min, and blood pressure is 110/82 mm Hg. Physical examination shows a broad-based gait and nystagmus. She is not oriented to person, place, or time, but she is pleasant and cooperative. Results of alcohol and drug screening are negative. An MRI of the brain is most likely to show atrophy of which of the following?

A 23-year-old woman at 32 weeks’ gestation comes to the emergency department because of a 1-day history of left flank pain and fever. Her temperature is 39.1 °C (102.3°F), pulse is 104/min, respirations are 14/min, and blood pressure is 120/72 mm Hg. Physical examination shows prominent tenderness over the left costovertebral angle. A photomicrograph of a renal biopsy specimen from a similar patient is shown. Which of the following is the most likely diagnosis?

A male newborn is delivered at term with a right-sided aortic arch. Physical examination shows full cheeks, low-set ears, and a small chin. Serum studies show a decreased calcium concentration. Which of the following is the most likely site of the malformations in this patient?

A 27-year-old man has the sudden onset of fever and shaking chills 2 weeks after returning from a trip to Africa. He has mild anemia. A peripheral blood smear is shown. He is treated with chloroquine followed by primaquine. Which of the following best explains the benefit of using primaquine in this patient?

A 56-year-old woman is brought to the emergency department because of progressive shortness of breath during the past month. Two weeks ago, she underwent coronary artery bypass grafting. Her respirations are 26/min. There is dullness to percussion at the left base of the chest. A chest x-ray shows substantial fluid in the left pleural cavity. Thoracentesis yields 1200 mL of pale, milky fluid that is identified as chyle. Which of the following procedures during the operation most likely produced the iatrogenic chylothorax?

A 58-year-old man comes to the physician because of a 2-week history of severe chest pain when climbing stairs. He does not have chest pain at rest. The diagnosis of angina pectoris is made. Nitroglycerin is prescribed for this patient because of which of the following mechanisms of action?

A 2-year-old boy is brought to the physician because of chronic bacterial respiratory infections since birth. He is currently asymptomatic. Physical examination shows no abnormalities. T- and B-lymphocyte counts and serum antibody concentrations are within the reference ranges. Natural killer cell count and function are normal. Analysis of cellular expression of human leukocyte antigen by flow cytometry shows absence of class I MHC-expressing cells. A diagnosis of bare lymphocyte syndrome, type I, is made. This patient most likely has mutations in the genes encoding which of the following?

A 46-year-old woman comes to the physician because of a 3-day history of pain and swelling of her left leg. One week ago, she underwent operative removal of several sebaceous cysts over the labia majora. Physical examination shows edema of the left lower extremity and purulent material draining from one of the operative incisions. This patient most likely has an infection that spread to which of the following groups of lymph nodes?

An analysis of patients admitted to a specific hospital finds that the risk for myocardial infarction is higher in men with chronic obstructive pulmonary disease (COPD) than in men without COPD (odds ratio 5.4, 95% confidence interval: 1.4-10.1). These results can most reasonably be generalized to which of the following populations?

Patients with hyperuricemia are most likely to have a deficiency of which of the following enzymes?

A 7-year-old girl is admitted to the hospital because of severe anemia. Hemolytic anemia with a probable defect in glycolytic energy production is diagnosed. Results of pyruvate kinase activity in erythrocyte lysates using varying concentrations of phosphoenolpyruvate are shown. Which of the following best explains these findings?

A 57-year-old woman comes to the emergency department because of a 7-week history of fever, night sweats, and nonproductive cough; she also has had a 6.8-kg (15-lb) weight loss during this period. She is currently receiving pharmacotherapy for Crohn disease but does not remember the name of the medication. Her temperature is 38.2°C (100.8°F), pulse is 90/min, respirations are 23/min, and blood pressure is 130/90 mm Hg. Amphoric breath sounds are heard over the right upper lung field. A chest x-ray is shown. This patient is most likely being treated with a monoclonal antibody targeted against which of the following?

A 38-year-old pregnant woman had genetic amniocentesis that showed a 46,XX karyotype in the cultured amniotic fluid cells. A newborn was delivered with normal male external genitalia, testes, and genital ducts. Which of the following is the most likely explanation?

A 43-year-old man with a 10-year history of alcoholism comes to the physician because of a change in skin color. The patient says that he has been taking two extra-strength acetaminophen tablets every 4 to 6 hours for the past 3 days for a severe headache. Physical examination shows jaundice. Laboratory studies show an increased prothrombin time and a markedly increased serum AST activity. Alteration in which of the following metabolites within hepatocytes is most likely associated with his illness?

A 68-year-old man comes to the emergency department in a mountain resort town with his wife because of a 1 -month history of shortness of breath and headaches. One month earlier, he retired and moved from his home at sea level to the resort town which is 9000 feet above sea level. His wife is asymptomatic. His respirations are 16/min. Laboratory studies show an erythrocyte count of 4 million/mm3. This patient most likely has a history of disease of which of the following organs?

An 18-year-old man with Crohn disease is admitted to the hospital because of a 1-day history of severe abdominal pain and intermittent bloody diarrhea. His temperature is 38°C (100.4°F), pulse is 98/min, and respirations are 18/min. Physical examination shows a draining anal fistula. Treatment with broad-spectrum antibiotics and prednisone, along with intravenous hydration and parenteral nutrition, is initiated. He recovers over the next 3 weeks. In addition to resolving the infection, the most likely mechanism of action of this pharmacotherapy is suppression of which of the following?

A 30-year-old man who is seropositive for HIV develops nausea, vomiting, watery diarrhea without blood, abdominal cramps, and a 2.3-kg (5-lb) weight loss over 10 days. A diagnosis is made by microscopic examination of stool. Which of the following is the most likely causal organism?

An experiment is designed to assay the secretions of chondrocytes obtained from the articular cartilage of osteoarthritic joints. Which of the following compounds is most likely to be found in decreased concentration in the secretions?

A 28-year-old man comes to the physician because of a 2-week history of light-headedness, mild chest pain, palpitations, and shortness of breath after exercising. He has no history of major medical illnesses. His temperature is 36.9°C (98.4°F), pulse is 72/min, respirations are 17/min, and blood pressure is 120/82 mm Hg. Cardiac examination shows a bounding point of maximal impulse that is shifted to the left. Echocardiography shows cardiomegaly and marked thickening of the ventricular septum. It is most appropriate for the initial therapy to increase which of the following in this patient?

A 2-year-old boy is brought to the physician because of a 1-week history of high-grade fever and rash. His temperature is 39.6°C (103.3°F), pulse is 144/min, and blood pressure is 122/76 mm Hg. Physical examination shows marked conjunctival injection and erythema and edema of the hands and feet. A photograph of the cheeks and mouth is shown. Echocardiography shows dilation of the proximal coronary arteries. Which of the following is the most likely diagnosis?

A 27-year-old woman comes to the physician 3 weeks after the onset of blurred vision in her right eye that has been improving during the past 5 days. She had a similar episode 1 year ago while working on a ranch in northeastern Arizona; the episode resolved in 2 weeks without treatment. She has no history of major medical illness. Ophthalmologic examination shows a right afferent pupillary defect. Visual acuity is 20/20 in the left eye and 20/200 in the right eye. Neurologic examination shows mild weakness of the lower two thirds of the right side of the face and a right pronator drift. There is mild dysmetria when she moves the left extremities. An MRI of the brain is shown; the arrows indicate multiple abnormalities. Which of the following is the most likely diagnosis?

In a clinical study of a molecular variant hypothesized to be related to schizophrenia, 200 subjects are examined for a particular single nucleotide polymorphism. The results are shown in the table.

If A is one allele and G is the other, which of the following is the frequency of allele A?

During a study of familial hypercholesterolemia, hepatocytes from an affected patient are extracted and analyzed. Results show that the LDL receptors are evenly distributed on the surface of the cells. The cells also bind LDL-cholesterol with normal affinity but cannot internalize it. The cells are shown to internalize transferrin. Based on these findings, which of the following is the most likely location of the causal mutation in this patient?

A previously healthy 18-year-old woman comes to the physician because of a 3-day history of pain with urination and urinary frequency and urgency. Physical examination shows mild tenderness over the suprapubic region. A urine culture grows an organism that is lactose fermenting and spot-indole test positive. The organism is resistant to ampicillin but sensitive to ceftriaxone. Which of the following is the most likely mechanism of antimicrobial resistance exhibited by this organism?

A 70-year-old woman comes to the physician because of an 8-month history of foul-smelling breath and pain before and after she swallows. Physical examination shows halitosis. Two views from a barium swallow are shown; the arrow indicates a diverticulum. This abnormality is most likely located between which of the following muscles?

A 46-year-old woman with systemic lupus erythematosus has had chest pain and fever for 2 days. Temperature is 38.3°C (101°F), pulse is 118/min, and blood pressure is 96/68 mm Hg. Heart sounds are distant. An ECG shows low voltage. Which of the following types of pulses is most likely in this patient?

A 12-year-old boy is brought to the physician by his mother because of a persistent rash around his nose and mouth for 4 months. He also has had a decreased appetite and an unintentional 4.5-kg (10-lb) weight loss during the past 3 months. His mother states, “The rash developed shortly after he started at his new school. I wonder if he keeps getting into something. I’ve tried hydrocortisone cream, but it didn’t work.” She adds, “And now his grades are falling, and he’s not eating as much as he used to. I hope he’s not depressed because of the rash.” The rash began as mild redness and then became dry and started to flake. The patient says there is no pain or discomfort with the rash. Physical examination shows injection of both conjunctivae, an eczematous eruption extending interiorly from the nasolabial fold to the upper lip, and an erythematous nasal mucosa that is friable with gold stippling. When asked, he states that his mood is fine. Which of the following is the most likely cause of this patient’s condition?

A healthy 40-year-old man is participating in a study in which he is given an intravenous injection of insulin to induce hypoglycemia. The graph shows serum concentrations of catecholamines at baseline and the peak values at the nadir of serum glucose. Which of the following most likely underlies the different magnitude of the epinephrine and norepinephrine responses?