All practice questions

Match the following cerebrospinal fluid (CSF) laboratory profiles with their most likely corresponding clinical diagnosis.

A 55-year-old man comes to the clinic for a follow-up visit. He has a history of major depressive disorder and hypertension. His medications include paroxetine, which he has been taking for 2 years with excellent symptom control. Two weeks ago, his primary care physician started him on metoprolol succinate for poorly controlled blood pressure. Today, the patient reports severe fatigue, lightheadedness, and episodes of feeling "close to passing out" when standing up quickly. Vital signs show a blood pressure of 98/60 mm Hg and a pulse of 44/min. Physical examination is unremarkable except for bradycardia. An electrocardiogram shows sinus bradycardia with no other abnormalities. Which of the following pharmacokinetic or pharmacodynamic interactions best explains this patient's current presentation?

While rounding in the oncology unit, a physician is urgently called to evaluate a patient who developed abrupt-onset dyspnea and profound lightheadedness. The patient has a history of advanced lung cancer and recently underwent radiation therapy. Current vital signs demonstrate sinus tachycardia at $122\text{ /min}$, respiratory rate of $24\text{ /min}$, and a narrowed pulse pressure with a blood pressure of $88/72\text{ mm Hg}$. The extremities are cool to the touch, and the lungs are clear to auscultation bilaterally. Given the high suspicion for a rapidly progressive hemodynamic complication characterized by the accumulation of fluid in the pericardial space, which of the following physical examination findings would most accurately support this specific diagnosis? (Select 3 findings)

A 68-year-old man is evaluated in the pulmonology clinic for an 8-month history of progressive shortness of breath and a persistent dry cough. Physical examination reveals digital clubbing and fine, "Velcro-like" end-inspiratory crackles at both lung bases. Pulmonary function testing reveals a restrictive pattern with a markedly reduced diffusing capacity for carbon monoxide (DLCO).

High-resolution computed tomography (HRCT) of the chest demonstrates lower-lobe predominant subpleural reticular opacities and honeycombing. Bilateral calcified diaphragmatic pleural plaques are noted, along with focal areas of high-attenuation consolidation in the peripheral lung fields.

His past medical history is significant for hypertension, hyperlipidemia, and paroxysmal atrial fibrillation. His current medications include lisinopril, apixaban, atorvastatin, and amiodarone, which was initiated 3 years ago for rhythm control.

Social and occupational history reveals he worked as a commercial plumber and pipefitter for 35 years before retiring. He smoked 1 pack of cigarettes daily for 30 years but quit 15 years ago. He has kept two pet parrots in his living room for the past 10 years.

Based on the clinical and radiologic findings, which of the following elements from the patient's medical and social history are the most likely primary etiologies for his underlying pulmonary pathology? (Select 2)

A 24-year-old man presents to the emergency department with severe, bilateral thigh and shoulder pain, along with dark-colored urine. He reports that he participated in his first high-intensity interval training session earlier today. His temperature is 37.1°C (98.8°F), blood pressure is 120/80 mmHg, and pulse is 95/min. Physical examination shows diffusely tender and mildly swollen quadriceps and deltoid muscles. Which of the following is the most appropriate next step in laboratory evaluation?

A 65-year-old man with a history of a mechanical aortic valve replacement is hospitalized for a 2-week history of low-grade fever, fatigue, and night sweats. Physical examination reveals a new diastolic murmur and splinter hemorrhages on his fingernails. Multiple sets of blood cultures grow Enterococcus faecalis. Antimicrobial susceptibility testing indicates that the isolate is susceptible to ampicillin but exhibits high-level resistance to gentamicin (minimum inhibitory concentration > 500 µg/mL). The infectious disease team determines that the standard ampicillin and gentamicin synergistic combination will not be effective. Which of the following is the most likely molecular mechanism underlying this pathogen's resistance to the aminoglycoside?

For each patient presenting with a distinct hemorrhagic or thrombotic disorder, select the primary underlying pathophysiologic mechanism.

A 54-year-old woman is admitted to the intensive care unit for a severe exacerbation of chronic obstructive pulmonary disease. She is started on a continuous intravenous infusion of theophylline. After 48 hours, her plasma theophylline concentration reaches a steady state of $8 \text{ mg/L}$. To aggressively optimize bronchodilation, the intensivist triples the infusion rate. Simultaneous with this rate increase, the patient is diagnosed with a suspected multidrug-resistant infection, and rifampin, a potent cytochrome P450 inducer, is added to her regimen. Pharmacokinetic analysis indicates that rifampin therapy will precisely double the hepatic clearance of theophylline without altering its volume of distribution.

If the new, tripled theophylline infusion rate is maintained, which of the following accurately describes the patient's new theophylline steady-state concentration and the time required to reach it (compared to the original time to reach steady state)?

A 48-year-old man with severe, refractory rheumatoid arthritis is treated with an intravenous infusion of a chimeric monoclonal antibody. Twelve days after the infusion, he presents to the urgent care clinic with a new-onset pruritic rash, spiking fevers, and severe joint pain in his knees and wrists. Laboratory testing shows reduced serum C3 and C4 levels, an elevated erythrocyte sedimentation rate, and new-onset proteinuria. Arrange the following immunopathologic events in the correct chronological sequence that led to this patient's current clinical presentation.

A 68-year-old man with a history of hypertension, type 2 diabetes mellitus, and hyperlipidemia presents to the emergency department with a 4-hour history of severe, continuous vertigo, nausea, and an unsteady gait. The symptoms began abruptly while he was sitting and reading. He reports that any head movement severely exacerbates the nausea. He denies tinnitus, hearing loss, headache, or other focal neurologic symptoms. Vital signs are within normal limits. On physical examination, the patient appears distressed, prefers to keep his eyes closed, and has spontaneous nystagmus present in the primary position. The physician performs a targeted physical examination to differentiate between a central etiology (e.g., posterior circulation stroke) and a peripheral etiology (e.g., vestibular neuritis) for his acute vestibular syndrome.

Which of the following physical examination findings most strongly suggests a central etiology requiring urgent neuroimaging?

A 24-year-old woman comes to the clinic for evaluation of a lifelong history of heavy menstrual bleeding and frequent epistaxis that often takes more than 15 minutes to stop. She recently underwent a tooth extraction that was complicated by excessive bleeding requiring surgical packing. She takes no medications and has no other medical conditions. Her family history is notable for her mother having a 'bleeding problem' and undergoing a hysterectomy at age 35 for severe menorrhagia. Physical examination reveals a few scattered ecchymoses on her upper and lower extremities. A complete blood count shows a hemoglobin of 11.2 g/dL and a platelet count of 250,000/mm³. Coagulation studies demonstrate a normal prothrombin time (PT) and a mildly prolonged activated partial thromboplastin time (aPTT) of 42 seconds (reference: 25-35 seconds). Which of the following is the most appropriate next step in laboratory evaluation?

A 42-year-old man comes to the clinic for follow-up of poorly controlled hypertension. He is currently taking maximum doses of amlodipine and doxazosin. He occasionally experiences muscle weakness and cramps. His blood pressure is 164/100 mm Hg. Physical examination is otherwise unremarkable.

Laboratory studies show:

Based on the interpretation of these laboratory results, which of the following hormone profiles is most likely in this patient?

A 24-year-old professional skier is evaluated in the emergency department following a high-speed collision. Radiographs reveal a closed, comminuted fracture of the left tibial shaft. The leg is immobilized in a posterior splint, and he is admitted for planned open reduction and internal fixation the following morning. Three hours after admission, the patient complains of agonizing left leg pain that is no longer relieved by his prescribed intravenous hydromorphone. He describes the pain as a deep, unrelenting ache that feels significantly worse than the pain immediately following the initial injury. Vital signs are stable. Which of the following physical examination findings is the earliest and most reliable indicator for establishing the diagnosis of the suspected complication?

A 42-year-old agricultural worker is evaluated in the emergency department for progressive jaw stiffness, difficulty swallowing, and painful muscle spasms. Two weeks ago, he sustained a deep puncture wound to his left foot from a rusty nail while working in the field and did not seek medical care. Physical examination reveals marked trismus and spasms of the facial muscles, producing a fixed smile. The physician suspects an infection by a spore-forming, Gram-positive, obligate anaerobic bacillus. Arrange the following steps in the pathophysiologic cascade of this disease process in chronological order, from initial toxin entry to the final molecular mechanism causing the patient's symptoms.

A 24-year-old man is brought to the emergency department by his supervisor due to the acute onset of severe nausea, recurrent vomiting, dizziness, and profound weakness. The symptoms began 2 hours ago while he was at work. He is employed as a seasonal agricultural worker and has been manually harvesting tobacco leaves for the past three days. It rained heavily this morning, and the patient reports his clothes have been completely soaked; he was not wearing protective gloves.

Past medical history is unremarkable. Surgical history includes an uncomplicated appendectomy at age 12. Social history reveals he drinks alcohol occasionally but does not smoke or use illicit drugs. He takes no daily medications or supplements.

Physical examination reveals a temperature of 37.1°C (98.8°F), blood pressure of 155/95 mmHg, heart rate of 110/min, and respiratory rate of 18/min. The patient is pale and profusely diaphoretic. Neurologic examination shows a fine resting tremor in the hands but no muscle fasciculations. Pupils are 5 mm in diameter and bilaterally reactive to light. Cardiopulmonary examination reveals clear lungs with no wheezing or rhonchi. Bowel sounds are hyperactive. There is no excessive salivation, lacrimation, or bronchorrhea.

Based on the patient's medical and occupational history, which of the following is the most likely diagnosis?

A 19-year-old woman with a history of type 1 diabetes mellitus is brought to the emergency department by her roommate due to severe nausea, vomiting, and confusion for the past 24 hours. She has recently been suffering from a gastrointestinal viral illness and has not been taking her insulin because she was not eating. On physical examination, her mucous membranes are dry, and she is breathing rapidly and deeply.

Laboratory testing shows the following:

Based on these laboratory results, what is the patient's serum anion gap?

Match each patient's complex clinical presentation with the most appropriate targeted laboratory testing panel or specific initial diagnostic test to order to establish the diagnosis.

Match each patient's clinical presentation with the most appropriate targeted laboratory testing panel to establish the underlying diagnosis.

A 19-year-old man is brought to the emergency department by his roommate because of profound, progressive muscle weakness. The roommate reports that the patient has a history of recreational substance use but does not know what he recently used. On physical examination, the patient is awake but unable to lift his arms or legs against gravity. Deep tendon reflexes are absent. Vital signs are within normal limits.

Laboratory studies show:
Serum sodium: $137 \text{ mEq/L}$
Serum potassium: $1.8 \text{ mEq/L}$
Serum chloride: $114 \text{ mEq/L}$
Serum bicarbonate: $11 \text{ mEq/L}$
Blood urea nitrogen: $14 \text{ mg/dL}$
Serum creatinine: $0.9 \text{ mg/dL}$
Serum glucose: $95 \text{ mg/dL}$

Arterial blood gas (room air):
pH: $7.23$
pCO $_2$: $26 \text{ mm Hg}$
pO $_2$: $98 \text{ mm Hg}$

Urine studies:
pH: $6.5$
Sodium: $50 \text{ mEq/L}$
Potassium: $30 \text{ mEq/L}$
Chloride: $45 \text{ mEq/L}$

Which of the following is the most appropriate next step in laboratory evaluation to clarify the etiology of this patient's acid-base disturbance?

A $65$-year-old man is hospitalized for treatment of methicillin-resistant *Staphylococcus aureus* (MRSA) osteomyelitis. For the past week, he has been receiving a continuous intravenous infusion of a novel antimicrobial agent at a rate of $40$ mg/hr. His renal and hepatic functions have remained stable. Routine therapeutic drug monitoring reveals a steady-state plasma concentration of $8$ mg/L.

The patient is now clinically stable and is being prepared for discharge to complete a prolonged course of therapy. The infectious disease specialist recommends transitioning the patient to an oral formulation of the same medication. To ensure adequate bone penetration for the remainder of the therapy, the specialist also recommends targeting a higher average steady-state plasma concentration of $12$ mg/L.

The oral formulation of this medication has a known bioavailability of $60\%$ ($F = 0.60$). The planned dosing interval for the oral regimen is every $8$ hours.

Assuming the patient's pharmacokinetic parameters remain constant, what oral dose (in mg) should be administered every $8$ hours to achieve the new target concentration?