A 32-year-old man comes to the office due to a subcutaneous nodule on the dorsum of his right hand.  He says the nodule is painless and has been slowly enlarging over the last several weeks.  The patient’s past medical history is insignificant, but his father died of a heart attack at age 38 despite being a nonsmoker.  His mother has diabetes mellitus.  On examination, he has 2 or 3 small, flat subcutaneous nodules on the dorsum of his right hand, and a larger nodule at the Achilles tendon area.  He also has a few small yellowish papules on his right lower eyelid.  Which of the following is most likely decreased in this patient?

A 52-year-old man comes to the clinic with frequent mid-abdominal pain.  He describes the pain as gnawing.  It wakes him during the night and can be relieved by eating a light meal.  The patient has also been using over-the-counter ibuprofen for relief.  Three weeks ago, he was started on omeprazole with some improvement of his symptoms.  Medical history is insignificant.  The patient works as a missionary and travels across the country and abroad.  He does not use tobacco or drink alcohol.  The abdomen is mildly tender on deep palpation in the epigastric area.  There is no rebound tenderness or rigidity.  Urea breath test is negative.  Upper gastrointestinal endoscopy is performed and reveals a duodenal ulcer.  Gastric biopsies are consistent with Helicobacter pylori infection.  Which of the following best explains the negative urea breath test in this patient?

A 52-year-old immigrant from Eastern Europe presents to the outpatient clinic complaining of dyspnea on exertion that has been increasing in severity over the past several weeks.  She also describes nocturnal dyspnea and a cough that occasionally produces blood-tinged sputum.  When the patient lies in the left lateral decubitus position and exhales fully, you hear a low-pitched, mid-diastolic murmur at the cardiac apex.  Which of the following most likely underlies her condition and symptoms?

A 12-year-old boy is brought to the office after developing bloody stools.  He is adopted and his family history is unknown.  Vital signs are within normal limits.  Physical examination reveals conjunctival pallor and blood-streaked stool within the rectal vault.  The patient’s lips are shown in the image below:

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

A 44-year-old man comes to the office due to a tender mass in the right buttock that has progressively expanded over the past several months.  He has no known past medical history.  Temperature is 37.1 C (98.8 F).  Examination reveals a well-circumscribed 9 x 5 cm mass involving the right buttock area.  A biopsy of the lesion is performed.  Histopathology reveals many round cells with multiple mitoses.  Some cells have round clear cytoplasmic vacuoles scalloping the nucleus.  Which of the following is the most likely diagnosis in this patient?

A 62-year-old man comes to the office due to skin lesions on his trunk and extremities for the past 2 weeks.  He has bullae that rupture easily, particularly in areas exposed to regular friction, and subsequently become painful erosions.  He also has painful sores in his mouth.  On examination of the skin, several flaccid bullae are noted; they extend laterally into surrounding skin with direct pressure.  Large areas of erosion also are present in the oral cavity.  Histologic analysis of the patient’s skin will most likely show immunoglobulin deposits in which of the following locations?

A 1-hour-old boy is admitted to the neonatal intensive care unit due to respiratory distress.  The patient was born via cesarean delivery to a 34-year-old mother with a 10-year history of poorly controlled type 1 diabetes mellitus.  Weight is 4.7 kg (10 lb 6 oz).  Pulse oximetry shows 78% on room air.  Examination immediately after delivery shows tachypnea, nasal flaring, and intercostal retractions.  The patient is intubated, and mechanical ventilation is started.  High pressures are required to achieve normal tidal volume and keep the alveoli inflated due to a primary dysfunction involving a specific cell type found within the pulmonary epithelium.  This type of cell also has which of the following additional functions?

A 65-year-old man comes to the office due to persistent right shoulder pain and right hand clumsiness.  The patient has noticed difficulty picking up objects with the right hand when working in his garage.  His wife adds that he has been coughing excessively for the past several months but refuses to quit smoking.  The patient has smoked 1½ packs of cigarettes daily for 40 years.  On physical examination, the eyes are asymmetric and have anisocoria.  The right shoulder is unremarkable, but there is weakness of the intrinsic muscles of the right hand.  There is no weakness or sensory loss in other extremities.  Chest x-ray is shown in the image below:

This patient’s ocular findings are most likely caused by damage to which of the following structures?

A 46-year-old homeless man with a long history of severe alcohol use disorder comes to the emergency department due to frequent falls over the last 2-3 weeks.  He has made attempts to cut down on his drinking, but the falls have continued.  In addition to “feeling unsteady,” he notes occasional blurred vision.  The patient does not use illicit drugs.  Review of hospital records reveals previous admissions for pancreatitis, severe gastritis, and alcohol withdrawal.  Physical examination reveals a coarse, rhythmic, postural tremor affecting his fingers and arms.  This finding is most likely the result of pathology involving which of the following brain structures?

A 27-year-old woman with a history of depression is hospitalized for an episode of elated mood, poor sleep, and agitation.  The patient has a family history of mood disorder.  She is started on the appropriate treatment and discharged from the hospital.  Four weeks later, the patient reports feeling better and resumes regular activities.  However, she also reports excessive thirst and dry mouth.  On examination, her blood pressure is 110/80 mm Hg and pulse is 84/min.  Mucous membranes appear dry.  Urine specific gravity is <1.003.  No significant change is seen after 4 hours of water deprivation.  Which of the following is the most likely cause of this patient’s current symptoms?

A previously healthy 2-year-old boy is brought to the emergency department by his parents due to brisk rectal bleeding that began 1 hour ago.  The patient received antibiotics once for an ear infection 2 months ago but has otherwise been healthy and takes no medications.  Family history is significant for a maternal uncle with inflammatory bowel disease.  The patient’s weight is at the 75th percentile and height is at the 50th percentile.  Temperature is 37.2 C (99 F), blood pressure is 90/60 mm Hg, and pulse is 112/min.  Physical examination of this well-appearing boy shows a soft, nontender abdomen with normoactive bowel sounds.  Laboratory results are as follows:

Which of the following is the most likely pathophysiologic cause of the patient’s bleeding?

A 32-year-old man comes to the office with chest pain.  He describes the pain as a tightness or pressure that occurs when he walks uphill, runs, or climbs stairs.  The pain subsides with rest.  The patient also experiences occasional episodes of light-headedness on exertion.  He has no history of palpitations, syncope, or lower extremity swelling.  His uncle collapsed and died while playing basketball at age 34.  Physical examination reveals a systolic murmur along the left sternal border that intensifies upon standing.  Which of the following additional findings is most likely to be seen in this patient?

A 52-year-old woman comes to the office due to occasional chest discomfort and exertional dyspnea.  Medical history is significant for hypertension.  There is a strong family history of coronary artery disease.  ECG shows normal sinus rhythm with right bundle branch block.  There are no heart murmurs on auscultation.  A widely split heart sound is heard at the upper sternal border and is accentuated by inspiration.  On cardiac catheterization, which of the following points is most likely to correspond with the early component of the split heart sound?

A 5-year-old boy is brought to the clinic with fever and ear pain that developed this morning.  He has no ear drainage or other symptoms.  Review of the patient’s medical record shows several episodes of sinusitis and otitis media and an episode of pneumococcal pneumonia that required intensive care.  The patient has been growing along the 60th percentile for both weight and height.  Physical examination reveals a well-appearing boy with bilateral, bulging, erythematous tympanic membranes.  Laboratory results are as follows:

Which of the following is the most likely diagnosis?

An experimenter develops a cell-free in vitro DNA replication system to closely study the events of the prokaryotic cell cycle.  First, several enzymes and protein factors felt to be necessary for the replication process are purified from a bacterial extract.  These enzymes and factors are then incubated with the complete genomic DNA of Escherichia coli.  The experimenter finds that one of the replicated DNA strands is formed continuously, whereas the other consists of multiple discontinuous DNA fragments with intervening oligomers of RNA.  The addition of which of the following enzymes to this system is most likely to result in removal and replacement of these RNA oligomers with DNA?

Investigators plot sensitivity against (1 – specificity) for several diagnostic tests used as biomarkers for sepsis.  Which of the tests shown below is most accurate in diagnosing sepsis?

A 54-year-old woman comes to the office due to abdominal distension and discomfort for the past 4 months.  She also has poor appetite and occasional nausea without vomiting.  Her last menstrual period was 5 years ago.  The patient’s younger sister has a history of colon cancer, and her mother died of endometrial cancer.  Physical examination shows a distended, nontender abdomen and adnexal fullness on the right.  Ultrasound reveals free fluid in the peritoneal cavity along with a right ovarian mass.  CA-125 levels are elevated.  What is the most likely molecular mechanism responsible for this condition?

A 53-year-old man comes to the office due to anorexia, nausea, and weakness.  The patient has a history of chronic hepatitis C, type 2 diabetes mellitus, hypertension, and dilated cardiomyopathy for which he underwent a cardiac transplantation a year ago.  Blood pressure is 150/90 mm Hg and pulse is 78/min.  Cardiopulmonary examination shows normal heart sounds and vesicular breath sounds.  There is no rash.  Laboratory evaluation reveals that blood urea nitrogen is 56 mg/dL and serum creatinine is 3.8 mg/dL.  Laboratory values were normal a month ago.  Urinalysis is unremarkable.  Renal biopsy is performed, and light microscopy demonstrates obliterative vasculopathy of the afferent arterioles.  Which of the following medications is most likely responsible for this patient’s current presentation?

A 62-year-old man comes to the emergency department due to 8 hours of mild fever, vomiting, and worsening abdominal pain.  The patient has had chronic epigastric pain for several months.  Medical history is significant for hypertension and Parkinson disease.  Physical examination shows a diffusely tender abdomen without rebound or guarding.  Cardiopulmonary examination is unremarkable.  A nasogastric tube is placed and brown fluid is aspirated.  Which of the following parenteral medications must be avoided while treating this patient’s acute condition?

A 2-year-old girl is brought to the office for evaluation of black stains on her cloth diapers that have occurred several times over the past few days.  These stains seem to occur after a wet diaper is not changed immediately, such as when she is playing outside.  The patient has normal, soft bowel movements every other day and no other symptoms.  She has been growing and developing well.  The patient takes no medications and has no allergies.  Her father was recently diagnosed with tuberculosis and is on appropriate therapy.  The patient’s vital signs are normal, and physical examination shows no abnormalities.  Which of the following complications will this patient most likely experience?

A 67-year-old man is evaluated due to slowing of his gait.  His wife reports that he now takes longer to complete his evening walk than he did a year ago.  The patient has a history of hypertension and hyperlipidemia, and his father died at age 70 due to stroke.  Physical examination shows increased resistance to passive elbow flexion and extension and a hand tremor that disappears with movement.  Which of the following labeled structures on the below brain MRI is most likely to be involved in this patient’s condition?

A patient with a long history of atrial fibrillation experiences right foot pain.  He presents to the emergency department four hours after the onset of the pain.  Physical examination reveals a pale, cold right foot without a palpable pulse over the dorsalis pedis artery.  Which of the following is most likely increased in the extracellular space of the affected region?

Immunohistochemistry staining of a rat kidney section reveals a blackened region of protein accumulation (as indicated by a white arrow in the image below).

Which of the following proteins is most likely demonstrated by this special stain?

A 28-week-gestation infant dies of respiratory failure 24 hours after birth despite aggressive resuscitative measures.  An autopsy is performed, and microscopy of the patient’s lung tissue is shown below:

Which of the following is the most likely primary cause of these findings?

A 24-year-old woman comes to the emergency department due to back pain after falling in the shower.  The patient has no prior medical conditions and does not use tobacco, alcohol, or recreational drugs.  She is a professional long-distance runner and has participated in several competitions.  Family medical history is significant for colon cancer in her father and hypothyroidism in her mother.  Temperature is 36.7 C (98 F), blood pressure is 130/80 mm Hg, and pulse is 92/min.  On physical examination, focal midline tenderness is noted over the lower thoracic spine.  Bilateral lower extremity motor strength, sensation, and deep tendon reflexes are normal.  Spine imaging reveals a fracture of the T10 vertebral body.  Which of the following is the most likely underlying mechanism responsible for this patient’s current condition?

A 10-year-old boy is brought to the office for visual problems.  His mother reports that over the past 3 months, he has been sitting close to the television due to difficulty seeing.  The patient has also been squinting at the board at school.  Past medical history is notable for mild intellectual delay for which he receives extra assistance in school.  He has 4 older siblings, one of whom had a sagittal sinus venous thrombosis at age 12.  Weight is at the 25th percentile, and height is at the 95th percentile.  Physical examination shows elongated limbs and anterior protrusion of his sternum and ribs.  Ophthalmologic evaluation shows an inferiorly dislocated lens in the right eye.  Which of the following is the most likely cause of this patient’s condition?

A 64-year-old man is evaluated for abdominal pain.  The patient has a history of hypertension and gastroesophageal reflux disease.  He has smoked a pack of cigarettes daily for the last 45 years.  His temperature is 37.2 C (99 F), blood pressure is 140/90 mm Hg, and pulse is 98/min.  BMI is 27 kg/m².  On physical examination, the patient’s abdomen is mildly distended and tender with bowel sounds heard in all 4 quadrants.  Contrast-enhanced CT scan of the abdomen is performed, and results are shown in the image below.

The abnormal structure marked by the asterisk is most likely the result of which of the following processes?

A 19-year-old woman is evaluated for fever, headache, and new-onset seizure.  MRI of the head shows an abnormal signal in the temporal lobe.  Encephalitis caused by herpes simplex virus (HSV) is suspected.  A lumbar puncture is performed for viral polymerase chain reaction (PCR) testing.  In this test, viral DNA is extracted from the patient’s cerebrospinal fluid, and the solution is heated to separate the double-stranded DNA into single strands.  Subsequently, oligonucleotide primers, which are complementary to the flanking regions of a specific HSV DNA sequence, are added and allowed to anneal as shown in the image below.  The different primers used in PCR testing are marked by letters.

Functional DNA polymerase and deoxyribonucleoside triphosphates are then added to the mixture.  Which primers are most likely to yield complementary copies of the specific HSV DNA sequence discussed above?

A 24-year-old woman, gravida 1 para 0, at 9 weeks gestation comes to the emergency department due to swelling and pain in her left leg.  The patient has no chronic medical conditions and has had no surgeries.  Her only medication is a prenatal vitamin.  On physical examination, the left calf is larger than the right and tender to palpation.  Ultrasound examination reveals noncompressible deep veins of the left lower extremity suggestive of thrombosis.  The patient is administered heparin.  Compared to warfarin, this medication is safer for use in pregnancy due to which of the following properties?

A 32-year-old HIV-positive man comes to the physician with severe burning during urination.  Physical examination shows a purulent penile discharge.  Microscopy of the discharge specimen shows multiple white blood cells containing intracellular Gram-negative cocci.  Which of the following is the main bacterial factor responsible for establishing infection in this patient?

A 43-year-old man comes to the emergency department due to decreased vision in his left eye.  He had noticed some floaters in that eye a few days ago.  The patient was diagnosed with HIV but does not take any of his medications regularly.  He was hospitalized with Pneumocystis pneumonia 6 months ago.  Temperature is 36.7 C (98.1 F).  Ophthalmologic examination shows white, opaque patches with hemorrhage at the retinal periphery in the left eye.  There is no cardiac murmur.  Which of the following best describes the mechanism of action of the drug to be used to treat this patient’s visual condition?

A 62-year-old man comes to the office due to exertional dyspnea.  He says, “I can’t climb 2 flights of stairs without having to stop and rest.  I wish my breathing was better so I could get out more and didn’t have to be a burden to my daughter.”  He lives on the 4th floor of a walk-up building and relies on his daughter to do most of his shopping and chores.  The patient has smoked heavily for 30 years and been told to quit several times.  He has a family history of heart disease and lung cancer.  The patient says, “I know it affects breathing and causes cancer and all that, but it is too hard to quit.  I like smoking and you only live once.  I might as well enjoy it.”  Physical examination reveals a barrel-shaped chest with decreased breath sounds bilaterally.  Which of the following responses is most likely to help motivate this patient to stop smoking?

A pharmaceutical researcher is in the process of developing a live influenza vaccine.  She obtains nonpathogenic strains of the influenza A virus that contain a hemagglutinin protein lacking the polybasic cleavage site.  The nonpathogenic strain is cultured together with a pathogenic strain.  Following viral replication, some of the viral particles deriving from the nonpathogenic strain are found to have the wild-type hemagglutinin and are capable of infecting respiratory epithelium.  Subsequent progeny of these altered viruses continue to have the same infectivity characteristics.  Which of the following mechanisms best explains the observed phenomenon?

A 13-year-old boy is brought to the office by his parents due to exercise intolerance.  The patient is unable to sprint as far as his classmates due to severe muscle weakness that develops shortly after he starts running.  The weakness is sometimes accompanied by muscle swelling, stiffness, and cramping, particularly following substantial exertion.  The symptoms have failed to improve over the past month despite regular running practice.  BMI is 18.7 kg/m² (50th percentile), and physical examination is within normal limits.  Which of the following processes is most likely to be impaired in this patient?

A 63-year-old man is being evaluated due to progressive weakness involving the upper and lower extremities and subsequent difficulty with ambulation for 3 days.  Today, he was unable to get out of bed and walk.  Medical history is significant for liver cirrhosis and portal hypertension.  His home medications include nadolol and spironolactone.  Blood pressure is 90/60 mm Hg and pulse is 70/min.  Physical examination shows abdominal distension with a prominent fluid shift.  ECG is shown in the image below:

Which of the following is the most likely cause of this patient’s muscle weakness?

A 24-year-old woman comes to the office due to irritability, frequent mood swings, and palpitations.  The patient has had difficulty concentrating, which is affecting her work.  She also has grittiness in her eyes and excessive tearing.  Several of the patient’s friends have remarked that her eyes appear to be bulging.  She has lost 3.63 kg (8 lb) in the past 2 months, and her last menstrual period was 6 weeks ago.  The patient has no medical problems and takes no medications.  She smokes 5 cigarettes a day and does not use alcohol or illicit drugs.  Family history is significant for hypertension in her father.  Blood pressure is 120/60 mm Hg and pulse is 120/min.  Physical examination reveals symmetric proptosis and periorbital edema.  Urine pregnancy test is negative.  Which of the following best explains this patient’s eye symptoms?

A 64-year-old woman comes to the emergency department due to palpitations and progressive exertional dyspnea.  She has had no chest pain, cough, or ankle swelling.  Medical history is significant for hypertension that is treated with hydrochlorothiazide.  Blood pressure is 128/72 mm Hg and pulse is 91/min and irregular.  The lungs are clear on auscultation.  The abdomen is soft and nontender without organomegaly.  ECG shows an irregular rhythm with no P waves.  Which of the following graphs most accurately shows the expected change in this patient’s jugular venous pulse waveform?

A 3-year-old boy whose family immigrated to the United States several months ago is being evaluated due to extreme fatigue and occasional syncope.  His mother says that he has had episodes of agitation and tachypnea since birth; these episodes have progressively worsened to the point that the patient sometimes loses consciousness.  Cardiac examination shows a harsh systolic ejection murmur heard over the left sternal border.  Oxygen saturation is 84% while supine and 91% while squatting.  Which of the following is the most likely diagnosis?

A 24-year-old woman comes to the emergency department due to severe headache, nausea, and vomiting.  She has had episodic headaches for the past several months that have progressively worsened.  The patient has self-treated the pain with over-the-counter analgesics, but her pain has recently become refractory to these medications.  She has no other medical problems.  Further evaluation with brain MRI reveals a mass arising from the structure indicated by the white arrow in the image below.

Which of the following findings is most likely to be seen in this patient?

A 3-year-old boy is brought to the hospital due to 2 days of diarrhea and vomiting.  The child has had 10-12 watery stools over the previous 24 hours and several episodes of vomiting.  He has no prior medical problems and has reached his developmental milestones normally.  His immunization history is incomplete.  Temperature is 38.4 C (101.2 F).  Physical examination shows an alert but irritable and ill-appearing child.  He has tenting of the skin with dry lips and buccal mucosa.  The abdomen is mildly distended and tender.  Infection has caused severe small intestinal mucosal damage.  The patient’s condition improves with supportive measures.  Several weeks later, the architecture of the intestinal epithelium returns to normal.  Gastrointestinal stem cells residing at which of the following locations helped to restore the normal intestinal epithelium in this patient?