A male newborn is found to have an increased serum phenylalanine concentration on routine screening. The increased serum phenylalanine concentration is best explained by a defect in which of the following processes?

A healthy 22-year-old man participates in a study that analyzes the effects of various therapies on gastrointestinal motility. A manometric tracing of this man is shown. This manometric pattern is most likely due to binding of which of the following neurotransmitters with its respective receptor in the stomach?

An 18-year-old man is brought to the emergency department 30 minutes after a motorcycle collision. He has lost a significant amount of blood. His pulse is 120/min, and blood pressure is 90/70 mm Hg. Physical examination shows a severe laceration of the left calf. Rapid infusion of 0.9% saline is started to restore his vascular volume deficit. The solid curves in the graph show the relationship between right atrial pressure and cardiac output (cardiac function curve). The dashed lines show the relationship between cardiac output and right atrial pressure (vascular function curve). Point X is the preinfusion equilibrium point. Which of the following is the most likely new cardiac and vascular equilibrium point following the infusion?

A 10-year-old boy is brought to the emergency department 30 minutes after sustaining injuries in a skateboard accident. His vital signs are within normal limits. Physical examination shows tenderness to palpation over the right wrist. An x-ray shows a fracture of the right radius and ulna. He is treated with cast immobilization extending over the right elbow. He is no longer able to move his forearm muscles. Which of the following is most likely to occur in the immobilized muscles after 3 weeks in the cast?

A full-term male newborn has severe hypotonia. His 20-year-old mother shows little facial expression. When she shakes the physician’s hand, she has difficulty releasing her grip. Which of the following genetic phenomena is the most likely cause of these findings?

A 28-year-old woman and her 40-year-old husband both have albinism; none of their three children is affected. A pedigree is shown. Which of the following genetic mechanisms best explains the absence of albinism in their children?

A 32-year-old man sustains a head injury in a motorcycle accident and is admitted to the intensive care unit. Six days later he becomes confused and is very thirsty. His serum sodium concentration is 158 mEq/L, and his urine output is 6.1 L/day. These findings most likely indicate that he has a disorder that is affecting which of the following labeled parts of the nephron shown?

A 13-year-old boy is brought to the physician because of a 4-week history of mild left thigh and knee pain that was exacerbated when he jumped off the school bus steps onto the sidewalk this morning. The pain increases with activity. He has no history of serious illness or trauma and takes no medications. He is at the 50th percentile for height, 90th percentile for weight, and 97th percentile for BMI. His temperature is 37°C (98.6°F), pulse is 80/min, respirations are 16/min, and blood pressure is 115/65 mm Hg. Genital development is Tanner stage 3. Physical examination of the left lower extremity shows no muscle tenderness. Muscle tone and strength are normal in both lower extremities. Range of motion of the left knee is full and elicits no pain. Internal rotation of the left hip is limited by pain. Which of the following is the most likely diagnosis?

A 79-year-old woman is brought to the emergency department because of pain in her left hip that began after she fell in her home. Physical examination shows a shortened and externally rotated left lower extremity. An x-ray shows an intertrochanteric fracture of the femur. Which of the following muscles best contributes to the lateral rotation of the thigh?

A previously healthy 12-year-old girl is brought to the physician because of a 1 -week history of brief generalized tonic-clonic seizures. Her family recently emigrated from Mexico. Physical examination shows no abnormalities. A CT scan of the head shows multiple calcified nodules and some cysts. The most likely cause of her seizures is infection with which of the following causal organisms?

During a clinical study, an investigator examines the effects of monoamine oxidase inhibitors to treat certain types of major depressive and phobic anxiety disorders. The concentration of which of the following compounds is most likely to be increased as a result of this treatment?

A 24-year-old man comes to the emergency department because of a 2-hour history of severe abdominal pain. His pulse is 110/min. Abdominal examination shows distention. An x-ray of the abdomen while the patient is sitting upright and an image from upper gastrointestinal series are shown. Based on the findings shown, this patient most likely has which of the following developmental anomalies?

A 32-year-old man comes to the physician for a health maintenance examination. His maternal uncles and grandfather had hypertension, renal calculi, enlargement of both kidneys, and decreased renal function. His maternal grandfather died of a ruptured intracranial berry aneurysm. Physical examination shows no abnormalities. Ultrasonography shows five to seven cysts in both kidneys. This patient most likely has a mutation in the gene that encodes which of the following proteins?

During a clinical study, nine patients are given a new antihypertensive drug. One week later, their serum creatinine concentrations are measured, and the results are shown:

If one of the 0.9 values were now mistakenly entered as 1.2, which of the following would the most likely effect be on the mean, median, and mode?

A 54-year-old woman comes to the physician because of a 5-day history of severe mid-back pain. Physical examination shows point tenderness over the T6 vertebra. Serum studies show a calcium concentration of 13.4 mg/dL; urinalysis shows Bence Jones proteins. Which of the following is the most likely cause of this patient’s hypercalcemia?

During an investigational study, antibodies are induced that bind to and inactivate inhibin in female experimental animals. On examination of these animals, which of the following is the direct result of the inactivation of inhibin?

A 26-year-old woman is diagnosed with a metastatic anaplastic tumor. Immunohistochemical studies of a biopsy specimen show large quantities of desmin in the tumor cells. Based on these findings, these cells most likely originated in which of the following tissues?

An 82-year-old woman comes to the physician because of constant severe lower abdominal pain and fever for 24 hours. Laparoscopic examination shows severe diverticulosis and perforated diverticulitis. In spite of appropriate therapy, she dies 2 days later. Her liver at autopsy is shown. Which of the following is the primary component of the material shown on the hepatic surface?

A 55-year-old man is admitted to the hospital because of a 2-day history of vomiting and severe abdominal pain in the right upper quadrant. He drinks six 12-ounce beers daily. Abdominal examination shows spider angiomata. The liver is hard and nodular on palpation. A CT scan of the abdomen is shown; the arrow indicates a mass. Hypertension of which of the following veins is most likely in this patient?

A 69-year-old man is admitted to the hospital after having a myocardial infarction. He cannot take aspirin because of a history of bronchospasm. At discharge, a substitute drug that inhibits platelet function is prescribed. This drug most likely has which of the following mechanisms of action?

An investigator is studying the efficacy of distinct vaccine formulations directed against the capsular polysaccharides of Neisseria meningitidis. The carbohydrates are chemically conjugated to various compounds and injected into laboratory mice. Titers of anticapsular IgG antibodies are then measured. Which of the following compounds is most likely to induce increased titers of these antibodies when conjugated to the polysaccharides?

A 20-year-old woman comes to the physician because of a 10-day history of a vaginal discharge and vaginal itching and soreness. Current medications include a multivitamin and an antibiotic for acne. Pelvic examination shows vulvar erythema and edema and a thick, white vaginal discharge. Her vaginal fluid pH is 4.2. A photomicrograph of the vaginal discharge is shown. The most appropriate pharmacotherapy for this patient is an oral agent with which of the following mechanisms of action?

A 68-year-old woman with hypertension comes to the physician because of concerns about recent home blood pressure measurements. She says that her systolic blood pressures have ranged from 140 mm Hg to 160 mm Hg during the past 10 days. She has generalized anxiety disorder and major depressive disorder. Medications include amlodipine, citalopram, and hydrochlorothiazide. She appears anxious. Her blood pressure is 145/94 mm Hg. Physical examination shows no other abnormalities. While discussing treatment options, the patient says, “You are not taking good care of me; you must not like me very much.” Which of the following is the most appropriate initial response by the physician?

A newborn is evaluated for microcephaly, cataracts, and chorioretinitis. The mother developed an illness in the first trimester of pregnancy characterized by low-grade fever, a faint erythematous rash, occipital lymphadenopathy, and joint stiffness. The illness resolved within 1 week without complications. She did not receive any immunizations prior to the pregnancy. Which of the following viruses is the most likely cause of the newborn’s illness?

A 55-year-old woman comes to the physician because of a 2-day history of fever and the recent onset of cough productive of blood-tinged sputum. She also has had progressive shortness of breath during physical activity. She has smoked 2 packs of cigarettes daily for 41 years. Her temperature is 38.6°C (101.5°F), pulse is 95/min, respirations are 22/min, and blood pressure is 135/84 mm Hg. Breath sounds are decreased, and crackles are heard in the right middle lung field. A chest x-ray shows consolidation of the right middle lobe and a possible mass in the right hilar region. ACT scan of the lungs shows a 4-cm mass involving and obstructing the proximal right middle lobe bronchus. Which of the following is the most likely type of lung neoplasm?

In a series of 1000 patients with colonic polyposis, three developed colonic malignancies over a 2-year follow-up period. In 1000 control patients without colonic polyposis, one developed a colonic malignancy over the 2-year follow-up period. Which of the following factors most limits the ability to conclude that polyposis is associated with an increased risk for subsequent malignancies?

A 76-year-old man with a 5-year history of progressive dementia, Alzheimer type, is brought to the emergency department by his son, who found him weak and unable to get out of bed. The patient has had increasing problems caring for himself while living alone and has lost 11 kg (25 lb) over the past year. He takes no medications. He is 173 cm (5 ft 8 in) tall and weighs 42 kg (92 lb); BMI is 14 kg/m2. He is alert and talkative. Vital signs are normal. Physical examination shows sparse brittle hair and a red smooth tongue. There is general atrophy of interosseous and temporalis muscles, loss of subcutaneous fat, and edema of the lower extremities. He is oriented to person but not to place or time. Laboratory studies show:

Liver function tests show no abnormalities. An x-ray of the chest shows a healed granuloma in the right upper lobe of the lung. Which of the following is the most likely explanation for this patient’s condition?

A 50-year-old man with septic shock develops diffuse cortical necrosis in the kidneys. He dies 2 weeks later. At autopsy, gross examination of the cortex of the kidneys shows changes indicative of acute ischemic infarction. Histologic examination of the kidney medulla shows no abnormalities. Based on these findings, which of the following structures is most likely to show pathologic changes?

An 18-year-old man develops a painless 1×1-cm ulcer on his penis, followed 4 weeks later by an erythematous maculopapular rash involving the palms and soles. The drug of choice for treatment of this disease inhibits which of the following microbial processes?

A 3-month-old girl is brought to the physician by her father because of developmental delay and delayed growth. She is below the 3rd percentile for length and weight. Physical examination shows coarse facial features, generalized hypotonia, bilateral hip dislocation, and inguinal hernias. Laboratory studies show an increased serum activity of lysosomal enzymes. Urine studies show no mucopolysaccharides. This patient most likely has a defect in which of the following biochemical pathways?

A 12-year-old boy with severe deafness is brought to the physician because of a 3-month history of episodes of loss of consciousness. Physical examination shows no abnormalities except for severe bilateral sensorineural hearing loss. An ECG shows a long QT interval. This patient most likely has a mutation in the gene that encodes which of the following proteins?

A previously healthy 72-year-old man is brought to the physician because of weakness and fatigue. His hemoglobin concentration is 9.2 g/dL, leukocyte count is 5400/mm3, and platelet count is 350,000/mm3. A peripheral blood smear is shown. Which of the following is the most likely cause of these findings?

A 28-year-old African American man comes to the physician because of a 3-month history of mild fatigue and weakness; he has had a 4.5-kg (10-lb) weight loss during this period. He also has a 6-month history of dry cough associated with chest pain and shortness of breath. The patient is married with two children, ages 2 and 3 years. He says that no one else at home has similar symptoms. He is a carpenter. He has several pets, including a dog, two cats, and a bird. He spent a week in Mexico approximately 1 year ago. He has smoked one-half pack of cigarettes daily for 10 years. He is 178 cm (5 ft 10 in) tall and weighs 70 kg (154 lb); BMI is 22 kg/m2. Mild wheezes are heard. Physical examination shows no other abnormalities. A chest x-ray shows bilateral hilar adenopathy and right paratracheal node enlargement. Biopsy specimens obtained via fiberoptic bronchoscopy show noncaseating granulomas. Test results of the biopsy specimen for acid-fast bacilli and fungi are negative. Which of the following is the strongest predisposing risk factor for this patient’s condition?

A 73-year-old woman is admitted to the hospital 2 days after she fell while walking down her front steps. She has severe back pain. She has a 7-year history of polymyalgia rheumatica and a 20-year history of hypertension. Current medications include lisinopril, prednisone, vitamin D, and a multivitamin. She appears frail. Physical examination shows thoracic kyphosis and multiple ecchymoses over the dorsa of the hands. There is a tender point on percussion of the mid spine. A spinal x-ray shows multiple vertebral compression fractures. If a bone biopsy specimen were obtained from this patient, it would most likely show which of the following findings?

A healthy 30-year-old woman is traveling on a commercial airliner where the cabin’s barometric pressure is measured at 565 mm Hg. The inspiratory partial pressure of alveolar oxygen in this woman is most likely which of the following (in mm Hg)?

A 7-year-old boy is brought to the physician by his parents because of a 1-month history of progressive double vision and a 2-week history of imbalance. Physical examination shows weakness of abduction of the right eye, mild weakness of the left extremities, increased muscle stretch reflexes of the left extremities, and gait ataxia. Which of the following is the most likely diagnosis?

A 28-year-old woman comes to the physician for a health maintenance examination. During the interview, she tearfully tells the physician that she and her new husband are having problems. She says she wants to go out with friends, but he does not enjoy being with people, preferring individual activities such as hiking. She says he seems indifferent to sexual intimacy and neither shows much emotion nor understands her feelings at all. Which of the following personality styles best explains the husband’s behavior?

A 25-year-old man is lost in the desert for 1 week with an ample supply of water but no food. Which of the following changes in enzyme activities and regulatory molecule concentrations in liver is most likely in this patient?

A 52-year-old woman has a 10-year history of recurrent urinary tract infections. Urinalysis shows:

Microscopic analysis of urine sediment shows numerous erythrocytes, leukocytes, and crystals. Her symptoms do not respond to therapy, and she undergoes a left nephrectomy. A photograph of the resected specimen is shown. Which of the following is the most likely causal agent?

An investigator conducts a study of cranial nerve regeneration among two groups of experimental animals. During the study, the facial nerves are severed in one group (Group X) and the optic nerves are severed in the second group (Group Y). Three months later, it is found that the severed facial nerves among animals in Group X have regenerated, but the severed optic nerves among animals in Group Y have not regenerated. Which of the following best explains the absence of nerve regeneration among the animals in Group Y?

A 70-year-old woman comes to the physician because of a 3-month history of frequent constipation and fatigue. She has had a 4.5-kg (10-lb) weight loss during this period. Her vital signs are within normal limits. Abdominal examination shows mild tenderness. Rectal examination shows a 10-cm firm mass. Laboratory studies show:

This patient is at greatest risk for complications involving which of the following organs?

A 24-year-old man comes to the physician because of nasal congestion, a watery nasal discharge, and sneezing. He says that these symptoms happen each spring, when grass and tree pollens are abundant. Which of the following types of drugs is most likely to be effective in relieving these symptoms in the short term?

 A 22-year-old woman is found to be HIV positive after sexual contact with a partner with HIV infection. Combination therapy with lamivudine (3TC), ritonavir/lopinavir, and zidovudine (AZT) is initiated. Three months later, genomic typing shows that her HIV strain has become resistant to ritonavir/lopinavir. The cause of this resistance is most likely the acquisition of a mutation in a gene that is critical for which of the following viral processes?

A 28-year-old woman comes to the physician because of heavy menstrual bleeding since menarche at the age of 13 years. She also has a lifelong history of easy bleeding with minor cuts. She says several family members of both genders have prolonged bleeding with minor surgical procedures. Physical examination shows no abnormalities. Laboratory studies show a deficiency of von Willebrand factor. Which of the following mechanisms is the most likely cause of this patient’s bleeding disorder?

A 3-year-old girl is found to have a grade 4/6, loud, harsh, high-pitched holosystolic murmur that radiates over the precordium and a palpable thrill at the left sternal border. Which of the following defects is most likely in this patient?

A 28-year-old man comes to the physician because of a 2-day history of an abscess at the site of a splinter on his right index finger. The leukocytes in this abscess initially localized to the site of inflammation because of an endothelial adhesion molecule that binds ligands on the surface of the leukocyte. Which of the following molecules is the most likely cause of the adhesion to the endothelial surface at the site of inflammation?

The table summarizes the result of a study of the relationship between smoking and death from lung cancer:

Which of the following best describes the attributable (excess) risk per 1000 persons from heavy smoking in those with lung cancer?

A 78-year-old man comes to the physician because of a 1-week history of blisters over several areas of his body. A photograph of the lesions is shown. Direct immunofluorescence of the affected areas shows linear deposition of IgG and C3b at the dermal-epidermal junction. Which of the following best describes the function of the target structure to which IgG is binding in this patient?

Which of the following hormones decreases synthesis of prostaglandins and leukotrienes?

An 8-year-old boy is brought to the physician by his parents for a well-child examination. His sister died of leukemia 4 months ago. The parents state that he is sad at times, but he has had only minor performance difficulty at school since his sister died. During the interview, the patient talks about his sister’s death and cries. He then says that he has a headache. Physical examination shows no abnormalities. Which of the following best describes this patient’s condition?