Internal Medicine

3151 questions

All types3,151 Multiple choice1,611 Multiple select73 Numeric81 Matching714 Ordering672

A 71-year-old man comes to the clinic due to the sudden onset of extensive bruising over his trunk and arms over the past two weeks. He also reports painful swelling in his right knee that began yesterday after bumping it against a table. He has a history of hypertension and osteoarthritis. He has never had abnormal bleeding before, including during a cholecystectomy 10 years ago. Current medications include lisinopril and acetaminophen. Vital signs are within normal limits. Physical examination reveals large, coalescing ecchymoses over the abdomen and proximal extremities. The right knee is warm, swollen, and tender. Laboratory studies show:

Test	Result	Reference Range
Hemoglobin	10.8 g/dL	13.5-17.5 g/dL
Platelet count	210,000/mm³	150,000-400,000/mm³
Prothrombin time (PT)	11.2 sec	11-15 sec
Activated partial thromboplastin time (aPTT)	78 sec	25-40 sec

A 1:1 mixing study with normal plasma is performed, and the aPTT remains prolonged at 72 seconds. Which of the following is the most appropriate next step in the management of this patient's bleeding?

Administer recombinant factor VIIa

Administer factor VIII concentrate

Administer desmopressin (DDAVP)

Transfuse fresh frozen plasma

Administer vitamin K

Show answer & explanation

Answer: Administer recombinant factor VIIa

Answer

Administer recombinant factor VIIa

The correct answer is to administer a bypassing agent such as recombinant factor VIIa. This patient's presentation of spontaneous deep tissue bleeding (hemarthrosis, large coalescing ecchymoses) in the seventh decade of life with no prior personal or family bleeding history is highly suggestive of an acquired bleeding disorder. The laboratory findings show an isolated prolonged activated partial thromboplastin time (aPTT). The critical diagnostic step is the 1:1 mixing study, which fails to correct the aPTT into the normal range. A failure to correct indicates the presence of an inhibitor (an autoantibody) rather than a simple factor deficiency. The most common acquired coagulation inhibitor is directed against factor VIII, leading to acquired hemophilia A. In the setting of acute, severe bleeding in acquired hemophilia A, providing standard factor VIII concentrate is ineffective because the circulating autoantibodies will rapidly neutralize it. Instead, hemostasis must be achieved using bypassing agents, specifically recombinant factor VIIa (rFVIIa) or activated prothrombin complex concentrate (aPCC). These agents bypass the intrinsic pathway defect by directly activating factor X or providing activated downstream factors, thereby enabling thrombin generation and subsequent clot formation.

Step-by-Step Solution

Analyze the basic coagulation profile.

The patient has an isolated prolonged aPTT with a normal PT and platelet count.

This localizes the hemostatic defect to the intrinsic coagulation pathway (factors VIII, IX, XI, or XII).

Interpret the mixing study results.

The aPTT fails to correct after mixing the patient's plasma 1:1 with normal plasma.

Failure to correct indicates the presence of a circulating coagulation inhibitor (an autoantibody), rather than a simple factor deficiency.

Synthesize the clinical presentation with the laboratory findings.

An elderly patient with no prior bleeding history presenting with sudden severe tissue bleeding and an inhibitor to the intrinsic pathway.

This is the classic presentation of acquired hemophilia A, which is caused by autoantibodies directed against factor VIII.

Determine the optimal acute management for the bleeding episode.

Bypass the inhibited factor VIII using specific bypassing agents.

Standard factor VIII replacement will be neutralized by the autoantibodies. Recombinant factor VIIa directly activates factor X, bypassing the need for factor VIII and allowing the coagulation cascade to proceed.

Key Concept

Acquired hemophilia A typically presents in older adults with acute, severe bleeding, an isolated prolonged aPTT, and failure of the aPTT to correct on a mixing study. Acute bleeding must be managed with bypassing agents such as recombinant factor VIIa or activated prothrombin complex concentrate.

Question 1262Question →

Secondary hypertension should be suspected in patients presenting with resistant hypertension, severe blood pressure elevations, or specific clinical manifestations. Match each patient vignette with the most appropriate initial diagnostic screening test to evaluate the underlying etiology.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Pheochromocytoma screens with metanephrines, primary hyperaldosteronism with the aldosterone-to-renin ratio, renal artery stenosis with duplex ultrasonography, and Cushing syndrome with the dexamethasone suppression test.

Secondary hypertension requires targeted testing based on clinical suspicion to avoid unnecessary and expensive diagnostic evaluations. The pairings correctly align each classic clinical presentation with its respective gold-standard initial screening modality as recommended by current clinical guidelines.

Step-by-Step Solution

Analyze the first vignette to identify the classic triad of pheochromocytoma.

Recognized symptoms of headache, tachycardia, and diaphoresis.

Matching these symptoms points directly to catecholamine excess, prompting the selection of plasma free metanephrines.

Evaluate the second vignette focusing on the electrolyte abnormality.

Identified spontaneous hypokalemia in a hypertensive patient.

This combination is highly suspicious for primary hyperaldosteronism, evaluated initially by checking the aldosterone-to-renin ratio.

Assess the third vignette for cardiovascular complications.

Recognized flash pulmonary edema in the setting of acute-on-chronic hypertension and atherosclerosis.

These findings are hallmark signs of renal artery stenosis, which is non-invasively screened using renal artery Doppler ultrasonography.

Review the fourth vignette for physical stigmata of endocrine disease.

Identified signs of hypercortisolism (striae, adiposity, osteopenia).

These physical examination findings indicate Cushing syndrome, requiring screening with an overnight dexamethasone suppression test.

Key Concept

Screening modalities for secondary causes of hypertension based on specific clinical presentations.

Question 1263Question →

A 45-year-old woman presents to the clinic with a 3-month history of bilateral wrist and metacarpophalangeal joint pain, accompanied by 2 hours of morning stiffness. Physical examination reveals symmetric synovitis of the hands and wrists. Arrange the following clinical steps in the most appropriate chronological order for the diagnosis and longitudinal pharmacologic management of this patient, assuming she experiences inadequate treatment responses at each subsequent stage.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct chronological sequence is: 1) Diagnostic confirmation with serology and imaging, 2) Initiation of methotrexate with bridging glucocorticoids, 3) Addition of a TNF-alpha inhibitor, and 4) Switching to a non-TNF biologic agent.

The management of rheumatoid arthritis follows a strict algorithmic step-up approach. It begins with definitive diagnostic testing (serology and imaging) to establish a baseline. Pharmacotherapy then universally begins with a conventional synthetic DMARD, primarily methotrexate, often paired with short-term glucocorticoids for symptom bridging. If the treatment target is not met within 3 to 6 months, therapy is escalated by adding a biologic DMARD, typically a TNF-alpha inhibitor. If this initial biologic fails to control the disease, standard practice dictates switching to a biologic with an alternative mechanism of action (e.g., rituximab).

Step-by-Step Solution

Confirm the clinical diagnosis.

Obtaining anti-CCP, rheumatoid factor, and baseline radiographs solidifies the diagnosis of rheumatoid arthritis and assesses early structural damage.

Definitive diagnosis and baseline evaluations are required before committing a patient to long-term immunosuppressive regimens.

Initiate first-line disease-modifying pharmacotherapy.

Starting methotrexate provides established disease modification, while short-term glucocorticoids offer immediate symptom relief.

Methotrexate is the evidence-based, universal first-line conventional synthetic DMARD for rheumatoid arthritis.

Escalate therapy due to inadequate initial response.

Adding a biologic DMARD, typically a TNF-alpha inhibitor, aggressively targets specific inflammatory cytokines.

Therapy escalation is required when moderate to high disease activity persists despite 3 to 6 months of maximally tolerated methotrexate.

Address primary biologic failure.

Switching to an agent like rituximab (anti-CD20) or tocilizumab (IL-6 inhibitor) provides a new therapeutic pathway.

Patients who do not respond to TNF-alpha blockade often respond to biologics that target alternative immune cascades.

Key Concept

Step-up pharmacological management of rheumatoid arthritis

Question 1264Question →

A 28-year-old man comes to the clinic because of a 5-day history of right knee pain and swelling. He reports that the knee feels stiff and is difficult to bend. He also notes a gritty sensation in both eyes and mild burning upon urination for the past two days. One month ago, he had an episode of severe diarrhea with abdominal cramping that resolved without treatment after a week. His temperature is $37.2^\circ\text{C}$ ( $99.0^\circ\text{F}$ ), blood pressure is $122/78\text{ mm Hg}$ , and pulse is $84/\text{min}$ . Physical examination shows a swollen, warm, and tender right knee with a moderate effusion. Conjunctival injection is present bilaterally. Arthrocentesis of the right knee yields synovial fluid with a leukocyte count of $18,000/\text{mm}^3$ and no crystals. Gram stain of the fluid is negative. Which of the following is the most appropriate next step in the management of this patient's joint condition?

Prescribe oral diclofenac

Administer intravenous ceftriaxone and oral azithromycin

Prescribe oral ciprofloxacin

Order HLA-B27 testing

Measure serum uric acid level

Show answer & explanation

Answer: Prescribe oral diclofenac

Answer

Prescribe oral diclofenac

The correct action is to prescribe an NSAID. The patient's history of preceding diarrhea followed by the triad of arthritis, conjunctivitis, and urethritis strongly indicates reactive arthritis. Because this is a sterile, immune-mediated inflammatory process, the first-line treatment for the symptomatic relief of joint pain and swelling is an NSAID such as diclofenac, naproxen, or ibuprofen.

Step-by-Step Solution

Analyze the clinical presentation and recent medical history.

The patient presents with asymmetric oligoarthritis, conjunctivitis, and urethritis one month after a diarrheal illness.

Identifying the classic triad (arthritis, conjunctivitis, urethritis) and the preceding trigger is essential for diagnosing reactive arthritis.

Evaluate the synovial fluid analysis.

The fluid is inflammatory (leukocyte count

18,000/\text{mm}^3

) but sterile (negative Gram stain and no crystals).

This rules out septic arthritis (which typically has leukocytes >

50,000/\text{mm}^3

and positive cultures) and crystal arthropathies.

Determine the optimal initial treatment for the diagnosed condition.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are the correct choice.

NSAIDs are the standard first-line therapy for managing the inflammatory joint symptoms of reactive arthritis.

Key Concept

Reactive arthritis typically presents with a triad of asymmetric oligoarthritis, conjunctivitis, and urethritis following a gastrointestinal or genitourinary infection, and is managed initially with NSAIDs.

Question 1265Question →

Match each patient's clinical scenario regarding malaria prevention or treatment with the most appropriate targeted pharmacotherapy.

Click a left item, then click its matching right item

Show answer & explanation

Answer

The correct matches require pairing the pregnant traveler with Mefloquine, the P. vivax patient with Primaquine, the severe P. falciparum patient with Intravenous artesunate, and the uncomplicated P. falciparum patient with Artemether-lumefantrine.

Malaria management is highly specific to the clinical context. Mefloquine is the safe and recommended chemoprophylaxis for pregnant women traveling to chloroquine-resistant areas. Primaquine specifically targets the dormant liver hypnozoites of Plasmodium vivax to prevent relapse. Severe Plasmodium falciparum malaria (indicated by high parasitemia, confusion, and organ failure) requires emergent intravenous artesunate. Uncomplicated Plasmodium falciparum can be safely managed with oral artemisinin-based combination therapies, such as artemether-lumefantrine.

Step-by-Step Solution

Evaluate the clinical status and species of malaria for each patient.

Patients are categorized into: prophylaxis in pregnancy, P. vivax hypnozoite eradication, severe P. falciparum, and uncomplicated P. falciparum.

Malaria treatment and prophylaxis algorithms depend heavily on clinical severity, Plasmodium species, local resistance patterns, and patient-specific factors.

Determine the appropriate regimen for the pregnant traveler.

Mefloquine is selected.

Mefloquine is the only recommended chemoprophylaxis for chloroquine-resistant areas that is safe in all trimesters of pregnancy. Doxycycline is teratogenic, and atovaquone-proguanil lacks sufficient safety data.

Determine the appropriate regimen to eradicate P. vivax hypnozoites.

Primaquine is selected.

P. vivax and P. ovale have dormant liver stages (hypnozoites) that standard blood schizonticides do not kill. Primaquine (or tafenoquine) is required to prevent relapse, provided the patient has normal G6PD levels.

Determine the appropriate therapy for severe P. falciparum malaria.

Intravenous artesunate is selected.

Severe malaria (defined by parasitemia >5%, altered mental status, renal failure, or respiratory distress) requires emergent parenteral therapy with intravenous artesunate to rapidly clear the parasite burden.

Determine the appropriate therapy for uncomplicated P. falciparum malaria.

Artemether-lumefantrine is selected.

Uncomplicated falciparum malaria in a chloroquine-resistant region is best treated with an oral artemisinin-based combination therapy (ACT).

Key Concept

Pharmacotherapy for malaria depends on the severity of illness, Plasmodium species, local resistance patterns, and patient-specific contraindications such as pregnancy or G6PD deficiency.

Question 1266Question →

A 68-year-old woman is brought to the emergency department by her family due to a severe headache, fever, and confusion that started earlier today. On examination, her temperature is 39.2°C (102.6°F), blood pressure is 110/70 mm Hg, and heart rate is 115/min. She exhibits nuchal rigidity and a new-onset right-sided facial droop with right arm weakness. Arrange the following steps in the most appropriate chronological sequence for the immediate management of this patient.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence of steps is: 1) Obtain blood cultures, 2) Administer empiric intravenous antibiotics and dexamethasone, 3) Perform a non-contrast CT scan of the head, and 4) Perform a lumbar puncture.

The patient presents with classic signs of meningitis along with focal neurologic deficits (right-sided weakness) and altered mental status. These 'red flags' require a head CT prior to a lumbar puncture to rule out a mass lesion or significant cerebral edema that could lead to herniation during the procedure. However, treating bacterial meningitis is a race against time. Therefore, blood cultures must be drawn immediately, followed by the immediate administration of empiric antibiotics and dexamethasone. Once therapy is initiated, the patient can safely undergo a CT scan of the head. If the CT is clear of mass effect, a lumbar puncture should then be performed. Although antibiotics may sterilize the cerebrospinal fluid culture, other parameters (cell count, glucose, protein, PCR) will still provide critical diagnostic information.

Step-by-Step Solution

Recognize the clinical presentation of suspected bacterial meningitis with high-risk features.

The patient has symptoms of meningitis (fever, headache, nuchal rigidity) along with red flags for increased intracranial pressure: age over 60, altered mental status, and focal neurologic deficits (facial droop, arm weakness).

Identifying high-risk features is crucial as it alters the standard management pathway by necessitating neuroimaging prior to a lumbar puncture.

Determine the first step in management.

Obtain blood cultures.

Blood cultures should be obtained before administering antibiotics to optimize the chances of identifying the causative pathogen, provided it does not cause a substantial delay in treatment.

Determine the timing of empiric medical therapy.

Administer empiric intravenous antibiotics and dexamethasone.

Bacterial meningitis is a medical emergency. Antibiotics and dexamethasone must be given immediately after blood cultures are drawn and should never be delayed for a CT scan or lumbar puncture.

Decide on the sequence of diagnostic procedures (CT vs. LP).

Perform a non-contrast CT scan of the head, followed by a lumbar puncture.

Because the patient has high-risk features for increased intracranial pressure, a CT scan must be performed first to rule out a mass lesion. Performing an LP without prior imaging in this setting could precipitate fatal brain herniation.

Key Concept

In patients with suspected bacterial meningitis who have indications for a head CT (e.g., focal neurologic deficit, altered mental status, immunocompromised state, age over 60), blood cultures should be drawn and empiric antibiotics administered immediately, prior to obtaining the CT scan and performing a lumbar puncture.

Estimated Time:1m 0s

Question 1267Question →

During multidisciplinary rounds in the surgical intensive care unit, the team evaluates the antimicrobial regimen for a 54-year-old man. The patient underwent an exploratory laparotomy 8 days ago for a perforated viscus. On his fifth postoperative day, he developed a temperature of 38.9°C (102.0°F) and tachycardia. His right internal jugular central venous catheter, which had been placed preoperatively, was removed, and blood cultures were drawn from peripheral veins and the catheter before removal. Empiric therapy with intravenous vancomycin and cefepime was initiated. Today, the microbiology laboratory reports that two out of two blood culture sets are growing Staphylococcus aureus. The susceptibility panel indicates resistance to penicillin and ampicillin, but susceptibility to oxacillin, cefazolin, vancomycin, and daptomycin. The patient has no known drug allergies. His current temperature is 37.2°C (99.0°F), blood pressure is 128/82 mmHg, and pulse is 82/min. Which of the following is the most appropriate next step in the pharmacologic management of this patient?

Discontinue vancomycin and cefepime; start intravenous daptomycin

Discontinue cefepime; continue intravenous vancomycin

Discontinue vancomycin and cefepime; start intravenous cefazolin

Continue both intravenous vancomycin and cefepime

Discontinue vancomycin and cefepime; start oral linezolid

Show answer & explanation

Answer: Discontinue vancomycin and cefepime; start intravenous cefazolin

Answer

Discontinue the empiric broad-spectrum antibiotics and transition to intravenous cefazolin for targeted MSSA therapy.

The patient has Methicillin-Susceptible Staphylococcus aureus (MSSA) bacteremia, indicated by susceptibility to oxacillin. The cornerstone of antimicrobial stewardship is de-escalating empiric therapy to the narrowest spectrum, most effective agent once culture and susceptibility data are available. For MSSA bacteremia, intravenous anti-staphylococcal beta-lactams (such as cefazolin, nafcillin, or oxacillin) are the drugs of choice. Extensive clinical data demonstrate that beta-lactams are superior to vancomycin for clearing MSSA bacteremia, resulting in lower rates of clinical failure, relapse, and mortality. Therefore, discontinuing the empiric vancomycin and cefepime and initiating intravenous cefazolin is the most appropriate next step.

Step-by-Step Solution

Interpret the blood culture and susceptibility results.

The pathogen is oxacillin-susceptible Staphylococcus aureus (MSSA).

Oxacillin susceptibility defines the isolate as MSSA, which changes the preferred treatment algorithm.

Evaluate the current empiric antimicrobial regimen (vancomycin and cefepime).

The current regimen is too broad and vancomycin is suboptimal for MSSA.

Antimicrobial stewardship dictates de-escalating to the narrowest effective agent. Beta-lactams are superior to vancomycin for MSSA.

Select the optimal targeted therapy.

Intravenous cefazolin (or nafcillin/oxacillin) is selected.

Cefazolin provides potent, narrow-spectrum bactericidal activity against MSSA with an excellent safety profile, making it the standard of care.

Key Concept

In patients with Methicillin-Susceptible Staphylococcus aureus (MSSA) bacteremia, targeted therapy with an intravenous anti-staphylococcal beta-lactam (e.g., cefazolin, nafcillin) is superior to vancomycin, leading to improved clinical outcomes and reduced mortality.

Estimated Time:1m 0s

Question 1268Question →

During a hospital observation, an 82-year-old male with a history of moderate chronic obstructive pulmonary disease and diet-controlled hypertension is receiving a blood transfusion. He was admitted earlier today for severe fatigue and was found to have a hemoglobin level of $6.2 \text{ g/dL}$ due to suspected chronic gastrointestinal blood loss. While receiving his second unit of packed red blood cells, he suddenly develops worsening shortness of breath and a dry cough. His blood pressure is $168/94 \text{ mmHg}$ , pulse is $112/\text{min}$ , and respiratory rate is $26/\text{min}$ . Oxygen saturation is $88\%$ on room air. Physical examination reveals distended neck veins and bilateral crackles at the lung bases. There is no fever, rash, or wheezing. Which of the following is the most appropriate next step in management?

Administer intravenous furosemide

Administer inhaled albuterol and ipratropium

Stop the transfusion and administer a bolus of intravenous normal saline

Transfer the patient to radiology for a computed tomography pulmonary angiogram

Initiate empiric treatment with intravenous vancomycin and cefepime

Show answer & explanation

Answer: Administer intravenous furosemide

Answer

Administer intravenous furosemide

The correct intervention is to administer intravenous furosemide. This patient is experiencing transfusion-associated circulatory overload (TACO), a known complication when blood products are administered rapidly or to patients vulnerable to volume expansion (such as the elderly). The classic presentation includes acute respiratory distress, hypertension, tachycardia, and physical exam findings of pulmonary edema (bibasilar crackles) and central volume overload (elevated jugular venous pressure). Management consists of immediately stopping the transfusion, providing supplemental oxygen, and aggressively diuresing the patient with an intravenous loop diuretic like furosemide.

Step-by-Step Solution

Analyze the patient's vital signs and physical examination findings during the transfusion.

The patient exhibits hypertension (

168/94 \text{ mmHg}

), tachycardia, hypoxia, distended neck veins, and bibasilar crackles without fever.

Identifying the hemodynamic status and presence of fluid overload is crucial to differentiate between various transfusion reactions.

Correlate the clinical findings with potential transfusion complications.

The combination of rapid blood product administration in an elderly patient leading to acute respiratory distress, hypertension, and signs of pulmonary edema (crackles, elevated jugular venous pressure) strongly indicates transfusion-associated circulatory overload (TACO).

Differentiating TACO from transfusion-related acute lung injury (TRALI) is key; TACO presents with hypertension and signs of volume overload, whereas TRALI typically presents with hypotension and no signs of left heart failure.

Determine the appropriate bedside intervention for TACO.

The correct management is to immediately stop the transfusion, provide respiratory support, and administer a diuretic (intravenous furosemide).

Diuresis rapidly decreases intravascular volume, reducing the hydrostatic pressure in the pulmonary capillaries and alleviating the pulmonary edema.

Key Concept

Recognition and management of transfusion-associated circulatory overload (TACO) using loop diuretics.

Question 1269Question →

During clinical rounds, the infectious disease service evaluates a 68-year-old male admitted with a two-week history of nocturnal sweats, generalized malaise, and a newly detected holosystolic murmur at the cardiac apex. Transesophageal echocardiography reveals a 1.4-cm mobile vegetation on the mitral valve along with moderate mitral regurgitation. The laboratory notifies the team that all four sets of blood cultures drawn upon admission are growing Enterococcus faecalis. The isolate demonstrates susceptibility to ampicillin, vancomycin, and daptomycin, but exhibits high-level resistance to gentamicin. Renal function is within normal limits. Which of the following is the most appropriate intravenous antibiotic regimen for this patient?

Ampicillin and ceftriaxone

Ampicillin and gentamicin

Ampicillin monotherapy

Daptomycin monotherapy

Linezolid monotherapy

Show answer & explanation

Answer: Ampicillin and ceftriaxone

Answer

The most appropriate regimen is the combination of ampicillin and ceftriaxone.

Enterococcal infective endocarditis strictly requires bactericidal therapy to eradicate the infection from avascular heart valve vegetations. Because ampicillin alone is only bacteriostatic against Enterococcus faecalis, it must be combined with a synergistic agent. Traditionally, an aminoglycoside (e.g., gentamicin) is used. However, this isolate has high-level aminoglycoside resistance (HLAR), meaning the synergistic bactericidal effect of gentamicin is lost. The combination of ampicillin and ceftriaxone provides excellent synergistic bactericidal activity against E. faecalis by saturating complementary penicillin-binding proteins (PBPs). Ampicillin primarily binds PBPs 4 and 5, while ceftriaxone binds PBPs 2 and 3. This dual beta-lactam regimen is the standard of care for HLAR isolates and is increasingly preferred even for aminoglycoside-susceptible isolates due to its equivalent efficacy and lower risk of nephrotoxicity.

Step-by-Step Solution

Identify the primary diagnosis and pathogen.

The patient has native valve infective endocarditis caused by Enterococcus faecalis.

Clinical presentation (fever, new murmur) combined with an echocardiographic vegetation and positive blood cultures confirm the diagnosis.

Determine the pharmacological requirements for treating this specific infection.

Enterococcal endocarditis requires bactericidal therapy to sterilize avascular heart vegetations.

Because cell-wall active agents (like ampicillin) are typically only bacteriostatic against enterococci, synergistic combination therapy is mandatory.

Analyze the susceptibility profile to select the correct synergistic combination.

The isolate exhibits high-level aminoglycoside resistance (HLAR), eliminating gentamicin as a viable synergistic agent.

HLAR means the aminoglycoside cannot effectively enter the bacterial cell even when the cell wall is compromised by ampicillin, resulting in a loss of synergistic bactericidal activity.

Select the alternative synergistic regimen.

Ampicillin combined with ceftriaxone is selected.

This double beta-lactam combination provides excellent synergistic bactericidal activity by saturating complementary penicillin-binding proteins, regardless of aminoglycoside susceptibility.

Key Concept

Treatment of Enterococcus faecalis infective endocarditis requires bactericidal synergy. In the presence of high-level aminoglycoside resistance (HLAR), dual beta-lactam therapy (ampicillin plus ceftriaxone) is the standard of care.

Question 1270Question →

An evaluation is requested for a $65$ -year-old man in the intensive care unit who developed right calf swelling and tenderness this morning. $6$ days ago, he underwent an exploratory laparotomy with a small bowel resection for acute mesenteric ischemia. His postoperative course has been complicated by severe acute kidney injury secondary to prolonged intraoperative hypotension, though he remains nonoliguric. Since admission, he has been receiving subcutaneous unfractionated heparin for deep venous thrombosis prophylaxis.

His temperature is $37.7^\circ\text{C}$ ( $99.9^\circ\text{F}$ ), blood pressure is $135/85$ mm Hg, pulse is $98$ /min, and respirations are $16$ /min. Physical examination reveals pitting edema and tenderness over the right calf. The laparotomy incision is clean, dry, and intact.

Laboratory results today:
Hemoglobin: $11.2$ g/dL
Platelet count: $85,000/\text{mm}^3$ (preoperative: $250,000/\text{mm}^3$ )
Leukocyte count: $9,500/\text{mm}^3$
Blood urea nitrogen: $48$ mg/dL
Serum creatinine: $3.4$ mg/dL

A compression ultrasonography of the right lower extremity confirms a new deep venous thrombosis in the popliteal vein. Which of the following is the most appropriate next step in the management of this patient?

Discontinue unfractionated heparin and initiate fondaparinux

Order a heparin-platelet factor 4 antibody assay and continue current therapy pending results

Discontinue unfractionated heparin and initiate warfarin

Discontinue unfractionated heparin and initiate an argatroban infusion

Obtain blood cultures and initiate empiric broad-spectrum antibiotics

Show answer & explanation

Answer: Discontinue unfractionated heparin and initiate an argatroban infusion

Answer

Discontinue unfractionated heparin and initiate an argatroban infusion

The correct answer involves immediately stopping all heparin products and starting an argatroban infusion. This patient developed a new deep venous thrombosis (DVT) and a

>50\%

drop in platelet count (from

250,000

85,000/\text{mm}^3

)

6

days after starting unfractionated heparin. This presentation is highly suspicious for Heparin-Induced Thrombocytopenia (HIT), a life-threatening prothrombotic state caused by IgG autoantibodies directed against the heparin-platelet factor 4 (PF4) complex. The '4Ts' score is high, indicating that immediate cessation of heparin and initiation of a non-heparin anticoagulant is mandatory. Because this patient has a significantly elevated serum creatinine (

3.4

mg/dL) indicating severe acute kidney injury, argatroban is the safest choice. Argatroban is a direct thrombin inhibitor that undergoes exclusively hepatic metabolism, avoiding toxic accumulation in renal failure.

Step-by-Step Solution

Calculate the 4Ts score to determine the clinical probability of Heparin-Induced Thrombocytopenia (HIT).

The score is high based on: Thrombocytopenia (drop > 50%), Timing (6 days), Thrombosis (new popliteal DVT), and absence of other clear causes.

A high 4Ts score necessitates immediate empiric intervention before laboratory confirmation is obtained.

Identify the immediate necessary intervention for suspected HIT.

All heparin products must be discontinued immediately, and a non-heparin anticoagulant must be started to prevent catastrophic thrombosis.

Continuing heparin or simply stopping it without starting an alternative agent leaves the patient at an unacceptably high risk for massive thrombosis.

Select the appropriate alternative anticoagulant based on patient comorbidities.

The patient has severe acute kidney injury (creatinine 3.4 mg/dL). Therefore, argatroban is selected over fondaparinux or bivalirudin.

Argatroban undergoes hepatic clearance and is safe in renal failure, whereas fondaparinux and bivalirudin are renally cleared and contraindicated in this setting.

Key Concept

Patients with highly probable Heparin-Induced Thrombocytopenia (HIT) require immediate cessation of all heparin and initiation of a non-heparin anticoagulant. In the setting of severe renal impairment, the direct thrombin inhibitor argatroban is the agent of choice due to its hepatic clearance.

Question 1271Question →

A 64-year-old man is brought to the emergency department due to a 2-day history of progressively worsening shortness of breath and coughing up blood-tinged sputum. His past medical history is significant for chronic rhinosinusitis that has been poorly responsive to multiple courses of antibiotics, and migrating joint pains for the past 6 months. His temperature is $37.6^\circ\text{C}$ ( $99.7^\circ\text{F}$ ), blood pressure is $155/95\text{ mmHg}$ , pulse is $108/\text{min}$ , and respiratory rate is $26/\text{min}$ . Oxygen saturation is 88% on room air. Physical examination reveals a mild collapse of the nasal bridge. Lung auscultation reveals diffuse bilateral crackles. Heart sounds are normal with no murmurs, gallops, or jugular venous distention. There is trace bilateral lower extremity edema. Laboratory results show:

Hemoglobin: $9.2\text{ g/dL}$
Leukocyte count: $14,000/\text{mm}^3$
Platelet count: $410,000/\text{mm}^3$
Blood urea nitrogen: $42\text{ mg/dL}$
Serum creatinine: $2.8\text{ mg/dL}$ (baseline $1.0\text{ mg/dL}$ 6 months ago)
Urinalysis: 2+ protein, large blood, 20-30 red blood cells/hpf, presence of red blood cell casts.

A portable chest radiograph shows bilateral, patchy, diffuse alveolar infiltrates. An electrocardiogram shows normal sinus rhythm. Which of the following is the most appropriate initial step in the management of this patient's acute condition?

Intravenous furosemide

Computed tomography angiography of the chest

High-dose intravenous methylprednisolone

Intravenous cyclophosphamide

Intravenous ceftriaxone and azithromycin

Show answer & explanation

Answer: High-dose intravenous methylprednisolone

Answer

The most appropriate initial step is the administration of high-dose intravenous methylprednisolone.

This patient's presentation is classic for Granulomatosis with Polyangiitis (GPA), a small-vessel ANCA-associated vasculitis. The clinical triad includes upper respiratory tract involvement (chronic sinusitis, saddle-nose deformity from cartilage destruction), lower respiratory tract involvement (diffuse alveolar hemorrhage manifesting as hemoptysis, dyspnea, hypoxia, and bilateral infiltrates), and renal involvement (rapidly progressive glomerulonephritis indicated by elevated creatinine and red blood cell casts). When GPA presents as a life-threatening pulmonary-renal syndrome, immediate and aggressive immunosuppression is mandatory. High-dose "pulse" intravenous corticosteroids (e.g., methylprednisolone) are the most critical initial step because they act rapidly to reduce acute inflammation and halt the alveolar hemorrhage. Other immunosuppressive agents, such as cyclophosphamide or rituximab, are subsequently added for remission induction, and plasmapheresis may be utilized in severe cases, but steroids are the most immediate life-saving intervention.

Step-by-Step Solution

Analyze the clinical presentation to identify the unifying diagnosis.

The combination of chronic sinusitis, saddle-nose deformity, diffuse alveolar hemorrhage, and rapidly progressive glomerulonephritis points to Granulomatosis with Polyangiitis (GPA).

GPA is a small-vessel ANCA-associated vasculitis characterized by this classic clinical triad affecting the upper respiratory tract, lower respiratory tract, and kidneys.

Determine the severity and primary threat of the patient's current presentation.

The patient has severe hypoxia, hemoptysis, and acute renal failure, indicating a life-threatening pulmonary-renal syndrome.

Diffuse alveolar hemorrhage is an acute emergency requiring immediate medical intervention to halt the autoimmune destruction and prevent respiratory failure.

Select the most appropriate initial management for this life-threatening vasculitis flare.

High-dose intravenous methylprednisolone is chosen.

Pulse-dose corticosteroids act rapidly to suppress the acute inflammatory cascade, whereas other induction agents (like cyclophosphamide) take too long to exert their full effect in an acute crisis.

Key Concept

Acute management of Granulomatosis with Polyangiitis (GPA) presenting with pulmonary-renal syndrome (diffuse alveolar hemorrhage and rapidly progressive glomerulonephritis).

Question 1272Question →

Match the following classic peripheral blood smear findings with their most likely associated hematologic disorder.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Spherocytes pair with Autoimmune hemolytic anemia; Bite cells pair with G6PD deficiency; Schistocytes pair with Thrombotic thrombocytopenic purpura; Auer rods pair with Acute myeloid leukemia; Smudge cells pair with Chronic lymphocytic leukemia.

Each peripheral smear finding represents a distinct pathophysiological process. Extravascular hemolysis via splenic membrane consumption yields spherocytes (AIHA). Oxidative RBC damage yields Heinz bodies and bite cells (G6PD deficiency). Intravascular mechanical shearing yields schistocytes (TTP). Myeloblast inclusions present as Auer rods (AML). Fragile neoplastic lymphocytes create smudge cells upon manual smearing (CLL).

Step-by-Step Solution

Identify the cause of spherocytes.

Matches with Autoimmune hemolytic anemia (AIHA).

Spherocytes result from membrane loss, classically seen in AIHA and hereditary spherocytosis.

Identify the condition presenting with bite cells and Heinz bodies.

Matches with Glucose-6-phosphate dehydrogenase (G6PD) deficiency.

Oxidative stress causes hemoglobin precipitation (Heinz bodies) which are 'bitten' out by splenic macrophages.

Identify the mechanism creating schistocytes.

Matches with Thrombotic thrombocytopenic purpura (TTP).

Schistocytes indicate microangiopathic hemolytic anemia, resulting from RBC shearing, typical of TTP.

Identify the lineage associated with Auer rods.

Matches with Acute myeloid leukemia (AML).

Auer rods are cytoplasmic inclusions specific to the myeloblast lineage seen in AML.

Identify the source of smudge cells.

Matches with Chronic lymphocytic leukemia (CLL).

CLL cells are unusually fragile and often burst during slide preparation, appearing as smudge cells.

Key Concept

Peripheral blood smear findings provide immediate diagnostic clues for differentiating various hematologic malignancies and hemolytic anemias based on their specific underlying pathophysiological mechanisms.

Estimated Time:1m 0s

Question 1273Question →

A $38$ -year-old woman is brought to the emergency department due to a $4$ -day history of worsening fatigue, spontaneous bruising, and continuous oozing of blood from her gums. Her temperature is $37.9^\circ\text{C}$ ( $100.2^\circ\text{F}$ ), blood pressure is $110/65 \text{ mm Hg}$ , and pulse is $112/\text{min}$ . Physical examination shows scattered petechiae and large ecchymoses over her extremities.

Laboratory studies reveal the following:

Laboratory Parameter	Patient Value	Reference Range
Hemoglobin	$7.8 \text{ g/dL}$	$12.0-15.5 \text{ g/dL}$
Platelets	$22,000/\text{mm}^3$	$150,000-400,000/\text{mm}^3$
Leukocytes	$1,800/\text{mm}^3$	$4,500-11,000/\text{mm}^3$
Prothrombin time (PT)	$19 \text{ sec}$	$11-15 \text{ sec}$
aPTT	$44 \text{ sec}$	$25-40 \text{ sec}$
Fibrinogen	$85 \text{ mg/dL}$	$200-400 \text{ mg/dL}$
D-dimer	$>10,000 \text{ ng/mL}$	$<500 \text{ ng/mL}$

A peripheral blood smear demonstrates pancytopenia and atypical promyelocytes with abundant primary granules and multiple rod-like intracytoplasmic inclusions bundled together.

Arrange the following steps in the most appropriate chronological order for the diagnosis and management of this patient's condition:

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence is to first initiate empiric ATRA, followed by confirmatory bone marrow testing, addition of ATO for definitive induction, management of potential differentiation syndrome with dexamethasone, and finally transition to maintenance therapy.

The correct sequence of management for acute promyelocytic leukemia (APL) prioritizes the immediate stabilization of life-threatening coagulopathy over definitive diagnostic confirmation. ATRA must be started empirically upon clinical suspicion (DIC plus characteristic faggot cells). This is followed sequentially by confirmatory bone marrow testing, definitive induction therapy with the addition of ATO, management of expected treatment complications like differentiation syndrome, and finally maintenance therapy to prevent relapse.

Step-by-Step Solution

Recognize the clinical presentation of Acute Promyelocytic Leukemia (APL).

The patient has pancytopenia, severe DIC (low fibrinogen, prolonged PT/aPTT, elevated D-dimer), and atypical promyelocytes with bundled Auer rods (faggot cells).

Identifying APL is critical because it is a medical emergency requiring a specific sequence of interventions.

Determine the first and most urgent therapeutic intervention.

Initiate ATRA immediately.

ATRA induces differentiation of leukemic cells, rapidly reversing the life-threatening coagulopathy. It must NOT be delayed for confirmatory testing.

Establish the definitive diagnosis.

Perform bone marrow aspiration and cytogenetic/molecular testing for

t(15;17)

or PML::RARA fusion.

Confirmatory testing is required to guide the full induction regimen, but is done after the initial emergency ATRA dose.

Plan the full induction chemotherapy regimen.

Add Arsenic Trioxide (ATO) or an anthracycline.

Once APL is confirmed, ATRA is combined with ATO to complete the induction phase and achieve remission.

Anticipate and manage induction complications.

Administer dexamethasone for differentiation syndrome.

As promyelocytes differentiate, they release cytokines causing fever, dyspnea, and pulmonary infiltrates (differentiation syndrome), which requires prompt steroid therapy.

Plan post-remission therapy.

Transition to maintenance therapy.

After induction and consolidation phases achieve molecular remission, maintenance therapy prevents relapse.

Key Concept

In patients with suspected acute promyelocytic leukemia (APL) presenting with disseminated intravascular coagulation, empiric all-trans retinoic acid (ATRA) must be initiated immediately prior to obtaining definitive molecular confirmation to prevent fatal hemorrhage.

Estimated Time:2m 0s

Question 1274Question →

Zoonotic and vector-borne infections can present with diverse, overlapping systemic symptoms. Their management heavily depends on the specific pathogen, disease stage, and patient comorbidities. Based on the clinical features provided, which antimicrobial regimen is the most appropriate next step in management for each patient? Match each clinical scenario with its optimal targeted pharmacotherapy.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Brucellosis matches with doxycycline and rifampin; Babesiosis matches with atovaquone and azithromycin; early localized Lyme disease in pregnancy matches with amoxicillin; Ehrlichiosis matches with doxycycline monotherapy; and severe Lyme carditis matches with intravenous ceftriaxone.

Each zoonotic and tick-borne illness requires a distinct, highly specific treatment based on pathogenesis and host factors. Brucellosis requires dual therapy (doxycycline and rifampin) for deep tissue clearance. Babesiosis, an intraerythrocytic protozoan, responds to atovaquone and azithromycin. While doxycycline is the standard for most tick-borne diseases (including Ehrlichiosis and non-pregnant Lyme disease), it is teratogenic; thus, early Lyme in pregnancy is treated with amoxicillin. Finally, severe Lyme carditis with syncope mandates intravenous ceftriaxone for adequate systemic and tissue penetration.

Step-by-Step Solution

Identify the underlying tick-borne or zoonotic pathogen for each clinical vignette.

Pathogens identified: Brucella spp., Babesia microti, Borrelia burgdorferi (early), Ehrlichia chaffeensis, and Borrelia burgdorferi (disseminated/cardiac).

Correct diagnosis is the prerequisite for targeted antimicrobial selection.

Evaluate patient-specific modifiers and disease severity in each scenario.

Modifiers identified: Occupational exposure for Brucella, asplenia for Babesia, pregnancy for early Lyme, classic blood smear for Ehrlichia, and third-degree AV block for disseminated Lyme.

Host factors (like pregnancy) and disease severity (like heart block) fundamentally alter the standard pharmacological approach.

Pair the diagnosed condition with current guideline-directed antimicrobial therapy.

The appropriate regimens are selected, actively avoiding teratogenic drugs in pregnancy and utilizing parenteral therapy for severe cardiac manifestations.

Ensures adherence to antibiotic stewardship and patient safety principles.

Key Concept

Diagnosis and targeted antimicrobial management of zoonotic and vector-borne infections, adapting treatment for disease severity and patient-specific contraindications.

Question 1275Question →

Autoantibodies serve as crucial diagnostic markers in evaluating systemic autoimmune conditions. Match each specific clinical manifestation profile with the autoantibody most characteristically associated with the underlying disease.

Click a left item, then click its matching right item

Show answer & explanation

Answer

The clinical profiles appropriately map to their highly specific serologic autoantibody markers based on presentation.

Each autoantibody has a distinct diagnostic sensitivity and specificity profile that aligns with specific clinical syndromes. Anti-Ro/SSA strongly correlates with Sjögren syndrome; anti-centromere indicates limited cutaneous systemic sclerosis; anti-histone is the hallmark of drug-induced lupus; and anti-U1 RNP is absolutely required for the diagnosis of mixed connective tissue disease.

Step-by-Step Solution

Analyze the first clinical profile describing xerostomia, parotid swelling, and keratoconjunctivitis sicca.

Identified as classic Sjögren syndrome.

This autoimmune exocrinopathy targets salivary and lacrimal glands, which strongly correlates with anti-Ro/SSA antibodies.

Evaluate the profile featuring distal skin thickening, vasospasm, and esophageal dysmotility.

Identified as limited cutaneous systemic sclerosis (CREST syndrome).

The symptoms represent Calcinosis, Raynaud phenomenon, Esophageal dysmotility, Sclerodactyly, and Telangiectasia, linked to anti-centromere antibodies.

Assess the clinical profile involving rash, arthritis, and pleuritis after taking procainamide.

Identified as drug-induced lupus erythematosus.

Procainamide is a classic high-risk medication for this condition, characterized by positive anti-histone antibodies.

Analyze the final profile involving overlapping features of multiple connective tissue diseases.

Identified as mixed connective tissue disease (MCTD).

MCTD requires the presence of clinical overlap features combined with positive anti-U1 RNP antibodies for diagnosis.

Key Concept

Serologic Autoantibody Associations in Rheumatologic Diseases

Question 1276Question →

Match each patient's clinical scenario with the most appropriate antimicrobial management strategy, reflecting current infectious disease and antimicrobial stewardship guidelines.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Asymptomatic bacteriuria in a catheterized patient pairs with observation without antimicrobial therapy; a cat bite puncture wound pairs with oral amoxicillin-clavulanate; primary syphilis with an anaphylactic penicillin allergy pairs with oral doxycycline; and a first episode of Clostridioides difficile colitis pairs with oral fidaxomicin.

Effective infectious disease management relies on identifying when to withhold therapy (asymptomatic bacteriuria) and when to prescribe targeted agents based on predictable microbiology (Pasteurella in cat bites), drug allergy constraints (doxycycline for syphilis in penicillin allergy), and updated primary guidelines (fidaxomicin for initial C. difficile).

Step-by-Step Solution

Evaluate each vignette to determine if antimicrobial therapy is clinically indicated based on stewardship guidelines.

The elderly patient with a catheter has asymptomatic bacteriuria, which does not require treatment. The other three patients have active infections or high-risk exposures requiring pharmacotherapy.

Avoiding antibiotics in colonized, asymptomatic patients is a fundamental principle of antimicrobial stewardship to prevent resistance and drug toxicity.

Select the most appropriate, guideline-concordant antimicrobial agent for the remaining active scenarios.

Amoxicillin-clavulanate covers Pasteurella in cat bites. Doxycycline is the safest alternative for syphilis in penicillin anaphylaxis. Fidaxomicin is first-line for C. difficile.

Proper stewardship requires matching the drug's spectrum of activity to the expected pathogen while accounting for patient-specific factors like severe allergies.

Key Concept

Guideline-directed antimicrobial selection and antibiotic stewardship

Question 1277Question →

A 42-year-old man presents to the emergency department with a 4-week history of a persistent productive cough, subjective low-grade fevers, drenching night sweats, and an unintentional 5-kg (11-lb) weight loss. He immigrated to the United States from Southeast Asia five years ago. His vital signs are temperature 38.1°C (100.6°F), blood pressure 118/76 mmHg, heart rate 92/min, and respiratory rate 18/min. A portable chest radiograph performed in the emergency department demonstrates a 3-cm cavitary lesion in the apical segment of the right upper lobe. The patient is currently resting in a standard emergency department examination room with the door closed.

Arrange the following interventions in the most appropriate chronological sequence for the comprehensive management of this patient.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct chronological sequence is to first isolate the patient in a negative-pressure room, followed by collecting diagnostic sputum samples, initiating empiric four-drug therapy, coordinating with public health for directly observed therapy prior to discharge, and finally narrowing the regimen to two drugs after two months.

The management of suspected active pulmonary tuberculosis requires a multidisciplinary, stepwise approach designed to protect the public while definitively treating the patient. The absolute first step upon suspecting active pulmonary tuberculosis (suggested by the classic presentation of an upper lobe cavitary lesion, weight loss, night sweats, and endemic geographic history) is to place the patient in an airborne infection isolation room. Delaying isolation exposes healthcare workers and other patients to aerosolized mycobacteria. Once isolated, diagnostic samples (acid-fast bacilli smears, cultures, and nucleic acid amplification) must be collected. It is a core principle of antibiotic stewardship to obtain these samples before antimicrobial administration to ensure high diagnostic yield and allow for accurate drug susceptibility testing. Immediately following sample collection, an empiric intensive-phase regimen of four drugs (rifampin, isoniazid, pyrazinamide, ethambutol) is initiated. Before the patient can be safely discharged back into the community, coordination with local public health authorities is mandatory to establish directly observed therapy (DOT), ensuring adherence and preventing multidrug-resistant strains. Finally, after two months of the four-drug intensive phase and confirmation of drug susceptibilities, the regimen is safely de-escalated to a two-drug continuation phase (typically isoniazid and rifampin).

Step-by-Step Solution

Transfer the patient to a negative-pressure airborne infection isolation room.

Nosocomial transmission risk is immediately mitigated.

Airborne precautions are the absolute first priority in any patient with clinical and radiographic features suspicious for active pulmonary tuberculosis.

Collect three sputum specimens spaced 8 to 24 hours apart.

Diagnostic material is secured for AFB smear, NAAT, and mycobacterial culture.

Microbiological confirmation and drug susceptibility testing require high-quality samples obtained prior to the administration of any antimicrobial therapy to prevent false-negative cultures.

Initiate an empiric antituberculous regimen with isoniazid, rifampin, pyrazinamide, and ethambutol.

The 2-month intensive phase of treatment begins.

Prompt initiation of four-drug empiric therapy is indicated for highly suspicious cavitary disease immediately after diagnostic samples are secured.

Coordinate with local public health authorities to arrange directly observed therapy (DOT).

A structured outpatient adherence plan is established.

Systems-based practice dictates establishing DOT before hospital discharge to ensure treatment compliance and minimize the risk of developing multidrug-resistant tuberculosis (MDR-TB) in the community.

Narrow the antimicrobial regimen to isoniazid and rifampin.

The patient transitions to the continuation phase of therapy.

The standard continuation phase begins only after the 2-month intensive phase is completed, clinical improvement is noted, and susceptibilities confirm the absence of drug resistance.

Key Concept

The management of suspected active pulmonary tuberculosis follows a strict chronological pathway prioritizing airborne infection isolation, securing diagnostic microbiologic samples, initiating empiric multi-drug therapy, and ensuring public health coordination via directly observed therapy.

Estimated Time:2m 0s

Question 1278Question →

For each of the following patients, select the most appropriate targeted antimicrobial therapy based on current clinical guidelines and stewardship principles.

Click a left item, then click its matching right item

Show answer & explanation

Answer

The non-pregnant patient with Lyme receives oral doxycycline. The pregnant patient with Lyme receives oral amoxicillin. The patient with isolated gonorrhea receives intramuscular ceftriaxone monotherapy. The patient with EBV and streptococcal pharyngitis receives oral penicillin V.

Each specific clinical scenario requires a nuanced selection of antibiotics. Non-pregnant patients with early Lyme disease receive doxycycline. Pregnant patients with early Lyme must avoid tetracyclines and receive amoxicillin instead. Uncomplicated, isolated gonococcal infection is now treated with ceftriaxone alone to promote antibiotic stewardship (sparing azithromycin). Finally, treating streptococcal pharyngitis in a patient with infectious mononucleosis requires penicillin V to avoid the characteristic aminopenicillin-induced rash.

Step-by-Step Solution

Identify the underlying infectious etiology for each clinical presentation.

Diagnoses identified: 1) Early Lyme disease. 2) Early Lyme disease in pregnancy. 3) Isolated gonococcal urethritis. 4) Streptococcal pharyngitis with concurrent Epstein-Barr virus.

Accurate diagnosis is required before selecting empiric or targeted therapy.

Apply patient-specific contraindications and current antimicrobial stewardship guidelines.

Avoid doxycycline in pregnancy, avoid amoxicillin in EBV, and avoid dual therapy for gonorrhea when chlamydia is negative.

Standard therapies often require adjustment based on age, pregnancy status, concurrent infections, and updated stewardship protocols.

Match each tailored regimen to the correct patient scenario.

Matches established correctly based on optimized safety and efficacy.

Ensures the patient receives the most appropriate, narrow-spectrum, and safe antimicrobial.

Key Concept

First-line antimicrobial selection and stewardship in common infectious diseases

Estimated Time:1m 0s

Question 1279Question →

A 67-year-old female presents to an outpatient clinic complaining of progressively worsening shortness of breath over the last three days. She has a medical history of essential hypertension, hyperlipidemia, and a 45-pack-year smoking history. She reports increased chest tightness and wheezing but notes her daily cough remains productive of only minimal, clear sputum. She denies any fever, chills, orthopnea, or paroxysmal nocturnal dyspnea. Her medications include amlodipine, atorvastatin, and an albuterol inhaler. The temperature is 37.0°C (98.6°F), blood pressure is 154/90 mm Hg, pulse is 95/min, and respiratory rate is 22/min. Pulse oximetry reveals an oxygen saturation of 91% on room air. The jugular venous pressure is estimated at 5 cm H2O. Chest auscultation reveals a prolonged expiratory phase with widespread, high-pitched polyphonic wheezing bilaterally. No crackles or cardiac murmurs are heard. There is trace, chronic non-pitting edema of the lower extremities. Which of the following is the most appropriate next step in management?

Administer intravenous furosemide

Prescribe oral azithromycin

Administer oral prednisone and nebulized ipratropium-albuterol

Obtain an arterial blood gas to calculate expected respiratory compensation

Order an urgent echocardiogram

Show answer & explanation

Answer: Administer oral prednisone and nebulized ipratropium-albuterol

Answer

Administer oral prednisone and nebulized ipratropium-albuterol

The correct answer involves treating the acute chronic obstructive pulmonary disease (COPD) exacerbation with systemic glucocorticoids and inhaled bronchodilators. The patient's presentation of progressive dyspnea, polyphonic wheezing, prolonged expiration, and a long smoking history strongly supports an acute exacerbation of COPD. Immediate management involves short-acting bronchodilators (such as albuterol and ipratropium) and systemic glucocorticoids (such as oral prednisone) to rapidly reduce airway inflammation and reverse bronchospasm. Antibiotics are correctly withheld because the patient's sputum remains clear, meaning she lacks the cardinal sign of increased sputum purulence required to justify antimicrobial therapy in this setting.

Step-by-Step Solution

Identify the primary clinical syndrome based on vital signs and physical examination.

The patient has progressive dyspnea, tachypnea, polyphonic wheezing, and a prolonged expiratory phase, which points to an acute exacerbation of chronic obstructive pulmonary disease (AECOPD).

Recognizing the hallmark signs of bronchospasm and airflow limitation is essential for directing initial therapy.

Differentiate between an AECOPD and acute decompensated heart failure.

The absence of elevated jugular venous pressure, pulmonary crackles, orthopnea, and paroxysmal nocturnal dyspnea makes heart failure highly unlikely.

Heart failure and COPD exacerbations can present with similar symptoms (dyspnea, wheezing) but require drastically different treatments.

Evaluate criteria for empiric antibiotic therapy in a COPD exacerbation.

The patient lacks increased sputum purulence or significant changes in sputum volume, so she does not meet the criteria for antibiotics.

Antibiotic stewardship principles dictate that antibiotics should only be given to AECOPD patients with specific cardinal symptoms indicating a likely bacterial infection.

Select the most appropriate initial pharmacologic therapy.

Systemic glucocorticoids (e.g., oral prednisone) and short-acting inhaled bronchodilators (e.g., ipratropium-albuterol) are chosen.

This combination rapidly reverses bronchospasm, decreases airway inflammation, and improves clinical outcomes in non-infectious COPD exacerbations.

Key Concept

Management of acute chronic obstructive pulmonary disease (COPD) exacerbations and avoiding inappropriate antibiotic use.

Estimated Time:1m 0s

Question 1280Question →

A 24-year-old female undergoes comprehensive coagulation testing for a lifelong history of mucocutaneous bleeding and menorrhagia. Her hematologist suspects a variant of von Willebrand disease (vWD) and orders a full diagnostic panel, including vWF antigen (vWF:Ag), vWF ristocetin cofactor activity (vWF:RCo), Factor VIII activity, ristocetin-induced platelet aggregation (RIPA), and multimer analysis. Match the specific laboratory profiles below with their exact underlying molecular pathophysiology.

Click a left item, then click its matching right item

Show answer & explanation

Answer

The laboratory profiles map to vWD subtypes as follows: enhanced RIPA/thrombocytopenia matches the gain-of-function glycoprotein Ib binding (Type 2B); isolated low Factor VIII matches impaired carrier binding (Type 2N); proportionate decrease matches partial quantitative deficiency (Type 1); and decreased RIPA matches ADAMTS13 susceptibility/assembly defect (Type 2A).

Precise classification of von Willebrand disease subtypes is critical because their management differs drastically. For example, administering desmopressin (DDAVP) is a standard treatment for Type 1, but it is contraindicated in Type 2B because it can exacerbate spontaneous platelet agglutination and worsen thrombocytopenia. The distinct laboratory findings provided in the stem directly reflect the underlying molecular pathophysiology for each subtype, allowing for definitive matching.

Step-by-Step Solution

Identify the quantitative variant (proportionate decrease, ratio > 0.7).

Matches the partial quantitative deficiency of functionally normal vWF (Type 1).

In Type 1 vWD, the defect affects the amount of vWF, not its structure or function, preserving the ratio.

Isolate the variant mimicking Hemophilia A (low Factor VIII, normal vWF parameters).

Matches the mutation impairing vWF's carrier binding affinity (Type 2N).

vWF acts as a protective carrier protein for Factor VIII. When this binding site is defective, Factor VIII is rapidly degraded in the plasma.

Distinguish between the two variants with absent large multimers (ratio < 0.7). Evaluate the profile with markedly decreased RIPA and a normal platelet count.

Matches the mutation rendering vWF susceptible to ADAMTS13 cleavage or impairing assembly (Type 2A).

Without large multimers, normal platelet agglutination fails, resulting in decreased RIPA.

Evaluate the remaining multimer-deficient profile showing enhanced RIPA at low-dose ristocetin and mild thrombocytopenia.

Matches the gain-of-function mutation causing excessive spontaneous binding to glycoprotein Ib (Type 2B).

The hyperactive vWF spontaneously binds platelets in vivo, clearing large multimers and platelets from circulation, which explains both the enhanced in vitro aggregation to minimal ristocetin and the in vivo thrombocytopenia.

Key Concept

Pathophysiology and advanced laboratory differentiation of von Willebrand Disease (vWD) subtypes

Alternative Method

When evaluating vWD panels, always look at the vWF:RCo to vWF:Ag ratio first. If > 0.7, it is a quantitative defect (Type 1 or 3). If < 0.7, it is a qualitative defect (Type 2A, 2B, or 2M). From there, use RIPA and multimer analysis to differentiate the Type 2 variants.

Estimated Time:3m 0s

PreviousPage 64 / 158Next

Internal Medicine

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept