A 43-year-old man presents for a routine check-up.  He has no current complaints.  His family history is significant for diabetes mellitus in his mother and a heart attack in his father at age 54.  In the office today, the patient’s blood pressure is 146/92 mmHg and his heart rate is 86/min.  His BMI is 36 kg/m². Laboratory findings are shown below:

Item 1 of 2
Starting this patient on simvastatin would most likely increase which of the following?

Item 2 of 2

Some of the lipoprotein particles in this patient’s plasma contain an apoprotein with 48% of the total amino acids found within the coding region of the ApoB gene.  This truncated protein is the result of post-transcriptional modification of the ApoB mRNA transcript.  Which of the following cell types are most likely involved in the synthesis of this truncated protein?

A 25-year-old healthy woman participates in a clinical study.  Vital signs and physical examination prior to the experiment are normal.  During the study, the subject drinks 2 L of distilled water over 10 minutes.  Over the next few hours, aquaporin-2 channels are most likely to be predominantly found in which of the following nephron locations?

A 43-year-old man comes to the office due to increasing discomfort and pain with sitting over the past several months.  He also has had occasional perianal pruritus.  Physical examination shows multiple, cauliflower-shaped verrucous growths measuring 1-2 cm on the perianal skin.  Histopathologic examination of one of the lesions reveals hyperplastic papillary squamous epithelium with hyperkeratosis, nuclear irregularity, and perinuclear halos of cytoplasmic vacuolization.  Which of the following additional studies is most appropriate for this patient at this time?

A 62-year-old man undergoes biopsy of a suspicious skin lesion on his left forearm.  The instrument tray used for the biopsy was prepared by a new, unexperienced medical assistant.  After the procedure, the physician discovers that the assistant prepared the tray using clean but unsterilized instruments from a previous procedure.  The physician immediately notifies the patient and apologizes for the error.  After hearing about the error, the patient shouts, “I don’t understand how this could have happened.  What if the person you used those instruments on has HIV?  You shouldn’t be allowed to practice medicine if you can’t keep your patients safe!” Which of the following is the most appropriate response to this patient?

A 6-week-old boy is brought to the office with a rapidly growing skin lesion on his cheek.  Physical examination findings are shown in the image below:

Histopathologic examination of the lesion would most likely show which of the following features?

A 36-year-old woman comes to the clinic for follow-up of HIV infection.  The patient was diagnosed with HIV approximately 15 years ago.  She had been taking combination antiretroviral therapy until 5 months ago when she had a mental breakdown triggered by the sudden death of her husband.  The patient’s CD4⁺ T-lymphocyte count has been consistently >750/mm³, and her peripheral blood HIV RNA has been undetectable.  However, repeat studies today show that her CD4⁺ count is now 310/mm³ and her HIV RNA is 8,212 copies/mL.  Reactivation of HIV from which of the following reservoirs most likely explains this patient’s viremia?

A 24-year-old man comes to the office due to a nagging cough following an upper respiratory tract illness 4 weeks ago.  The cough is gradually improving but continues to disturb his sleep and interfere with his work.  The patient does not use tobacco, alcohol, or recreational drugs.  He takes no prescription medications.  Vital signs are normal.  On physical examination, nasal and oropharyngeal mucosa are normal.  The lungs are clear on auscultation.  The patient recently started taking over-the-counter dextromethorphan and says it has helped a little.  This medication is most likely to provide symptom relief through which of the following mechanisms?

A 35-year-old woman comes to the emergency department due to a 4-day history of fever, abdominal pain, and profuse diarrhea.  The patient also has nausea and vomiting.  She is a chef and frequently tastes food while cooking.  The patient has no chronic medical conditions and takes no medications.  She has not traveled recently.  Temperature is 38.8 C (101.8 F), blood pressure is 110/70 mm Hg, and pulse is 100/min.  Abdominal examination shows mild, diffuse tenderness.  Bowel sounds are increased.  Examination of the stool shows numerous leukocytes.  Stool is positive for occult blood.  Which of the following is the most likely pathogen?

A study was conducted to determine the association between exposure to a hazardous chemical and death/disability.  The study population included individuals who were employees of a chemical company when the company had a chemical accident 10 years ago.  The researchers used company records to identify a group of employees who were exposed to the hazardous chemical during the incident and another group of employees who remained unexposed.  Government databases were subsequently searched to determine the status (eg, alive, deceased, disabled) of individuals in both groups.  Which of the following study designs best describes this research investigation?

An 85-year-old woman is brought to the emergency department due to an episode of syncope and generalized weakness.  Her pulse is noted to be 30/min.  The patient is not taking any medications.  ECG shows atrial fibrillation with advanced atrioventricular block and occasional conduction of atrial impulses to the ventricles.  She undergoes placement of a pacemaker with a single pacing lead in the right ventricle.  Postoperative ECG is shown in the exhibit; arrows indicate the pacing stimuli generated by the device.  Which of the following best describes the pacemaker function in this patient?

A 74-year-old man comes to the office due to Parkinson disease.  He has been taking carbidopa-levodopa for 8 weeks.  The patient has noticed moderate improvement in his condition.  However, he decided to take extra doses on his own in an effort to improve his symptoms even further.  Which of the following adverse effects is most likely to result from this increase in dosage?

Researchers are studying a specific gene in rats.  This gene has 2 allelic variants, A and C.  Rats with the AA and AC genotypes manifest the dominant trait, and rats with the CC genotype develop the recessive trait.  In a population of 300 rats, the researchers observe the genotype distribution shown below.

Which of the following represents the frequency of the C allele currently in this population?

A 62-year-old woman comes to the office due to vision disturbances.  For the past 6 weeks, the patient has had blurry vision, which she describes as “looking through dirty glasses.”  There is no associated eye pain, redness, discharge, or headache.  Medical history includes hypertension controlled with life-style modification; dermatomyositis treated with prolonged prednisone therapy; and Crohn disease, which has required multiple bowel resections.  The patient is a retired swimming pool lifeguard; she has a 30-pack-year smoking history but quit 10 years ago.  Blood pressure is 126/72 mm Hg and pulse is 78/min.  Ocular examination shows normal conjunctivae and cornea, and no opacities in the lenses.  Funduscopy reveals an increased cup/disc ratio with no other retinal abnormalities.  Automated visual field testing reveals decreased peripheral vision in all axes bilaterally.  Which of the following most likely contributed to this patient’s current condition?

A 63-year-old man comes to the office for follow-up one month after a stroke that resulted in speech difficulties.  He says that he is improving: “I can understand everything, but I still have trouble talking with people I don’t mow…  I mean show, no slow!  I’m so frustrated because I know what I want to say but I just can’t say it night!”  The patient’s speech is fluid with appropriate cadence, but he is unable to correctly repeat phrases that the physician verbalizes.  He can follow 2- and 3-step commands without difficulty.  Which of the following brain regions is most likely impaired in this patient?

A 13-year-old, previously healthy boy is brought to the office due to progressively worsening throat pain over the last 4 days.  He also reports malaise and decreased oral intake.  The patient has no vomiting or diarrhea.  Vaccinations are up to date.  The voice sounds muffled.  Temperature is 38.8 C (101.8 F).  The patient has difficulty opening the mouth due to pain.  The right tonsil is markedly enlarged and fluctuant, and the uvula is deviated to the left.  Which of the following is the most likely diagnosis?

A 17-year-old boy comes to the office due to a skin rash that has been present for a day.  One week ago, he had a sore throat that improved with oral penicillin therapy.  Skin examination shows several violaceous, raised, nonblanchable lesions distributed over the bilateral lower extremities.  Histologic findings of the biopsied rash are shown in the image below.

Which of the following is the most likely diagnosis?

A 29-year-old man comes to the office to participate in a research study for recurrent respiratory papillomatosis, a human papillomavirus (HPV)–mediated disease.  The patient has required multiple surgical debridements in the past, and biopsy results have shown benign cells with HPV-11 infection.  The disease has recently progressed to involve the trachea and bronchi, leading to 2 episodes of postobstructive pneumonia.  As part of the research study, the patient will receive avelumab, a programmed cell death protein ligand 1 (PD-L1) immune checkpoint inhibitor.  This medication most likely exerts its therapeutic effect through which of the following mechanisms?

A newborn boy delivered 2 hours ago is evaluated for cyanosis.  Physical examination is significant for cyanosis of the upper and lower extremities, the trunk, and the mucous membranes.  S1 is widely split, and there is a 2/6 holosystolic murmur best heard at the left lower sternal border that increases in intensity with inspiration.  Pulses are 1+ and equal in all extremities.  The lungs are clear to auscultation.  Chest x-ray reveals an enlarged heart.  Which of the following is most likely present in this patient?

A 67-year-old man is brought to the emergency department by ambulance due to altered mental status.  He was having dinner with his daughter when he suddenly became confused and slumped over.  The patient has a history of atrial fibrillation for which he takes an oral anticoagulant.  He is widowed and lives with his daughter.  Blood pressure is 208/113 mm Hg, pulse is 64/min and irregular, and respirations are 15/min.  Oxygen saturation is 88% on room air.  The patient is obtunded and unable to follow commands.  Pupils are midsized and unresponsive to light.  The physician determines that intubation is necessary at this time to protect the patient’s airway and asks for consent from the daughter and older son who are at the bedside.  They tell the physician that the patient does not have an advance directive and that they are unsure how to proceed.  Which of the following is the most appropriate next step in decision-making for this patient?

A 25-year-old man comes to the fertility clinic for evaluation.  The patient and his wife have been trying to conceive for the past year without success.  Vital signs are normal.  Examination shows a normal-sized penis with small-volume testicles.  There is mild gynecomastia bilaterally.  Imaging reveals the presence of seminal vesicles and vas deferens.  Semen analysis shows azoospermia, and laboratory evaluation reveals elevated FSH and LH with low serum testosterone levels.  A karyotype is obtained, revealing 46,XX.  Which of the following is the most likely diagnosis?

A 70-year-old woman comes to the emergency department due to severe back pain.  It started 4 hours ago after a sudden jolt when the patient drove over a large pothole.  She has no previous history of back pain or major trauma.  The patient has otherwise been feeling well.  She has no significant chronic medical conditions and takes no medications.  She drinks alcohol socially and does not use tobacco or recreational drugs.  The patient underwent menopause at age 50.  Vital signs are within normal limits.  BMI is 18.9 kg/m².  On examination, there is point tenderness over the T10 vertebra.  Neurologic examination is unremarkable.  The remainder of the examination shows no abnormalities.  Imaging reveals a T10 compression fracture but appears otherwise normal for her age.  Which point on the graph below most likely corresponds to this patient’s metabolic state immediately prior to the fracture?

A 26-year-old man comes to the office due to myalgia, nasal congestion, and cough.  Temperature is 38.3 C (100.9 F).  Examination shows nasal and pharyngeal hyperemia.  Rapid influenza antigen testing of nasopharyngeal secretions is positive.  Within the infected cells of the patient’s respiratory tract, viral proteins are degraded and attached to major histocompatibility complex class I molecules, which are then expressed on the cell surface for presentation to cytotoxic CD8⁺ lymphocytes.  Which of the following enzymes is most essential to ensuring the initiation of this immune process?

A 67-year-old man is hospitalized for a new diagnosis of decompensated heart failure.  Echocardiography during hospitalization showed no valvular dysfunction and left ventricular dilation with an ejection fraction of 30%.  Coronary angiography showed nonobstructive coronary artery disease.  After undergoing treatment with intravenous diuretics for several days the patient is being prepared for discharge.  Blood pressure is 125/80 mm Hg and pulse is 67/min and regular.  The lungs are clear to auscultation and he has no peripheral edema.  The plan is made to initiate sacubitril-valsartan.  The patient should be specifically educated on which of the following adverse effects?

A 45-year-old woman with systemic lupus erythematosus (SLE) comes to the office for a checkup.  The patient’s symptoms are mild and well controlled with nonsteroidal anti-inflammatory drugs.  She was recently fired from her job due to showing up late for work daily despite repeated warnings from her boss.  Although the patient previously enjoyed her job, she now says she would have resigned anyway as the job was not really satisfying.  She hopes to use her extra time to write a book to help others living with SLE.  Which of the following best explains this patient’s behavior?

A 47-year-old woman comes to the office for follow up of chronic asthma.  The patient was recently hospitalized for an asthma exacerbation and required a prolonged period of mechanical ventilation as well as nebulized bronchodilators and intravenous glucocorticoids.  Her symptoms improved, and she was discharged on oral prednisone.  The patient reports compliance with therapy.  She has no other medical conditions and takes no other medications.  Blood pressure is 128/72 mm Hg, pulse is 85/min, and respirations are 18/min.  On physical examination, there is mild expiratory wheezing.  Because of the persistent respiratory findings, the patient is continued on the same treatment regimen.  Long-term administration of this oral therapy is most likely to increase which of the following in this patient?

A 4-week-old infant is evaluated for frequent episodes of hypoglycemia.  The patient is found to have elevated insulin levels during periods of fasting.  Several members of his family have a similar condition.  Genetic testing reveals a mutation involving potassium channels expressed in pancreatic beta cells.  The mutated channels have a higher sensitivity to the substance that normally modulates their activity, causing increased beta cell secretory activity.  Which of the following substances normally binds to and regulates the ion channels that are responsible for this patient’s hypoglycemia?

A 13-year-old boy is brought to the clinic due to breast development.  Two months ago, the parents first noticed bilateral breast buds, which have slowly enlarged.  Height is 151 cm (59.4 in) and weight is 37.5 kg (82.7 lb), corresponding to the 25th and 15th percentiles, respectively.  BMI is at the 16th percentile.  Temperature is 37 C (98.6 F), blood pressure is 106/64 mm Hg, pulse is 90/min, and respirations are 16/min.  Breast palpation reveals bilateral concentric, mobile, tender mounds of tissue deep to the areolas, one measuring 1.5 cm in diameter and the other measuring 2.5 cm.  Genital examination is consistent with sexual maturity rating (Tanner stage) 1.  Which of the following clinical features in this patient is most concerning for a pathological cause of the breast enlargement?

An 18-month-old child is brought to the office for evaluation of delayed walking and lower limb deformity.  The mother has short stature and underwent corrective surgery for bowed legs when she was an adolescent.  Vital signs are within normal limits.  Examination shows delayed developmental milestones for gross motor function but age-appropriate findings for social function, vision, speech, and hearing.  Musculoskeletal examination reveals widening of the knee joints with significant bowing of the legs.  Serum laboratory results are as follows:

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

A microbiologist performs a genetic experiment in which cultures of Escherichia coli are treated with a chemical that induces a high frequency of mutations.  Individual bacterial colonies are isolated to identify a mutant strain that lacks a specific enzyme involved in DNA replication.  This specific enzyme is responsible for removing short fragments of RNA that are base paired to the DNA template.  Which of the following enzymes is most likely deficient in this strain of E coli?

A 5-year-old boy is brought to the office by his parents for evaluation of headaches and difficulty walking.  The headaches occur in the early morning and are accompanied by vomiting.  The mother says the boy has become “very wobbly on his feet” over the past 2 weeks.  Physical examination is notable for an ataxic gait.  MRI of the brain reveals a solid, midline posterior fossa mass.  Biopsy of the mass demonstrates sheets of small basophilic cells with several mitotic figures.  Which of the following is the most likely diagnosis?

A physician is approached by a friend who requests a prescription for antidepressant medication.  The physician has been friends with this individual since college and is aware that she has been treated for depression in the past.  The friend explains that she is only “a little depressed” due to work stress and relationship issues and would like to resume sertraline, which she has taken previously.  She has a physician but wants to avoid seeing the provider due to difficulty getting an appointment and her own busy schedule.  Which of the following is the most appropriate response?

An 18-year-old man comes to the office due to progressively worsening fatigue.  He returned yesterday from a week-long international trip, during which he provided aid in a rural region of a resource-limited country.  While there, the patient developed frequent diarrhea that contained blood and mucus.  He took ciprofloxacin for several days, and the diarrhea resolved.  Yesterday, the patient noted fatigue and shortness of breath with exertion.  Temperature is 37.1 C (98.8 F), blood pressure is 116/70 mm Hg, and pulse is 112/min.  Physical examination is remarkable for scleral icterus.  Mucous membranes are pale but moist.  Cardiopulmonary examination demonstrates mild tachycardia.  The abdomen is soft and nontender without organomegaly.  Laboratory results are as follows:

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

A 26-year-old man comes to the emergency department due to fever, right flank pain, and difficulty walking for the past 3 days.  A week ago, the patient was treated with cephalexin for bacterial folliculitis.  He was diagnosed with type I diabetes mellitus 10 years ago and takes subcutaneous insulin.  Temperature is 38.9° C (102° F).  During the medical interview, the patient lies supine on the examination table with his right hip and knee flexed and the limb externally rotated.  On physical examination, he resists passive extension at the right hip due to worsening of the pain.  This patient’s pathological process most likely involves which of the following muscles?

A 47-year-old man comes to the office due to worsening shortness of breath for several months.  The patient has no fever, weight loss, or cough.  He has no other medical conditions and takes no medications.  The patient does not use tobacco, alcohol, or illicit drugs.  Vital signs are normal.  Pulmonary examination demonstrates wheezing and poor air movement.  Laboratory results are as follows:

A liver biopsy is subsequently performed.  Light microscopy of the tissue specimen after treatment with diastase and periodic acid–Schiff staining is shown in the exhibit.  Given these findings, which of the following is the most likely cause of this patient’s shortness of breath?

A prospective cohort study was conducted to describe the association between admission to an intensive care unit (ICU) in different areas of the world and subsequent development of sepsis.  Adults (age ≥21) admitted to an ICU during a specific period were enrolled in the study.  Data were collected daily, and outcomes were recorded until discharge, death, or a maximum of 60 days.  Preliminary results showed that patients admitted to ICUs in North America were 35% less likely to develop sepsis than patients admitted to ICUs in South America.  Based on this result, which of the following would be the correct value of the risk ratio (RR) for sepsis in North America compared to South America?