A 22-year-old primigravid woman at 20 weeks’ gestation comes to the physician because of a 4-day history of dull pelvic pain that radiates to the right side of her labia majora. She says, “It feels like something is pulling.” She is concerned that she is going into labor. Physical examination shows no dilation of the cervix. Stretching of which of the following ligaments is the most likely cause of this patient’s pain?

A 27-year-old man with AIDS comes to the physician because of a 6-week history of progressive memory loss, imbalance, clumsiness, and difficulty finding words. The symptoms began with an inability to concentrate 3 months ago. He is not adherent to combination antiretroviral therapy and recently recovered from Pneumocystis jirovecii (formerly P. carinii) pneumonia. An MRI shows diffuse, poorly defined, bilateral hyperintensities within cerebral white matter. A stereotactic biopsy specimen shown in the photomicrograph depicts cells scattered predominantly along the perivascular spaces. Which of the following is the most likely diagnosis?

Human gene fragments in appropriate vectors may be introduced into bacterial cells by transformation. Which of the following is most likely to be used to transfer cloned human genetic material to bacteria?

An investigator is conducting a study of the effects of a newly discovered spider venom on neuromuscular transmission. An isolated nerve muscle preparation is bathed in a solution containing the venom; there is a decrease in the end-plate potential amplitude following stimulation of the nerve. The presence of the venom does not change the amplitude of the nerve action potential or the muscle potential change in response to the exogenous application of acetylcholine to the neuromuscular junction. Blockade of which of the following by the venom best explains the decreased end-plate potential amplitude in this study?

A 29-year-old woman comes to the physician because of a 6-day history of rash, joint pain, and fatigue. Her temperature is 37.4°C (99.4°F), and blood pressure is 150/90 mm Hg. Physical examination shows a raised, erythematous, blotchy malar rash and mild peripheral edema. There is tenderness and swelling of several joints. Laboratory studies show:

Which of the following serologic studies is most likely to produce a false-positive result in this patient?

A previously healthy 18-year-old man is brought to the emergency department by his mother 45 minutes after she found him crouched in his closet, saying he had to hide from the intruders “from that other place.” There were no intruders in the house. He has no history of alcohol or drug use. He appears afraid of the physician and sits far away from her. During the interview, he says he has heard two male voices in his head for the past 2 weeks. Physical examination and laboratory studies show no abnormalities. Which of the following is the most likely diagnosis?

A 3-month-old girl is brought to the physician 2 days after the mother felt masses in the infant’s groin while bathing her. Physical examination shows bilateral inguinal hernias and a shallow vagina that ends blindly. Serum studies show increased concentrations of luteinizing hormone, follicle-stimulating hormone, testosterone, and dihydrotestosterone. During repair of the hernias, gonads are found. A biopsy specimen of the gonads shows bilateral testes. The karyotype is 46,XY. Ultrasonography shows no uterus or fallopian tubes. Which of the following is the most likely cause of the findings in this patient?

A 35-year-old man comes to the physician because of a 3-year history of an enlarging nose, coarsening of his facial features, muscle weakness, and increased hand and foot size. Physical examination shows a large fleshy nose and prognathism. Fasting serum studies show increased insulin-like growth factor-l, glucose, and triglyceride concentrations. Increased serum growth hormone concentrations do not decrease after the administration of oral glucose. Compared with a healthy patient, which of the following best describes the metabolic changes in this patient?

A 1-day-old female newborn with aniridia undergoes genetic testing. Her father and several other paternal family members also have aniridia. Chromosomal microarray analysis of the patient shows no gain or loss of gene dosage throughout the genome, including the chromosome 11 p15 region that contains the PAX6 commonly mutated in patients with aniridia. Routine chromosomal analysis shows a balanced translocation between chromosomes 1 and 11, with the chromosomal breakpoint on chromosome 11 being 11p15. The same balanced translocation is also found in all of the affected family members but not in the unaffected family members. However, DNA sequencing of the PAX6 located at 11 p15 shows no mutation in any of the exons of PAX6 in the patient. Which of the following is the most likely cause of this patient’s condition?

An investigator is studying Po2 in an experimental animal. It is found that Po2 in the renal vein is relatively high compared with venous Po2 from most other organs. Which of the following best explains this finding?

A study is conducted to assess the accuracy of a new rapid test to detect a virulent bacterial infection. This infection has an 80% mortality rate if it is not identified early in its course; however, prompt administration of antibiotics decreases the mortality rate to less than 5%. The risks of this antibiotic therapy are minimal. A total of 10,000 participants are enrolled and undergo assessment with the new test. The graph shows the distribution of infected and noninfected participants according to the results of the test. Which of the following labeled points is most appropriate for use as the optimal diagnostic cut point for results of this test?

A 28-year-old woman delivers a full-term newborn who has generally flattened facial features, including a broad, flat nose, and bilateral clubfoot deformity with tibial torsion. Ultrasonography at 18 weeks’ gestation showed oligohydramnios and small dysplastic fetal kidneys with scattered cysts. Which of the following general classifications best describes the extrarenal physical features?

A 12-year-old girl is brought to the emergency department 15 minutes after she accidentally sliced her left palm with a knife. Physical examination shows a 2-cm laceration over the left palm. The wound is cleansed and sutured. One week later, the sutures are removed. At this time, which of the following factors is most instrumental in the migration of fibroblasts into the area of wound healing?

A 12-year-old boy is brought to the physician by his parents because of bed-wetting. He urinates 10 to 15 times each day. He says that he is constantly thirsty and drinks large quantities of liquid throughout the day. Urinalysis shows a specific gravity of 1.003. A 24-hour urine collection shows a creatinine clearance of 140 mL/min, with a total urine volume of 7600 mL and urine osmolality of 230 mOsmol/kg H20. A tumor affecting which of the following hypothalamic nuclei is most likely involved in producing this patient’s symptoms?

A 70-year-old man comes to the physician because of a 3-day history of shortness of breath and right-sided chest pain. His respirations are 25/min. Chest x-rays show a right pleural effusion and an associated ipsilateral, scallop-shaped pleural density. Examination during an open lung biopsy shows a thick, firm, white pleural tumor that ensheathes the right lung. Which of the following is the strongest predisposing risk factor for this patient’s condition?

A 23-year-old woman comes to the physician because of a 1-week history of intermittent episodes of fever and chills, followed by a rash. She has had four operations to correct scoliosis, in addition to undergoing a tonsillectomy, an appendectomy, removal of a lipoma from her scalp, and dermabrasion to correct acne scarring. She was admitted to the hospital 1 year ago for 2 weeks because of nausea and vomiting of unexplained origin. Her temperature is 37°C (98.6°F). Physical examination shows approximately 12 evenly spaced punctate marks in a linear pattern on the abdomen and upper and lower extremities. There are no marks on the face or back. Which of the following is the most likely diagnosis?

A 20-year-old man is brought to the physician because of a 4-hour history of abdominal pain, nausea, and vomiting. He says that he had been drinking ethanol heavily all weekend, and he took three doses of acetaminophen within 2 hours after the onset of a severe headache Monday morning. This patient is at increased risk for liver injury because of which of the following actions of ethanol?

The graph shows diastolic and end-systolic relationships of the left ventricle. The solid line shows the control pressure-volume loop in a single cardiac cycle. If a healthy person is given nitroprusside and reflex responses are blocked, which of the following labeled end-systolic pressure points is most likely?

The patient whose cardiac function is illustrated most likely has which of the following?

A 66-year-old man with type 2 diabetes mellitus and hypertension is brought to the emergency department 30 minutes after the sudden onset of left eyelid drooping, double vision, and mild weakness of the right hand and leg. His pulse is 88/min and regular, and blood pressure is 159/99 mm Hg. Examination of the head shows a substantially droopy left eyelid, and in primary gaze, the left eye is exotropic and somewhat lower than the right. He has slowed finger movements on the right, a pronator drift with the right hand, and mild hyperreflexia on the right. Which of the following is the most likely site and diagnosis of the patient’s lesion?

A 13-year-old girl is brought to the physician by her mother because of a mass in her armpit for 3 days. She has a history of several similar masses since early childhood that have resolved with treatment. She also has had several episodes of pneumonia, rhinitis, and perianal abscesses since birth. Her temperature is 37°C (98.6°F). Physical examination shows a 2-cm, raised, red, tender, fluctuant mass in the right axilla. There is mild hepatosplenomegaly. A complete blood count shows a mildly increased leukocyte count. A chest x-ray shows bilateral interstitial infiltrates. A photomicrograph of lung tissue obtained on biopsy is shown. A nitroblue tetrazolium test shows deficient reduction by granulocytes. The axillary mass is incised and drained, and culture of the fluid grows Staphylococcus aureus. Which of the following is the most likely diagnosis?

A 40-year-old man is evaluated because his skin is extremely sensitive to sunlight. Exposure to the sun causes the formation of vesicles and blisters on the skin, which frequently take weeks to heal. He is diagnosed with a disorder caused by the increased synthesis of compounds in the skin that are subject to excitation by visible light. Which of the following biochemical pathways is most likely defective in this patient?

A 50-year-old man is brought to the emergency department because of a 2-hour history of vomiting blood. He is in acute distress. His temperature is 37.5°C (99.5°F), pulse is 110/min, respirations are 18/min, and blood pressure is 80/50 mm Hg. Despite appropriate treatment, he dies shortly thereafter, and an autopsy is done. The gross and microscopic appearances of a section of the esophagus are shown. Which of the following best explains these autopsy findings?

An investigator is studying the adverse effects of a proteasome inhibitor, bortezomib, on immune responses. Bortezomib is administered to a group of patients with relapsed multiple myeloma, and immune responses are observed. Which of the following immunologic processes is primarily affected by this drug?

A 76-year-old woman comes to the emergency department because of a 6-hour history of moderate right low back and flank pain. Vital signs are within normal limits. Physical examination shows mild vertebromediastinal recess (costovertebral angle) tenderness. Urinalysis shows no blood. ACT scan of the pelvis shows hydronephrosis with obstruction of the right ureter caused by external compression at the pelvic brim from a vascular structure. This patient most likely has an aneurysm of which of the following arteries?

Shortly after delivery, a full-term male newborn is found to have black hair with a white forelock. His mother, a brunette, also has a white forelock and wears hearing aids. Physical examination shows heterochromia of irides. Otoacoustic emissions testing and brain stem auditory evoked responses show bilateral sensorineural hearing loss. Which of the following is the most likely cause of the findings in this patient?

A study is done to determine the relationship between use of oral contraceptives and cervical cancer. Study subjects include 50,000 women who are using oral contraceptives and 50,000 women who have had a tubal ligation. After 2 years of follow-up, the rate of in situ cervical cancer is 18 per 10,000 in the oral contraceptive group and 3 per 10,000 (p < 0.05) in the tubal ligation group. Which of the following is the estimated relative risk of cervical cancer among women who have had a tubal ligation compared with women who use oral contraceptives?

A 45-year-old woman is brought to the emergency department 30 minutes after the sudden onset of left-sided facial drooping and left arm and leg weakness. One week ago, she returned from a business trip that involved a 6-hour airplane flight. She has no history of major medical illness. She does not smoke. Her only medications are an oral contraceptive and occasional acetaminophen for headache. Her pulse is 88/min and regular, and blood pressure is 160/90 mm Hg. Physical examination shows left-sided facial paralysis. Examination of the left lower extremity shows swelling, tenderness, and localized erythema over the calf. Muscle strength is 3/5 in the left upper and lower extremities. Cardiac examination shows no abnormalities. Echocardiography is most likely to show which of the following findings in this patient?

A 34-year-old woman comes to the physician because of a 10-year history of constipation. She usually has fewer than three bowel movements weekly. She often has bloating and cramping, and she has to strain and apply perineal pressure to defecate. She says that she does not have problems with sleep, appetite, or energy. Palpation of the abdomen produces diffuse discomfort; bowel sounds are present. Which of the following is the most likely cause of this patient’s gastrointestinal symptoms?

During an experiment, a solution of mixed fatty acids is injected into the duodenum of an experimental animal. Under these conditions, the clearance rate of an intravenous glucose load from the circulation is doubled. In contrast, an injection of an equal volume amount of 0.9% saline into the duodenum has much less effect on the plasma clearance rate of glucose. These findings are most likely caused by the secretion of which of the following hormones?

An 18-month-old boy has pinched, wrinkled facies and total loss of subcutaneous fat. He is alert. His height is at the 50th percentile and his weight is at the 2nd percentile for his age. The liver is not enlarged, and there is no edema. Which of the following is the most likely diagnosis?

A 26-year-old man comes to the physician because of fever, cough, chest pain, and malaise for 2 weeks. He moved to central California 6 months ago. A complete blood count shows mild eosinophilia. A chest x-ray shows patchy bronchopneumonia. Culture of the sputum grows a mold with the morphology shown in the photomicrograph, with the arrow indicating the infectious particle. Which of the following is the most likely causal organism?

A 67-year-old white woman undergoes punch biopsy of an urticarial lesion on her back. When the biopsy specimen container is received in the laboratory, it is determined that it contains two specimens instead of one. Review of the additional specimens received from the physician’s office indicates that specimens from two separate patients were inadvertently shipped in the same container. The other specimen is from the back of a dark-skinned, 58-year-old Nigerian woman. An increase in which of the following in the specimen from the Nigerian patient is most likely to differentiate these two specimens?

A 4-year-old boy has had a viral upper respiratory tract infection for the past 3 days. Clearance of the virus is most dependent on which of the following?

A 33-year-old woman comes to the physician because of a 3-day history of nausea and light-headedness. Her last menstrual period was 5 weeks ago. She is apprehensive. Physical examination shows no abnormalities. Her serum β-human chorionic gonadotropin concentration is increased. At this stage in the pregnancy, progesterone is most likely produced within which of the following structures?

A 70-year-old man with metastatic prostate cancer has been taking leuprolide for the past 3 months. Which of the following best describes this patient’s current serum luteinizing hormone (LH) and testosterone concentrations compared with concentrations before treatment?

A 57-year-old man dies 5 days after a stroke. He had progressively severe hypertension over the past 2 years but refused treatment. Blood pressure just prior to the stroke was 220/110 mm Hg. Which of the following is the most likely histologic finding in his kidneys at autopsy?

A 14-year-old boy is brought to the physician by his parents because of increasingly severe left knee pain during the past week. The pain is exacerbated by running or kneeling. He plays multiple sports and is currently in the middle of soccer season. There has been no recent trauma to the area or related sports injuries. Physical examination shows full range of motion of both lower extremities. There is a discrete area of swelling just below the left patella over the proximal portion of the tibia. Palpation of the area produces pain. Pain is also reproduced when he does a full squat. Examination of the right knee shows no abnormalities. Which of the following is the most likely cause of this patient’s condition?

A study is conducted in which the right renal artery of an experimental animal is constricted to decrease arcuate artery pressure by 20 mm Hg. Measurement of inulin clearance shows that renal artery constriction has no effect on glomerular filtration rate (GFR). Which of the following best explains the maintenance of a constant GFR in this experiment?

An 83-year-old woman is brought to the physician by her daughter to discuss the results of a complete dementia work-up. The patient has had mild memory impairment for 8 months. She takes no medications. Vital signs are normal. Her Mini-Mental State Examination score is 23/30. A rapid plasma reagin is 1:4, and a microhemagglutination assay for Treponema pallidum is positive. Which of the following is the best next step for the physician?

The local health department is investigating an outbreak of acute hepatitis A in two city districts by reviewing the medical records at a health center in each district. The investigators plan to analyze the clinical and epidemiologic characteristics of patients who tested positive for hepatitis A serum IgM antibody compared with characteristics of those who tested negative for the antibody. Which of the following best describes this study design?

A 53-year-old man comes to the physician because of a 6-day history of shortness of breath, cough, and pleuritic chest pain. His temperature is 38.9°C (102°F), and respirations are 35/min. Sputum is purulent and rust colored. Physical examination shows decreased breath sounds, and crackles are heard at the left base. A Gram stain of sputum shows gram-positive diplococci. A chest x-ray shows left-sided lobar consolidation. Which of the following anatomic structures most likely allowed rapid spread of organisms between alveoli to involve the entire left lobe in this patient?

A female newborn is born at 39 weeks’ gestation following an uneventful pregnancy. The Apgar scores are 10 at 1 and 5 minutes, respectively. The newborn is at the 50th percentile for length and 25th percentile for weight. She has normal morphologic features. The parents are told she has an enzyme defect that, if left untreated, will result in failure to attain early developmental milestones, microcephaly, hyperactivity, seizures, intellectual disability, and a mousy odor of the skin and urine. The patient’s diet needs to contain which of the following to provide substrate for catecholamine production?

A 28-year-old woman has had fatigue and heavy menstrual periods during the past year. She is a vegetarian who eats eggs and dairy products. Her diet contains little fruit. Which of the following erythrocyte types is most likely to be present on a peripheral blood smear from this patient?

The graph shows the mean steady state plasma concentration of Drug X as a function of time in a subject who has normal weight (solid curve) and a subject who is obese (dashed curve). Both subjects take 10 mg of Drug X daily. Which of the following best describes the disposition of Drug X in the obese patient compared with the patient who has normal weight?

A 4-year-old girl has acute lymphoblastic leukemia that has not responded to aggressive treatment. The physician recommends palliative care to the parents and suggests that they talk to their daughter about her impending death and answer any questions that she may have. The parents ask the physician to help them respond to her questions. When speaking with the child, the parents should anticipate that she will most likely understand death as which of the following?

A 38-year-old woman with asthma comes to the physician for advice concerning contraception. She is sexually active with one partner, and they use condoms inconsistently. Current medications include inhalational fluticasone and albuterol. She has smoked one-half pack of cigarettes daily for 20 years and drinks two alcoholic beverages daily. She does not use illicit drugs. Her maternal grandmother developed breast cancer at the age of 58 years. She is 157 cm (5 ft 2 in) tall and weighs 82 kg (180 lb); BMI is 33 kg/m2. Her vital signs are within normal limits. Physical examination shows no other abnormalities. This patient should be advised to avoid the use of an oral contraceptive because of which of the following historical factors?

A 56-year-old woman comes to the physician because of a 3-week history of increasing weakness of her arms and legs. She has smoked 1 pack of cigarettes daily for 30 years. Physical examination shows pronounced weakness of the hip girdle muscles and lesser weakness of the shoulder girdle muscles, both of which improve with repetitive testing. A chest x-ray shows a hilar lung mass. Electromyography is compatible with a malfunction of the neuromuscular junction. Impairment of which of the following is the most likely cause of these findings?

A transgenic animal containing a targeted mutation in the gene coding for macrophage colony-stimulating factor is prepared. Which of the following generalized skeletal abnormalities is expected in this animal?

A 65-year-old woman dies 6 months after the onset of severe headaches. Her brain as seen at autopsy is shown in the photograph. Which of the following is the most likely cell of origin of this neoplasm?