A 43-year-old man comes to the clinic due to poor appetite and abdominal swelling.  The patient has a history of intravenous drug use.  Physical examination is significant for an enlarged liver.  Laboratory results are as follows:

HIV test result is negative.  Liver biopsy shows spherical nodules within the confines of fibrous septa.  The nodules are composed of which of the following proliferating cells?

A 65-year-old woman comes to the office due to clumsiness.  The patient has difficulty with everyday activities such as buttoning her shirt, opening jars, and rising from a chair.  Her muscles feel stiff, and it takes longer for her to walk around her apartment complex.  She also feels sleepy and fatigued during the day.  Her symptoms cause her significant anxiety because the patient lives alone and cares for herself.  Vital signs are normal.  Physical examination shows increased resistance to passive motion in all directions in both the elbows and the wrists.  There is a slight tremor mainly involving the right hand; it is suppressed with purposeful movements.  Muscle bulk, strength, sensation, and reflexes are normal.  Histologic examination of this patient’s brain is most likely to show accumulation of which of the following substances?

A 29-year-old nulligravid woman comes to the office for evaluation of infertility.  The patient has had unprotected intercourse with her partner for the past 18 months without conception.  Her menstrual periods occur every 27-29 days, last 4-5 days, and she has breast tenderness 2 days prior to her menses.  The patient previously used combined oral contraceptives but stopped 2 years ago.  She lost 6.8 kg (15 lb) over the past year with a healthy diet and daily exercise.  The patient’s BMI is 22 kg/m², and her physical examination is normal.  Hysterosalpingogram shows a smooth uterine cavity with partial filling of the fallopian tubes through the isthmus bilaterally, but no intraperitoneal spill of contrast.  Which of the following is the most likely underlying cause of this couple’s infertility?

A 41-year-old man comes to the emergency department due to 2 days of fever and productive cough.  Temperature is 38.6 C (101.5 F).  Physical examination demonstrates crackles in the right upper lung field.  Chest x-ray shows a right upper lobe pneumonia.  Sputum cultures grow Streptococcus pneumoniae.  The bacteria appear to have a mutation in the erm(B) gene that codes for insertion of a methyl group into a pocket of the 23S rRNA of the 50S ribosomal subunit.  Resistance to which of the following antibiotics would be expected in this patient as a result of this genetic modification?

A 1-hour-old girl is evaluated in the nursery.  The patient was born via spontaneous vaginal delivery to a 30-year-old primigravida at 38 weeks gestation.  The mother had no prenatal care.  Vital signs are normal.  The anterior fontanelle is open, soft, and flat.  The oropharynx is clear.  The neck is supple, and there is a large, doughy mass covered by skin above the left clavicle and lateral to the sternocleidomastoid muscle.  The mass transilluminates when a light source is applied to the neck.  The lungs are clear bilaterally, and cardiac examination is unremarkable.  The abdomen is soft without organomegaly.  This patient’s clinical findings are most likely caused by which of the following genetic abnormalities?

Researchers are investigating the effects of various electrolytes on the membrane potential of isolated neurons.  During one of their experiments, an action potential recorded from a neuron under normal physiologic conditions reaches a peak value of +40 mV.  The researchers then change the concentration of one of the electrolytes and then record another action potential.  The second action potential only reaches a peak value of +10 mV.  Which of the following changes would best explain the observed findings?

A 24-year-old man comes to the office to discuss a rash.  He has a 5-day history of a red outbreak on his hands, forearms, and legs.  The patient is a graduate student in biology and had returned from an overnight field study just prior to the onset of symptoms.  He otherwise feels well, although the week before the trip he had taken penicillin for streptococcal pharyngitis.  Past medical history is unremarkable.  Temperature is 36.9 C (98.4 F), blood pressure is 118/72 mm Hg, and pulse is 60/min.  On examination, there are raised, erythematous spots and streaks in the affected areas.  Which of the following is the most likely cause of this patient’s symptoms?

A 5-year-old girl with sickle cell disease is brought to the emergency department by her parents due to fatigue.  The patient has had a cough and runny nose for the past 3 days.  She has not wanted to eat, and today, she could not get out of bed due to feeling weak.  In addition to daily penicillin and folic acid, the patient began taking hydroxyurea 2 weeks ago.  Temperature is 37.9 C (100.2 F), pulse is 180/min, and respirations are 30/min.  Pulse oximetry is 98% on room air.  The patient is pale and appears tired.  There is faint scleral icterus.  Cardiopulmonary examination is unremarkable.  The abdomen is tender to palpation and bowel sounds are present.  Peripheral pulses are weak.  The results of a complete blood count are as follows:

Which of the following is the most likely underlying cause of this patient’s current presentation?

A 33-year-old woman comes to the office due to intermittent abdominal pain and bloating for approximately 3 months.  The patient also has occasional bulky, frothy stools but has had no blood in her stool or weight loss.  The symptoms occur only when she consumes certain dairy products, such as milk and ice cream, but she can consume yogurt and hard cheeses without symptoms.  Prior to the onset of symptoms, she could eat all dairy products without discomfort.  Her mother, sister, and aunt do not consume dairy products due to similar symptoms.  This patient’s symptoms are most likely related to a change in which of the following?

A 51-year-old man comes to the office for a preventive care visit.  He currently feels well and has no symptoms.  The patient was diagnosed with hypertension 5 years ago, which has been well controlled with losartan.  Thirty years ago, he had mediastinal Hodgkin lymphoma that was treated with external beam radiation therapy, and he has had no relapses.  The patient is up to date with recommended vaccinations and had a normal colonoscopy a year ago.  He does not use tobacco, alcohol, or illicit drugs and takes no other medications.  The patient is a financial advisor, eats a balanced diet, and exercises daily.  Blood pressure is 118/72 mm Hg and pulse is 68/min.  BMI is 24.5 kg/m².  Physical examination shows no abnormalities.  Compared to the general population, this patient is at highest risk of developing which of the following malignancies?

A 34-year-old man comes to the clinic accompanied by his wife.  A few weeks ago, he was discharged from the hospital after being treated for meningoencephalitis.  He has no other significant medical history.  The patient is sitting quietly in the corner and has a flat affect.  He tells the physician that everything is fine.  His wife says, “My husband is not fine.  Since he came home from the hospital, he can’t remember anything I tell him.  He eats constantly, and I find him in the kitchen looking for food in the middle of the night.  He has been acting out sexually, even in public, which is very embarrassing.  At first I thought he was just happy to be out of the hospital, but his behavior isn’t normal.  He was never like this before.”  Damage to which of the following areas in the brain is most likely responsible for this patient’s symptoms?

A 45-year-old woman comes to the office due to 2 days of moderately severe low back pain.  Her pain is located in the lower right back with radiation to the buttock and started after she lifted a heavy bag of potting soil.  There is no associated urinary or bowel incontinence, urinary retention, lower extremity weakness, numbness, or tingling.  Medical history is unremarkable with no prior back problems.  Physical examination reveals paravertebral muscle tenderness.  Bilateral lower extremity power, sensation, and reflexes are normal, and straight-leg raising test is negative in both legs.  Which of the following is the best next step in management of this patient?

A 34-year-old male is recovering from head trauma sustained in a motor vehicle accident.  He is currently in the intensive care unit on mechanical ventilation.  His most recent arterial blood gas analysis shows:

Which of the following additional findings do you most expect in this patient?

A 33-year-old woman is being evaluated for simultaneous kidney and pancreas transplantation.  At age 10, she was diagnosed with type 1 diabetes mellitus, which was complicated by development of diabetic retinopathy and nephropathy.  For the past several years, she has been receiving hemodialysis treatments for end-stage renal disease.  The organ allografts, obtained from a single deceased donor, are transplanted without any periprocedural complications.  The patient is prescribed tacrolimus as part of her posttransplantation immunosuppressive therapy.  This medication is most likely to improve graft acceptance through which of the following mechanisms?

A 34-year-old man comes to the office due to nasal stuffiness and intermittent dizziness for the past several years.  He has no hearing loss or tinnitus.  The patient has used several oral antihistamines and glucocorticoid nasal sprays, but the symptoms persist.  He was also evaluated for infertility and found to have retrograde ejaculation.  Medical history is notable for failure to thrive in childhood, but the patient’s subsequent development was normal.  Physical examination shows boggy nasal mucosa.  Further evaluation reveals a congenital deficiency of dopamine beta-hydroxylase.  This patient is most likely to develop which of the following conditions?

A 35-year-old woman comes to the emergency department after a syncopal episode.  She has persistent chest pressure, dyspnea, and lightheadedness.  The patient has no prior medical issues, and her only regular medication is an oral contraceptive.  She smokes a pack of cigarettes a day and drinks alcohol occasionally.  Physical examination shows altered mental status, cold and clammy skin, and a swollen right lower extremity.  Lungs are clear to auscultation.  CT pulmonary angiogram shows a massive saddle pulmonary embolism occluding the majority of both pulmonary arteries.  Which of the following sets of hemodynamic changes will most likely be observed in this patient?

A 59-year-old man comes to the office for evaluation of progressive exertional dyspnea and poor exercise tolerance over the past several months.  He is unable to extinguish a lit matchstick with a single breath.  The patient has no other medical conditions and takes no medications.  He has smoked tobacco for 40 years.  Blood pressure is 110/68 mm Hg, pulse is 88/min, and pulse oximetry on room air shows an oxygen saturation of 90%.  Breath sounds are reduced, and mild wheezing is heard on chest auscultation.  Lung volume measurements are performed.  Which of the following is the first to increase in this patient’s disease process compared to a normal individual?

Two breast tissue samples are cultured in two separate Petri dishes containing the same medium.  After a certain period of time, cells from the first sample cover the surface of the first dish.  Cells from the second sample also cover the surface of the second dish and are piled up into mounds.  Which of the following statements is most likely true about the cells from the second sample?

A 2-month-old boy is brought to the office for a routine visit.  He was born in Senegal and recently immigrated to the United States with his parents.  The parents report that the child has no problems and he appears to be developing normally.  Vaccine records indicate that the infant received several immunizations prior to relocation, including the oral polio vaccine at birth.  During the office visit, inactivated polio vaccine is administered to the patient.  Which of the following is the most significant advantage of the current vaccine over the vaccine that the patient previously received?

A 63-year-old man comes to the emergency department due to right shoulder pain for the past several weeks.  He also has had headaches, occasional lightheadedness, and tinnitus.  The patient’s wife says that he becomes short of breath with even minimal exertion.  He has a history of hypertension that is well controlled with medications.  The patient has smoked a pack of cigarettes daily for more than 40 years.  Temperature is 37 C (98.6 F).  Physical examination reveals a puffy face and engorged neck veins.  Which of the following labeled structures in the image below is most likely to be affected in this patient?

A 17-year-old boy is brought to the emergency department due to left upper extremity pain and weakness.  Earlier that day he was inadvertently struck in the left arm with a baseball bat when his blindfolded friend was attempting to strike a Piñata.  X-ray of the left arm shows a fracture of the mid-shaft humerus in the region of the spiral groove.  Injury to the nerve traveling in this location is most likely to result in weakness with which of the following actions?

A 24-year-old woman comes to the office after her younger brother was diagnosed with hemophilia.  The patient says that she also has a bleeding tendency and wants to know if she has the disorder.  She reports menorrhagia and a history of prolonged bleeding after tooth extraction.  Both her parents are healthy, but her maternal uncle died of a brain hemorrhage.  Physical examination is unremarkable.  Laboratory evaluation shows factor VIII level is 20% of normal.  Which of the following is the most likely explanation for this patient’s bleeding tendency?

A 22-year-old man comes to the office due to 2 days of fever, cough, and runny nose.  He is a military recruit and is currently undergoing intensive training at a military boot camp in Arizona.  Temperature is 38.6 C (101.5 F).  Examination shows nasal congestion.  Pulmonary examination is unremarkable.  A nasopharyngeal swab specimen is obtained.  Laboratory results are as follows:

Which of the following enzymes is most directly responsible for the replication of the viral genome in the host cells?

A 37-year-old man is hospitalized due to low-grade fever, headache, malaise, and myalgias.  The patient also has difficulty swallowing and painful pharyngeal spasms.  Examination shows muscle spasticity.  His condition progressively worsens to a comatose state, and the patient dies several days later.  Autopsy is performed and brain histopathology reveals a diffuse mononuclear infiltrate and eosinophilic, round, cytoplasmic inclusions in the neurons.  Which of the following is most likely inciting event of this patient’s disease?

Physiologists investigating renal autoregulatory mechanisms conduct a series of experiments in an animal species that closely mimics human physiology.  During one of the experiments, a researcher applies a clip to reduce the diameter of the left renal artery by 75%.  One week later, measurements of multiple renal function parameters are obtained and compared to their preoperative values.  Mean blood pressure within the left renal artery proximal to the clip remains unchanged.  Which of the following physiologic changes is most likely to be seen within the left kidney as a result of the experiment?

An 80-year-old man is evaluated after a syncopal episode.  He has had recurrent episodes of lightheadedness upon standing from a sitting or lying position for the past several weeks.  Medical history is significant for Parkinson disease.  The patient undergoes tilt-table testing during which his blood pressure and heart rate are continuously monitored at supine and upright positions.  The results are shown below:

Which of the following is the most likely cause of this patient’s current condition?

A 33-year-old woman comes to the office to discuss lesions on her scalp and face.  The patient has had these lesions for several months and describes them as itchy.  She has no other medical conditions and takes no medications.  The patient does not smoke and drinks 3 or 4 alcoholic beverages a night on the weekends.  Vitals signs are within normal limits.  A picture of the skin lesions is shown below.

Which of the following cells is primarily involved in the pathogenesis of this patient’s skin lesions?

A 76-year-old man with a history of bicuspid aortic valve develops fever, chills, and fatigue 2 weeks after cystoscopy with bladder biopsy.  Physical examination shows a new early diastolic murmur at the left upper sternal border.  Echocardiography reveals aortic valve vegetations.  The patient is diagnosed with infective endocarditis.  Blood cultures grow Enterococcus faecalis.  Antibiotic sensitivity testing shows that the organism is resistant to moderate levels of gentamicin.  However, when the bacteria is pretreated with penicillin and subsequently exposed to gentamicin, a rapid bactericidal effect is observed.  Which of the following is the most likely mechanism of gentamicin resistance in this bacterial isolate?

A 36-year-old woman with a history of obesity comes to the office for follow-up.  She has failed to lose weight with dietary intervention and exercise and says that her exercise capacity is limited by knee pain.  The patient has a family history of diabetes mellitus.  Her BMI is 37 kg/m² and physical examination is unremarkable.  Her HbA1c is 5.6%.  The patient is initiated on a medication to help with weight loss.  She is instructed that the medication can cause abdominal discomfort, flatulence, and diarrhea as it inhibits enzymes that break down fat in the intestines.  Which of the following medications was most likely prescribed to this patient?

A 76-year-old man comes to the office with lower extremity edema and recent weight gain.  He has smoked two packs of cigarettes daily for the past 40 years.  Chest x-ray shows a normal-sized heart and a right-sided perihilar mass.  Further evaluation with 24-hour urine collection reveals a urine protein excretion of 5 g/day.  A renal biopsy is performed, and light microscopy of the tissue sample is shown below.

Which of the following is the most likely diagnosis?

A 62-year-old woman comes to the office due to bright red blood in her stool.  She has also had a persistent sensation of rectal pressure, progressive constipation, anorexia, and weight loss of 4.5 kg (10 lb) over the past 6 months.  The patient has never had a colonoscopy.  She does not use tobacco or alcohol.  On examination, the liver edge is palpable 3 cm below the right costal margin.  Rectal examination shows a friable mass.  Imaging studies demonstrate several lesions suspicious for metastases in the right and left lobes of the liver but no lesions in the lungs or bones.  Which of the following routes of venous drainage best explains the distribution of metastatic disease in this patient?

A 67-year-old woman is brought to the office by her daughter for evaluation of a skin rash.  She has a pruritic rash on both lower extremities that is worst at the anterolateral right ankle.  She has not used any new soaps, laundry detergents, cosmetics, or cleaning products.  The patient has stayed indoors for the last 4 weeks since she slipped and fell on an icy sidewalk.  Past medical history is notable for hypertension, hypothyroidism, and early dementia.  The patient lives alone with 2 small dogs and does not smoke or drink alcohol.  On physical examination, the skin over her extremities is dry and cracked, as shown in the image below.

Which of the following is the best advice for this patient?

A 12-year-old boy is evaluated in the clinic due to several episodes of red urine discoloration and muscle soreness while playing soccer.  The patient’s thigh and back muscles become stiff and painful a few minutes after he begins playing.  He often needs to rest for about 10 minutes before the discomfort improves, but afterward he can finish the remainder of the game without further pain or stiffening.  The patient is upset because the symptoms are interfering with his performance, and his team has an upcoming tournament.  Vital signs are normal.  Examination is unremarkable.  Skeletal muscle biopsy in this patient would most likely show high intracellular content of which of the following substances?

A 14-year-old girl comes to the emergency department with confusion and vague abdominal pain.  She also has had polyuria and unintentional weight loss for the last few weeks.  Past medical history is unremarkable, but the patient’s mother has type 1 diabetes treated with an insulin pump.  On examination, the patient’s mucous membranes are dry and her breath has a fruity odor.  Laboratory evaluation shows elevated serum glucose, low serum bicarbonate, elevated anion gap, and elevated serum ketones.  She is started on high-flow intravenous fluids and an infusion of regular insulin.  As a result of this intervention, the concentration of which of the following substances is expected to increase sharply in liver cells?

An investigator isolates an integral membrane receptor.  X-ray crystallography reveals that the receptor is a large protein composed of 7 transmembrane helical domains connected by intracellular and extracellular loops, with an extracellular amino terminus and intracellular carboxyl terminus, as represented in the image below.

These transmembrane domains, which interact strongly with the inner core of the membrane phospholipids, most likely contain of which of the following amino acids?

A 32-year-old man returns to the hospital due to facial pain and nasal congestion.  The patient was recently discharged after being treated for diabetic ketoacidosis.  He says, “It’s just my luck to get sick with a head cold right after I get out of the hospital.”  The patient was diagnosed with type 1 diabetes mellitus at age 16 and has since had several episodes of diabetic ketoacidosis.  His temperature is 38.3 C (101 F), blood pressure is 132/88 mm Hg, pulse is 82/min, and respirations are 12/min.  On physical examination, right eye movement is moderately restricted, and necrotic destruction of the nasal turbinates with thin bloody nasal discharge is present.  This patient’s disease process is most likely to involve which of the following dural sinuses?

A 3-month-old male is brought to clinic for a routine check-up.  His parents recently emigrated from Eastern Europe.  The baby is exclusively breast-fed and receives vitamin D supplementation.  The mother complains that the baby “turns blue” each time he cries.  When the episodes last a long time, he gets very agitated and gasps for breath.  Which of the following is most likely responsible for this infant’s symptoms?

A 24-year-old man comes to the clinic due to a 3-day history of fever and progressive facial swelling.  Medical history is unremarkable, but he did not receive the usual childhood vaccinations.  The patient is sexually active with 2 partners and uses condoms inconsistently.  Temperature is 39.6 C (103.3 F).  Examination shows swelling and tenderness in the parotid glands bilaterally, with local edema obscuring the angles of the mandible.  There is no dysphagia or odynophagia.  The patient is treated with nonsteroidal anti-inflammatory drugs, and his initial symptoms resolve.  However, he returns 2 months later and says he does not “feel like having sex.”  Which of the following treatments is most likely to help this patient?

A 26-year-old man comes to the emergency department due to abdominal pain and diarrhea.  He has had 5-7 bowel movements daily for the past week.  Appetite has decreased.  The patient does not use tobacco, alcohol, or recreational drugs.  He has had 2 male sexual partners in the past year.  Temperature is 37.8 C (100 F), blood pressure is 124/72 mm Hg, pulse is 104/min, and respirations are 18/min.  Examination of fresh stool shows occasional trophozoites with phagocytosed red blood cells.  Which of the following pathogens is the most likely cause of this patient’s disease?

A 70-year-old man is brought to the office by his daughter due to abnormal movements.  The daughter says, “I get to visit my dad only twice a year, and this time I’ve noticed he’s been wincing a lot—he says he isn’t in any pain though.”  The patient has a history of hypertension and schizophrenia, both well controlled for years with medication.  Physical examination shows lip puckering and smacking, facial grimacing, and choreiform movements of the extremities.  There is no focal muscle weakness or rigidity.  Which of the following is the most likely cause of this patient’s abnormal movements?