Internal Medicine Practice Questions — USMLE Step 2 CK — Page 59

Question 1161Question →

Match the following clinical presentations of patients with advanced HIV infection to the most appropriate initial targeted antimicrobial therapy.

Click a left item, then click its matching right item

Show answer & explanation

Answer

The correct matches are: 1) CMV retinitis matched to Valganciclovir, 2) Cryptococcal meningoencephalitis matched to Liposomal amphotericin B and flucytosine, 3) Pneumocystis jirovecii pneumonia matched to Trimethoprim-sulfamethoxazole, and 4) Toxoplasma encephalitis matched to Sulfadiazine, pyrimethamine, and leucovorin.

Each clinical vignette describes classic pathognomonic findings for specific HIV-related opportunistic infections. CMV retinitis presents with retinal hemorrhages and exudates and is treated with valganciclovir. Cryptococcal meningitis presents with elevated intracranial pressure and positive capsular antigen, requiring induction therapy with liposomal amphotericin B and flucytosine. PJP presents with bilateral ground-glass opacities and is treated with high-dose TMP-SMX. Toxoplasma encephalitis presents with ring-enhancing lesions and seizures, necessitating treatment with sulfadiazine, pyrimethamine, and leucovorin (to prevent pyrimethamine-induced hematologic toxicity).

Step-by-Step Solution

1

Identify the underlying opportunistic infection based on the clinical vignette findings and the patient's CD4 cell count threshold.

Diagnoses identified are CMV retinitis, Cryptococcal meningoencephalitis, Pneumocystis jirovecii pneumonia (PJP), and Toxoplasma gondii encephalitis.

Accurate pathogen identification is required to select the precise targeted antimicrobial therapy.

2

Select the appropriate first-line antimicrobial regimen for each definitively identified pathogen.

Matched each opportunistic infection to its respective gold-standard pharmacotherapy.

Using the correct targeted therapy maximizes clinical efficacy and adheres to established infectious disease guidelines.

Key Concept

Diagnosis and first-line targeted therapy of major opportunistic infections in patients with advanced HIV based on CD4 count thresholds and classic clinical presentations.

Question 1162Question →

A 34-year-old woman is hospitalized for a 3-week history of daily fevers up to 39.8°C (103.6°F), severe polyarthralgia, and a faint, salmon-colored macular rash on her trunk that appears predominantly during febrile episodes. Physical examination reveals cervical lymphadenopathy and mild hepatosplenomegaly. Initial laboratory studies show:

Hemoglobin: 10.2 g/dL
Leukocytes: 18,500/mm³ (85% neutrophils)
Platelets: 450,000/mm³
Erythrocyte sedimentation rate (ESR): 95 mm/h
Ferritin: 8,500 ng/mL

Antinuclear antibody and rheumatoid factor testing are negative. She is started on empiric NSAIDs and corticosteroids for suspected adult-onset Still's disease. Three days later, her condition acutely deteriorates. She becomes lethargic and her temperature remains elevated at 40.1°C (104.2°F). Repeat laboratory studies show:

Hemoglobin: 8.1 g/dL
Leukocytes: 3,200/mm³
Platelets: 45,000/mm³
Erythrocyte sedimentation rate (ESR): 12 mm/h
Aspartate aminotransferase (AST): 450 U/L
Alanine aminotransferase (ALT): 520 U/L
Triglycerides: 480 mg/dL

Which of the following best explains the marked decrease in this patient's erythrocyte sedimentation rate compared to admission?

Profound depletion of circulating fibrinogen

Inhibition of hepatic acute-phase reactant synthesis by corticosteroids

Massive consumption of coagulation factors driven by occult bacterial sepsis

Decreased concentration of erythrocytes due to acute myelosuppression

Alteration of erythrocyte surface charge by bound autoantibodies

Show answer & explanation

Answer: Profound depletion of circulating fibrinogen

Answer

The correct answer is profound depletion of circulating fibrinogen.

The correct answer correctly identifies that a profound depletion of circulating fibrinogen is responsible for the rapidly falling ESR. The patient's acute deterioration is classic for Macrophage Activation Syndrome (MAS), a form of secondary hemophagocytic lymphohistiocytosis (HLH) that frequently complicates adult-onset Still's disease. The excessive macrophage activation in MAS leads to a massive cytokine storm and a consumptive coagulopathy characterized by severe hypofibrinogenemia. Because the ESR is highly dependent on fibrinogen to neutralize the negative charge of red blood cells and facilitate rouleaux formation, the acute loss of fibrinogen causes a paradoxical plummet in the ESR, even while the patient's systemic inflammation is peaking.

Step-by-Step Solution

1

Analyze the patient's initial clinical presentation and laboratory findings.

The combination of quotidian fevers, salmon-colored rash, polyarthritis, seronegativity, extreme hyperferritinemia, and elevated ESR supports a diagnosis of adult-onset Still's disease (AOSD).

Establishing the underlying diagnosis provides the context for recognizing specific, disease-associated complications.

2

Evaluate the clinical deterioration three days after admission.

The acute onset of lethargy, persistent high fever, pancytopenia, elevated transaminases, and hypertriglyceridemia strongly indicate the development of Macrophage Activation Syndrome (MAS).

MAS is a form of secondary hemophagocytic lymphohistiocytosis (HLH) and is a life-threatening complication of rheumatologic conditions, most notably systemic juvenile idiopathic arthritis and AOSD.

3

Determine the pathophysiological mechanism behind the paradoxical drop in ESR.

In MAS, massive macrophage activation causes a severe cytokine storm and consumptive coagulopathy, leading to a marked decrease in circulating fibrinogen (hypofibrinogenemia).

The erythrocyte sedimentation rate (ESR) is directly dependent on asymmetric macromolecules, primarily fibrinogen, which coat red blood cells and promote rouleaux formation. When fibrinogen is rapidly consumed in MAS, the ESR precipitously drops to near-normal or low levels despite overwhelming systemic inflammation.

Key Concept

Macrophage activation syndrome (MAS) is a severe complication of adult-onset Still's disease characterized by pancytopenia, hypertriglyceridemia, transaminitis, and hyperferritinemia. Consumptive hypofibrinogenemia classically results in a paradoxical, sharp decrease in the erythrocyte sedimentation rate despite worsening systemic inflammation.

Question 1163Question →

A $68$ -year-old man is evaluated on postoperative day $6$ following an elective right total hip arthroplasty. He reports new-onset right calf pain and swelling that began this morning. His temperature is $38.1^\circ\text{C}$ ( $100.6^\circ\text{F}$ ), blood pressure is $130/80$ mmHg, pulse is $98$ /min, and respirations are $16$ /min. Physical examination reveals a swollen, tender right calf with mild erythema. Since admission, the patient has been receiving subcutaneous enoxaparin for deep vein thrombosis prophylaxis. Laboratory studies show:

Indicator	Value
Hemoglobin	$12.4$ g/dL
Platelet count	$105,000/\mu\text{L}$ (Baseline on admission: $260,000/\mu\text{L}$ )
Leukocyte count	$9,500/\mu\text{L}$
Serum creatinine	$1.1$ mg/dL

A venous Doppler ultrasound of the right lower extremity confirms an acute deep venous thrombosis in the popliteal vein. Which of the following is the most appropriate next step in management?

Discontinue enoxaparin and initiate argatroban

Discontinue enoxaparin and initiate unfractionated heparin

Continue enoxaparin and initiate warfarin

Continue enoxaparin and administer broad-spectrum antibiotics

Discontinue enoxaparin and administer a platelet transfusion

Show answer & explanation

Answer: Discontinue enoxaparin and initiate argatroban

Answer

Discontinue enoxaparin and initiate argatroban

The correct approach involves immediately stopping all heparin products and starting a non-heparin anticoagulant, such as the direct thrombin inhibitor argatroban. This patient has classic features of Heparin-Induced Thrombocytopenia (HIT) Type 2: a

>50\%

drop in platelet count occurring

5

to

10

days after the initiation of a heparin product (enoxaparin), accompanied by a new thrombotic event (DVT). HIT is an immune-mediated disorder caused by IgG antibodies against the heparin-platelet factor 4 (PF4) complex, which activates platelets and triggers widespread thrombosis. Because enoxaparin is the inciting agent, it must be discontinued. However, the patient remains at a very high risk for further life-threatening thromboses, so a non-heparin alternative must be started promptly.

Step-by-Step Solution

1

Analyze the clinical presentation and timing.

Postoperative day 6 patient with a new deep vein thrombosis (DVT) and low-grade fever.

To establish the acute clinical problem requiring management.

2

Evaluate the laboratory findings in context.

Platelet count dropped from

260,000/\mu\text{L}

to

105,000/\mu\text{L}

(a

>50\%

decrease) while on enoxaparin.

To identify potential complications of pharmacological prophylaxis.

3

Synthesize findings to formulate a diagnosis.

The timing (5-10 days post-exposure),

>50\%

platelet drop, and new thrombosis are highly suggestive of Heparin-Induced Thrombocytopenia (HIT) Type 2.

To determine the underlying pathophysiology of the new DVT.

4

Determine the appropriate management for the diagnosis.

All heparin products (including LMWH) must be stopped immediately, and a non-heparin anticoagulant like a direct thrombin inhibitor (e.g., argatroban) must be started.

To prevent further immune-mediated platelet activation and thrombosis.

Key Concept

Diagnosis and management of Heparin-Induced Thrombocytopenia (HIT) Type 2

Estimated Time:1m 30s

Question 1164Question →

An infectious diseases consultation is requested for a $59$ -year-old male inpatient. He was admitted $4$ days ago with severe back pain and fever, leading to a diagnosis of $\text{T10}-\text{T11}$ vertebral osteomyelitis and an associated epidural abscess. Urgent surgical decompression and debridement were performed on the day of admission. Blood cultures obtained prior to antibiotic administration, as well as intraoperative tissue specimens, have both grown Staphylococcus aureus. Susceptibility testing confirms the isolate is susceptible to oxacillin, cefazolin, vancomycin, and daptomycin. The patient has been receiving empiric intravenous vancomycin therapy since presentation. His medical history includes type $2$ diabetes mellitus and hypertension. $3$ years ago, he experienced a severe allergic reaction following a dose of oral amoxicillin; he rapidly developed diffuse urticaria, wheezing, and facial angioedema, which necessitated emergency administration of intramuscular epinephrine. He has no prior exposure to cephalosporin antibiotics. Currently, his vital signs are stable, and his serum creatinine is $0.9 \text{ mg/dL}$ . Based on current guidelines, which of the following is the most appropriate next step in the pharmacologic management of this infection?

Discontinue vancomycin and start intravenous oxacillin

Continue intravenous vancomycin

Discontinue vancomycin and start intravenous cefazolin

Discontinue vancomycin and start intravenous daptomycin

Discontinue vancomycin and start intravenous linezolid

Show answer & explanation

Answer: Discontinue vancomycin and start intravenous cefazolin

Answer

The most appropriate next step is to discontinue vancomycin and start intravenous cefazolin.

The correct answer is to switch the patient to intravenous cefazolin. This patient has a severe infection caused by methicillin-susceptible Staphylococcus aureus (MSSA). For MSSA infections, anti-staphylococcal beta-lactams (such as cefazolin) are significantly superior to vancomycin, demonstrating faster clearance of bacteremia, lower rates of clinical failure, and reduced mortality. Although this patient has a history of IgE-mediated anaphylaxis to amoxicillin (a penicillin), cefazolin is remarkably safe to administer. Cross-reactivity between penicillins and cephalosporins is not caused by the core beta-lactam ring itself, but rather by similarities in the R1 side chains. Cefazolin possesses a unique R1 side chain that is structurally distinct from all penicillins and almost all other cephalosporins. Therefore, it does not cross-react with penicillins, and current infectious disease and allergy guidelines strongly recommend the direct administration of cefazolin for MSSA infections in patients with penicillin anaphylaxis, without the need for prior skin testing or desensitization.

Step-by-Step Solution

1

Identify the pathogen and determine the optimal class of antibiotics for targeted therapy.

The patient has a severe, deep-seated infection (osteomyelitis and epidural abscess) caused by Methicillin-susceptible Staphylococcus aureus (MSSA).

For invasive MSSA infections, anti-staphylococcal beta-lactams (e.g., cefazolin, nafcillin, oxacillin) are the gold standard, as they provide vastly superior bactericidal activity compared to vancomycin, resulting in lower clinical failure and mortality rates.

2

Assess the impact of the patient's severe amoxicillin allergy on beta-lactam selection.

The patient had an IgE-mediated anaphylactic reaction to amoxicillin. Therefore, all penicillins (including oxacillin and nafcillin) are strictly contraindicated due to shared structural determinants.

Amoxicillin and oxacillin share the core penicillin beta-lactam structure, posing an unacceptably high risk of a recurrent life-threatening allergic reaction.

3

Evaluate the safety profile of cefazolin in the context of penicillin anaphylaxis.

Cefazolin can be safely administered to this patient despite the history of amoxicillin anaphylaxis.

Cross-reactivity between penicillins and cephalosporins is driven almost entirely by structural similarities in the R1 side chains, not the beta-lactam ring itself. Cefazolin possesses a completely unique R1 side chain that does not cross-react with penicillins or amoxicillin. Current guidelines recommend direct administration of cefazolin without prior testing in this scenario.

Key Concept

Patients with severe MSSA infections should be treated with an anti-staphylococcal beta-lactam rather than vancomycin to improve survival. Cefazolin possesses a unique R1 side chain and does not cross-react with penicillins, making it the preferred and safe definitive therapy even in patients with a history of severe, IgE-mediated anaphylaxis to penicillins.

Question 1165Question →

A 68-year-old woman is evaluated in the hospital for new-onset skin lesions. Six days ago, she was admitted for a right lower extremity deep vein thrombosis and started on a continuous intravenous unfractionated heparin infusion and oral warfarin. Two days ago, her platelet count was noted to have decreased from $260,000/\text{mm}^3$ on admission to $105,000/\text{mm}^3$ . Heparin was immediately discontinued, a serotonin release assay was sent, and an intravenous argatroban infusion was started. Warfarin was continued. Today, she complains of significant pain over her abdomen and both thighs. Physical examination reveals well-demarcated, erythematous, and purpuric lesions with central areas of black necrosis in these regions. Vital signs are stable.

Laboratory results today:
Hemoglobin: $11.2\text{ g/dL}$
Platelet count: $110,000/\text{mm}^3$
Prothrombin time (PT): $25\text{ sec}$
Activated partial thromboplastin time (aPTT): $68\text{ sec}$
INR: $2.4$

Which of the following is the most appropriate next step in management?

Discontinue warfarin and administer intravenous vitamin K

Continue current therapy and provide local wound care

Discontinue argatroban and initiate fondaparinux

Discontinue all anticoagulation and place an inferior vena cava filter

Administer intravenous methylprednisolone and diphenhydramine

Show answer & explanation

Answer: Discontinue warfarin and administer intravenous vitamin K

Answer

Discontinue warfarin and administer intravenous vitamin K

This patient's clinical presentation—well-demarcated, purpuric lesions progressing to black necrosis on the abdomen and thighs—is classic for warfarin-induced skin necrosis. This rare but serious complication typically occurs 3 to 5 days after initiating warfarin. It results from the rapid depletion of protein C, a vitamin K-dependent natural anticoagulant with a short half-life (approximately 8 hours), which declines significantly faster than the procoagulant factors II, IX, and X. This mismatch creates a transient, severe hypercoagulable state leading to microvascular thrombosis in subcutaneous fat. The risk is significantly magnified in patients with an underlying hypercoagulable state, particularly heparin-induced thrombocytopenia (HIT). In patients with HIT, warfarin is strictly contraindicated until the platelet count has fully recovered (typically >

150,000/\text{mm}^3

) because the combination of HIT-associated thrombosis and warfarin-induced protein C depletion can lead to catastrophic venous limb gangrene or skin necrosis. The most appropriate next step is to immediately discontinue the offending agent (warfarin), administer intravenous vitamin K to replenish protein C and reverse the hypercoagulable state, and continue a non-heparin anticoagulant (such as argatroban) to treat the underlying HIT and DVT.

Step-by-Step Solution

1

Analyze the patient's primary diagnosis based on the initial presentation and hospital course.

The patient developed a drop in platelets (>50%) after starting heparin, which is highly suspicious for heparin-induced thrombocytopenia (HIT). This was appropriately treated by stopping heparin and starting argatroban.

Establishing the underlying hypercoagulable state is crucial for understanding subsequent complications.

2

Evaluate the new-onset skin findings in the context of her medications.

The patient developed purpuric, necrotic skin lesions on her abdomen and thighs on day 6 of warfarin therapy. This is the classic presentation of warfarin-induced skin necrosis.

Identifying the etiology of the skin lesions determines the appropriate life-saving intervention.

3

Determine the optimal management for warfarin-induced skin necrosis in a patient with HIT.

Warfarin must be discontinued immediately. Intravenous vitamin K is administered to rapidly reverse the transient protein C depletion, while argatroban is continued to manage the HIT and underlying DVT.

Removing the offending agent and reversing its mechanism is the definitive treatment, while continuous non-heparin anticoagulation prevents systemic thrombosis.

Key Concept

Warfarin-induced skin necrosis in Heparin-Induced Thrombocytopenia (HIT)

Question 1166Question →

Match the following clinical scenarios of patients presenting with thrombocytopenia to the most likely underlying diagnosis.

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Answer

The correct matches are based on specific laboratory and clinical signatures: Scenario 1 represents Immune thrombocytopenia (ITP); Scenario 2 represents Thrombotic thrombocytopenic purpura (TTP); Scenario 3 represents Heparin-induced thrombocytopenia (HIT); and Scenario 4 represents Disseminated intravascular coagulation (DIC).

Each thrombocytopenic disorder has a distinct clinical and laboratory signature. ITP is a diagnosis of exclusion characterized by isolated thrombocytopenia. TTP presents with microangiopathic hemolytic anemia and end-organ damage due to ADAMTS13 deficiency. HIT presents with a paradoxical prothrombotic state 5-10 days after heparin exposure due to antibodies against the heparin-PF4 complex. DIC involves systemic activation of coagulation and consumption of factors, leading to prolonged PT/aPTT and elevated fibrin split products.

Step-by-Step Solution

1

Analyze the first scenario for isolated lab abnormalities.

The patient has severe thrombocytopenia but normal PT, aPTT, and peripheral smear.

Ruling out consumptive coagulopathy and microangiopathic processes points to peripheral platelet destruction (ITP).

2

Evaluate the second scenario for the classic TTP pentad.

The patient exhibits fever, neurologic symptoms, thrombocytopenia, renal failure, and schistocytes.

This combination of microangiopathic hemolytic anemia and multiorgan involvement is diagnostic for TTP.

3

Examine the third scenario for temporal clues and paradoxical findings.

The patient has a 50% platelet drop 6 days post-surgery with a new prothrombotic event (DVT).

Post-surgical patients receive heparin prophylaxis; the specific timeline and paradoxical thrombosis identify HIT.

4

Assess the fourth scenario for broad coagulation system failure.

The patient has an obstetric trigger (abruption) followed by bleeding, low platelets, prolonged PT/aPTT, and elevated D-dimer.

Widespread factor consumption and fibrinolysis confirm DIC.

Key Concept

Differential diagnosis of thrombocytopenia based on clinical presentation, coagulation panels, and peripheral blood smear findings.

Question 1167Question →

Match the following classic infectious disease clinical presentations with the most appropriate first-line antimicrobial therapy.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Gram-negative diplococci (meningitis) pairs with IV ceftriaxone. Lyme disease in pregnancy pairs with oral amoxicillin. Primary syphilis pairs with IM penicillin G benzathine. Uncomplicated cystitis pairs with oral nitrofurantoin.

Each clinical scenario presents a classic infectious disease that requires a specific first-line antimicrobial. Meningococcal meningitis requires CNS-penetrating IV ceftriaxone. Lyme disease in pregnancy requires amoxicillin to avoid tetracycline teratogenicity. Primary syphilis is definitively treated with IM penicillin G benzathine. Uncomplicated cystitis is safely managed with oral nitrofurantoin.

Step-by-Step Solution

1

Identify the likely pathogen and disease state for the first presentation.

Gram-negative diplococci in CSF indicates Neisseria meningitidis meningitis.

Recognizing the pathogen is necessary to select the appropriate targeted therapy.

2

Determine the appropriate treatment for meningococcal meningitis.

Intravenous ceftriaxone.

Third-generation cephalosporins are the standard of care for empiric and targeted therapy of N. meningitidis meningitis.

3

Identify the disease and patient constraints for the second presentation.

Erythema migrans indicates Lyme disease in a pregnant patient.

Pregnancy alters the standard treatment algorithm for early Lyme disease.

4

Select the appropriate alternative treatment for Lyme disease in pregnancy.

Oral amoxicillin.

Doxycycline is teratogenic, making amoxicillin the preferred safe alternative.

5

Identify the disease and stage for the third presentation.

Painless chancre indicates primary syphilis.

Accurate staging dictates the required dosage and duration of penicillin therapy.

6

Select the standard treatment for primary syphilis.

Intramuscular penicillin G benzathine.

A single dose of long-acting penicillin is curative for primary syphilis.

7

Identify the diagnosis for the fourth presentation.

Symptoms and positive nitrites without systemic signs indicate uncomplicated cystitis.

Differentiating uncomplicated cystitis from pyelonephritis dictates oral versus systemic/broad therapy.

8

Select the appropriate first-line therapy for uncomplicated cystitis.

Oral nitrofurantoin.

Nitrofurantoin concentrates well in the urine and is a preferred first-line agent.

Key Concept

Selection of first-line targeted antimicrobial therapy for common infectious diseases while accounting for patient-specific contraindications.

Question 1168Question →

A 45-year-old man presents to the outpatient clinic with a 2-day history of right calf pain and swelling. He recently returned from a 14-hour international flight. He has no chest pain, shortness of breath, or hemoptysis. His medical history is unremarkable, and he takes no medications.

Vital signs are:
Temperature: 37.0°C (98.6°F)
Heart rate: 78/min
Blood pressure: 125/80 mmHg
Respiratory rate: 14/min
Oxygen saturation: 98% on room air

Physical examination reveals a 4 cm increase in the circumference of the right calf compared to the left. The right calf is warm, tender to palpation, and exhibits mild erythema.

Laboratory panels reveal:
Hemoglobin: 14.8 g/dL
Mean corpuscular volume (MCV): 88 fL
Platelet count: 260,000/mm³
White blood cell count: 8,100/mm³
Serum creatinine: 0.9 mg/dL
Prothrombin time (PT): 12 seconds
Activated partial thromboplastin time (aPTT): 30 seconds

A comprehensive duplex ultrasonography of the right lower extremity demonstrates a non-compressible segment in the right popliteal vein.

Which of the following is the most appropriate next step in management?

Initiate oral apixaban therapy

Order a serum D-dimer assay

Administer intravenous broad-spectrum antibiotics

Administer intravenous furosemide

Reassure the patient and advise lower extremity elevation

Show answer & explanation

Answer: Initiate oral apixaban therapy

Answer

The most appropriate next step in management is to initiate oral apixaban therapy.

This patient has a confirmed, uncomplicated acute deep venous thrombosis (DVT) in the popliteal vein. He is hemodynamically stable, has normal renal function (creatinine 0.9 mg/dL), and has no active bleeding or high-risk comorbidities. The standard of care for an initial episode of proximal DVT is immediate therapeutic anticoagulation. Direct oral anticoagulants (DOACs) such as apixaban or rivaroxaban are currently preferred over warfarin because they have a rapid onset of action, do not require a parenteral bridging agent (like low-molecular-weight heparin), and do not require routine laboratory monitoring. Since the patient is completely stable with normal vital signs, he can be safely treated in the outpatient setting.

Step-by-Step Solution

1

Evaluate the clinical presentation and diagnostic findings.

The patient has signs, symptoms, and a confirmed ultrasound diagnosis of an acute right popliteal deep venous thrombosis (DVT).

To establish the correct diagnosis before initiating any targeted treatment.

2

Assess the patient's clinical stability and bleeding risk profile.

The patient is hemodynamically stable, has normal renal function, and normal baseline coagulation panels.

To determine the appropriate setting (inpatient vs. outpatient) and ensure there are no contraindications to anticoagulation.

3

Select the optimal therapeutic intervention.

Initiation of a direct oral anticoagulant (DOAC) such as apixaban.

DOACs are the standard of care for acute, uncomplicated DVT because they are highly effective, do not require laboratory monitoring, and can be administered orally in an outpatient setting.

Key Concept

Management of acute, uncomplicated deep venous thrombosis (DVT) with direct oral anticoagulants.

Question 1169Question →

A $65$ -year-old man visits the clinic reporting a $3$ -week history of profound fatigue, subjective fevers, and widespread joint pain. He notes that his wrists, knees, and ankles feel stiff and swollen. His past medical history is significant for ischemic cardiomyopathy with a reduced ejection fraction and chronic obstructive pulmonary disease. His daily medications include carvedilol, lisinopril, furosemide, hydralazine, and a tiotropium inhaler. Vital signs show a temperature of $37.9^\circ\text{C}$ ( $100.2^\circ\text{F}$ ), blood pressure of $128/78\text{ mmHg}$ , and heart rate of $76/\text{min}$ . Physical examination reveals mild symmetric effusions in the knees and wrists without overlying erythema. Cardiopulmonary examination reveals normal heart sounds without murmurs, and clear lung fields bilaterally.

Laboratory investigations reveal the following:

Laboratory Test	Result	Reference Range
Antinuclear antibodies (ANA)	Positive ( $1:640$ )	Negative
Anti-double-stranded DNA	Negative	Negative
Anti-histone antibodies	Positive	Negative
Rheumatoid factor (RF)	Negative	Negative
Thyroid-stimulating hormone (TSH)	$2.1\text{ \mu U/mL}$	$0.4-4.0\text{ \mu U/mL}$

Based on the patient's clinical presentation and laboratory findings, which of the following is the most appropriate next step in management?

Discontinuation of hydralazine

Administration of oral azithromycin and prednisone

Empiric intravenous vancomycin and ceftriaxone

Initiation of levothyroxine therapy

Initiation of methotrexate therapy

Show answer & explanation

Answer: Discontinuation of hydralazine

Answer

Discontinuation of hydralazine

The correct answer involves discontinuing hydralazine because the patient's clinical picture is highly characteristic of drug-induced lupus erythematosus (DILE). DILE presents with systemic symptoms such as fever, fatigue, and polyarthritis. The serological hallmark is a positive ANA and the presence of anti-histone antibodies, with a notable absence of anti-dsDNA antibodies (which are more specific to idiopathic systemic lupus erythematosus). Hydralazine is one of the most common medications known to cause DILE. The cornerstone of management is simply stopping the offending medication, which typically results in complete resolution of symptoms over several weeks.

Step-by-Step Solution

1

Analyze the clinical presentation and laboratory findings.

The patient has new-onset polyarthralgia, fatigue, and fever. Labs show positive ANA and positive anti-histone antibodies, but negative anti-dsDNA and negative RF.

Synthesizing symptoms with targeted serology is required to narrow the rheumatologic differential diagnosis.

2

Correlate the serologic profile with the patient's medication list.

The combination of positive ANA and anti-histone antibodies is the classic serologic signature for drug-induced lupus erythematosus (DILE). Hydralazine is a well-known high-risk medication for DILE.

Identifying the causative agent is the critical step in diagnosing a drug-induced autoimmune phenomenon.

3

Determine the appropriate therapeutic intervention.

The primary and most effective treatment for DILE is the removal of the offending drug.

Discontinuing hydralazine leads to the resolution of clinical symptoms, making it the most appropriate next step in management.

Key Concept

Drug-induced lupus erythematosus (DILE) classically presents with constitutional symptoms, arthralgias, positive ANA, and positive anti-histone antibodies, often triggered by medications like hydralazine or procainamide. The primary treatment is discontinuing the offending drug.

Estimated Time:1m 15s

Question 1170Question →

A 52-year-old man presents to the urgent care clinic due to severe pain, redness, and swelling in his left big toe. The symptoms started abruptly early this morning and have progressively worsened, making it difficult for him to walk. He has a medical history of hypertension, for which he takes hydrochlorothiazide. His temperature is 37.2°C (99.0°F), blood pressure is 135/85 mm Hg, and pulse is 88/min. Physical examination reveals a remarkably tender, erythematous, and warm left first metatarsophalangeal joint with significant swelling. An arthrocentesis is performed, and synovial fluid analysis demonstrates a leukocyte count of 25,000/mm³ with negatively birefringent, needle-shaped crystals under polarized light microscopy. Gram stain of the fluid shows no organisms, and his serum creatinine is 0.9 mg/dL. Which of the following is the most appropriate next step in the management of this patient?

Administration of oral naproxen

Initiation of daily allopurinol

Administration of intravenous vancomycin

Measurement of serum uric acid level

Measurement of antinuclear antibodies

Show answer & explanation

Answer: Administration of oral naproxen

Answer

Administration of oral naproxen

The correct answer is administration of oral naproxen. This patient presents with a classic acute flare of gout, characterized by severe, rapid-onset monoarthritis of the first metatarsophalangeal joint (podagra). The diagnosis is definitively established by synovial fluid analysis demonstrating needle-shaped, negatively birefringent monosodium urate crystals. The use of hydrochlorothiazide is a known risk factor, as thiazide diuretics decrease the renal excretion of uric acid. For the management of an acute gout flare, first-line therapies include nonsteroidal anti-inflammatory drugs (NSAIDs) like naproxen or indomethacin, colchicine, or glucocorticoids. Given the patient's normal serum creatinine and lack of stated contraindications, an NSAID is a highly effective and appropriate initial therapy to reduce acute inflammation.

Step-by-Step Solution

1

Analyze the clinical presentation and physical exam findings.

The patient has acute, highly inflammatory monoarticular arthritis of the first metatarsophalangeal joint (podagra), strongly suggesting a crystal-induced arthropathy or infectious etiology.

Identifying the clinical syndrome is the first step in formulating a differential diagnosis.

2

Interpret the synovial fluid analysis.

The fluid shows a moderately elevated leukocyte count (25,000/mm³) and negatively birefringent needle-shaped crystals, with a negative Gram stain.

These findings definitively confirm the diagnosis of acute gout caused by monosodium urate crystals and rule out septic arthritis.

3

Determine the most appropriate initial therapy for the confirmed diagnosis.

Oral NSAIDs (such as naproxen, indomethacin, or ibuprofen), colchicine, or systemic/intra-articular corticosteroids are the mainstays of acute gout treatment.

Since the patient has normal renal function (creatinine 0.9 mg/dL) and no stated contraindications, an oral NSAID is the most appropriate next step to quickly resolve the severe inflammation.

Key Concept

The diagnosis of acute gout is confirmed by the presence of negatively birefringent, needle-shaped monosodium urate crystals in synovial fluid. First-line therapy for an acute flare includes NSAIDs, colchicine, or corticosteroids.

Estimated Time:1m 0s

Question 1171Question →

A 72-year-old man with a history of a bioprosthetic aortic valve replacement three years ago is hospitalized due to a 4-week history of low-grade fever, progressive fatigue, and night sweats. On physical examination, his temperature is $38.2^\circ\text{C}$ ( $100.8^\circ\text{F}$ ), blood pressure is $118/76\text{ mmHg}$ , and heart rate is $92/\text{min}$ . A new grade 2/6 diastolic decrescendo murmur is heard at the right upper sternal border. Laboratory evaluation shows a leukocyte count of $14,500/\text{mm}^3$ and a serum creatinine of $1.1\text{ mg/dL}$ . Transesophageal echocardiography reveals a $1.4\text{ cm}$ vegetation on the prosthetic valve. Three sets of blood cultures obtained prior to antibiotic administration are all positive for *Enterococcus faecalis*. The patient is empirically started on intravenous vancomycin and gentamicin.

Antimicrobial susceptibility testing for the isolate demonstrates the following:
* Ampicillin: Susceptible
* Penicillin: Susceptible
* Vancomycin: Susceptible
* Gentamicin: High-level resistance

Which of the following is the most appropriate antimicrobial regimen for this patient?

Intravenous ampicillin and intravenous ceftriaxone

Continue intravenous vancomycin and intravenous gentamicin

Intravenous ampicillin and intravenous gentamicin

Intravenous vancomycin and intravenous ceftriaxone

Intravenous linezolid

Show answer & explanation

Answer: Intravenous ampicillin and intravenous ceftriaxone

Answer

The most appropriate regimen is intravenous ampicillin and intravenous ceftriaxone.

The correct answer is the combination of intravenous ampicillin and intravenous ceftriaxone. Enterococcal endocarditis requires bactericidal therapy, which is conventionally achieved through the synergistic combination of a cell-wall active agent (like ampicillin) and an aminoglycoside (like gentamicin). However, this isolate demonstrates high-level gentamicin resistance (HLAR). HLAR indicates that the synergistic bactericidal effect is lost, rendering the addition of an aminoglycoside not only ineffective but also unnecessarily nephrotoxic. The combination of ampicillin and ceftriaxone is a well-established, highly effective alternative. Ceftriaxone alone has minimal activity against Enterococcus, but it saturates specific complementary penicillin-binding proteins (PBPs), specifically PBP2 and PBP3, which allows ampicillin to exert a potent synergistic bactericidal effect. This combination is effective regardless of HLAR and avoids aminoglycoside-induced nephrotoxicity, making it the standard of care.

Step-by-Step Solution

1

Identify the primary diagnosis and pathogen.

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

Vegetation on a prosthetic valve with positive blood cultures establishes the diagnosis of infective endocarditis, requiring prolonged bactericidal therapy.

2

Evaluate the antimicrobial susceptibility results.

The isolate is susceptible to ampicillin but exhibits high-level resistance to gentamicin.

Targeted therapy must be selected based on susceptibility to maximize efficacy and minimize toxicity (antibiotic stewardship).

3

Determine the optimal bactericidal regimen.

Select ampicillin combined with ceftriaxone.

Enterococcal endocarditis requires synergistic bactericidal therapy. Because high-level gentamicin resistance abolishes synergy with aminoglycosides, the ampicillin plus ceftriaxone combination is required. Ceftriaxone saturates complementary penicillin-binding proteins (PBPs), restoring bactericidal synergy with ampicillin.

Key Concept

Treatment of Enterococcus faecalis endocarditis

Question 1172Question →

Match each clinical scenario describing a patient undergoing pharmacotherapy for a rheumatologic condition to the critical screening, prophylaxis, or adverse effect monitoring mandated by their specific medication.

Click a left item, then click its matching right item

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Answer

Pegloticase requires G6PD screening; Tofacitinib requires monitoring for cardiovascular events/thrombosis and herpes zoster; Cyclophosphamide requires Mesna prophylaxis for acrolein toxicity; Infliximab requires latent TB screening; Rituximab requires Hepatitis B screening.

Each immunosuppressive or immunomodulatory medication has a unique toxicity profile dictated by its mechanism of action. TNF inhibitors disrupt granulomas (TB risk). Rituximab depletes B-cells (HBV risk). Cyclophosphamide produces acrolein (bladder toxicity needing mesna). Pegloticase causes oxidative stress (hemolysis in G6PD deficiency). JAK inhibitors carry distinct risks for thrombosis and herpes zoster reactivation.

Step-by-Step Solution

1

Analyze the mechanism of action of pegloticase in gout management.

Pegloticase generates oxidative stress via hydrogen peroxide production, linking it to the need for G6PD deficiency screening.

G6PD deficient red blood cells cannot process oxidative stress, leading to hemolysis and methemoglobinemia.

2

Evaluate the specific boxed warnings associated with JAK inhibitors like tofacitinib.

JAK inhibitors are uniquely associated with increased risks of herpes zoster, venous thromboembolism (VTE), and major adverse cardiovascular events (MACE).

These specific adverse effects dictate pre-treatment cardiovascular risk stratification and zoster vaccination.

3

Recall the metabolism and target-organ toxicity of cyclophosphamide.

It metabolizes to acrolein, which concentrates in the bladder. Mesna acts as the specific antidote.

Mesna provides sulfhydryl groups that bind acrolein in the urinary tract, preventing hemorrhagic cystitis.

4

Identify the critical role of TNF-alpha in host immune defense.

TNF-alpha maintains granulomas; its inhibition by infliximab destabilizes them, risking tuberculosis reactivation.

Screening via IGRA or PPD is mandatory before initiating any TNF-alpha inhibitor.

5

Determine the unique infectious risks of severe B-cell depletion with rituximab.

Loss of antibody-mediated immunity drastically increases the risk of Hepatitis B reactivation.

Universal screening for HBsAg and anti-HBc is mandated prior to rituximab therapy to prevent fulminant hepatitis.

Key Concept

Essential pre-treatment screening, prophylaxis, and monitoring for targeted disease-modifying therapies in rheumatology.

Estimated Time:2m 30s

Question 1173Question →

Match each clinical presentation of a severe electrolyte abnormality to the most appropriate initial therapeutic intervention.

Click a left item, then click its matching right item

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Answer

Symptomatic hyponatremia is treated with hypertonic saline; hyperkalemia with ECG changes requires calcium gluconate; refractory hypokalemia needs magnesium sulfate; and severe hypercalcemia requires aggressive hydration with normal saline.

Each clinical scenario represents a distinct electrolyte emergency dictating a specific initial therapeutic priority. Symptomatic hyponatremia with neurological impairment mandates hypertonic saline to reduce cerebral edema. Hyperkalemia manifesting with widened QRS complexes requires immediate membrane stabilization with calcium gluconate. Hypokalemia that is refractory to standard potassium replacement suggests concomitant hypomagnesemia, requiring magnesium repletion to halt renal potassium wasting. Severe hypercalcemia causes profound diuresis and volume contraction, necessitating aggressive fluid resuscitation with normal saline to restore perfusion and promote urinary calcium excretion.

Step-by-Step Solution

1

Evaluate the patient presenting with severe hyponatremia and seizures.

Identify this as an acute neurological emergency caused by cerebral edema.

Neurologic symptoms in the setting of hyponatremia (SIADH) demand rapid but controlled correction of serum sodium using hypertonic saline to prevent irreversible brain injury.

2

Evaluate the patient with severe hyperkalemia and widened QRS complexes.

Recognize the imminent risk of fatal ventricular arrhythmias.

Immediate stabilization of the cardiac myocyte membrane with calcium gluconate is prioritized over interventions that shift or excrete potassium.

3

Evaluate the patient with hypokalemia that does not respond to intravenous replacement.

Identify concurrent hypomagnesemia as the barrier to potassium correction.

Magnesium deficiency prevents the closure of renal outer medullary potassium (ROMK) channels, leading to continuous potassium loss in the urine until magnesium is replenished.

4

Evaluate the patient with severe hypercalcemia and signs of severe dehydration.

Recognize that hypercalcemia-induced diuresis has caused massive volume depletion.

Aggressive isotonic fluid resuscitation is the first required step before administering definitive calcium-lowering therapies (like bisphosphonates or calcitonin) to dilute the calcium and restore glomerular filtration.

Key Concept

Initial emergency management of severe electrolyte disturbances

Question 1174Question →

A $72$ -year-old woman is evaluated on hospital day $3$ for ongoing medication management. She was initially admitted for a severe diabetic foot infection complicated by septic shock. On admission, her blood pressure was $85/50 \text{ mmHg}$ , which responded to aggressive intravenous fluid resuscitation. She was empirically started on broad-spectrum intravenous vancomycin and piperacillin-tazobactam. Due to initial profound lethargy and confusion in the emergency department, a comprehensive laboratory workup, including thyroid function tests, was obtained.

Today, the patient is alert, afebrile, and hemodynamically stable. Blood cultures and deep wound cultures from admission both exclusively grow methicillin-susceptible *Staphylococcus aureus* (MSSA). Laboratory results from the admission draw are now available and shown below:

Laboratory Test	Result	Reference Range
TSH	$0.15 \text{ mIU/L}$	$0.4-4.0 \text{ mIU/L}$
Free T4	$0.6 \text{ ng/dL}$	$0.9-1.7 \text{ ng/dL}$
Total T3	$55 \text{ ng/dL}$	$80-200 \text{ ng/dL}$

Which of the following is the most appropriate next step in management?

Discontinue vancomycin and piperacillin-tazobactam, begin intravenous cefazolin, and initiate levothyroxine supplementation

Discontinue vancomycin and piperacillin-tazobactam, begin intravenous cefazolin, and obtain an MRI of the pituitary gland

Continue vancomycin and piperacillin-tazobactam, and provide no thyroid-specific intervention

Discontinue vancomycin and piperacillin-tazobactam, begin intravenous cefazolin, and provide no thyroid-specific intervention

Discontinue vancomycin, continue piperacillin-tazobactam, and initiate levothyroxine supplementation

Show answer & explanation

Answer: Discontinue vancomycin and piperacillin-tazobactam, begin intravenous cefazolin, and provide no thyroid-specific intervention

Answer

Discontinue vancomycin and piperacillin-tazobactam, begin intravenous cefazolin, and provide no thyroid-specific intervention.

The most appropriate management for this patient involves two critical clinical decisions: proper antibiotic de-escalation and the correct interpretation of thyroid function abnormalities in critical illness. First, the patient's cultures grew methicillin-susceptible Staphylococcus aureus (MSSA). Continuing empiric broad-spectrum coverage (vancomycin and piperacillin-tazobactam) is contrary to antibiotic stewardship principles. Targeted, narrow-spectrum beta-lactams such as intravenous cefazolin or nafcillin are the superior agents for MSSA infections, providing better clearance and fewer adverse effects. Second, the patient's admission thyroid panel reveals low total T3, low free T4, and low TSH. This pattern, seen in the context of a severe stressor like septic shock, is classic for euthyroid sick syndrome (also known as non-thyroidal illness syndrome). It is characterized primarily by decreased peripheral conversion of T4 to T3, followed by central suppression of TSH and subsequent decreases in T4 as the illness severity worsens. Because this is a physiologic adaptation to stress and not a true thyroid pathology, no intervention (e.g., levothyroxine) or further diagnostic imaging (e.g., MRI) is indicated. Thyroid function typically normalizes weeks after recovery from the primary illness.

Step-by-Step Solution

1

Evaluate culture results and optimize antimicrobial therapy.

Cultures exclusively grew MSSA, indicating that broad-spectrum coverage with vancomycin and piperacillin-tazobactam is no longer appropriate.

Antimicrobial stewardship dictates transitioning to a narrow-spectrum, highly effective agent such as cefazolin or nafcillin for MSSA bacteremia.

2

Interpret the abnormal thyroid function tests in the context of the patient's severe acute illness.

The patient has low T3, low free T4, and low TSH obtained during an episode of septic shock.

This pattern is the hallmark of euthyroid sick syndrome (non-thyroidal illness syndrome), a physiologic adaptation to critical illness rather than true glandular pathology.

3

Determine the therapeutic requirement for the thyroid abnormalities.

No thyroid-specific intervention, imaging, or hormone replacement should be pursued.

Euthyroid sick syndrome resolves spontaneously as the underlying illness improves; exogenous thyroid hormone administration is not beneficial and can be harmful.

Key Concept

Management of euthyroid sick syndrome during critical illness and antibiotic stewardship for MSSA bacteremia

Question 1175Question →

An evaluation is requested for a 67-year-old male patient who reports a persistent sore on the bottom of his right foot for the past two months. He has a 15-year history of type 2 diabetes mellitus complicated by peripheral neuropathy. His vital signs include a blood pressure of 135/85 mm Hg, a heart rate of 76/min, and a temperature of 37.0°C (98.6°F). On physical examination, there is a 2.5-cm, painless ulcer on the plantar aspect of the right first metatarsal head. There is no significant surrounding erythema, warmth, or fluctuance. During exploration of the wound, a sterile metallic probe easily contacts hard, gritty tissue at the base of the ulcer. Laboratory testing reveals a leukocyte count of 8,200/mm³ and an erythrocyte sedimentation rate of 95 mm/h. Radiography of the right foot demonstrates focal periosteal elevation and frank cortical erosion of the underlying metatarsal head. Which of the following is the most appropriate next step in the management of this patient?

Perform a sterile bone biopsy for microbiologic culture

Administer broad-spectrum intravenous antimicrobial therapy

Obtain a superficial swab of the ulcer exudate for culture

Obtain magnetic resonance imaging of the right foot

Proceed with urgent surgical amputation of the first metatarsal

Show answer & explanation

Answer: Perform a sterile bone biopsy for microbiologic culture

Answer

Perform a sterile bone biopsy for microbiologic culture

The correct action is to perform a sterile bone biopsy. This patient has a confirmed case of diabetic foot osteomyelitis based on a positive probe-to-bone test and diagnostic plain radiographs showing cortical destruction. Because the patient is hemodynamically stable and has no systemic signs of severe infection (such as fever or extensive cellulitis), there is no indication for emergent empiric antibiotics. The standard of care is to withhold antimicrobial therapy until a bone biopsy can be obtained. This ensures accurate identification of the offending organism and its susceptibility profile, which is critical since diabetic foot infections are frequently polymicrobial or involve resistant organisms. Targeted therapy minimizes toxicity and adheres to principles of antimicrobial stewardship.

Step-by-Step Solution

1

Analyze the patient's clinical presentation and diagnostic findings.

The patient has a chronic diabetic foot ulcer with a positive probe-to-bone test, elevated ESR, and plain radiograph findings of cortical erosion, which are collectively diagnostic of osteomyelitis.

Establishing a definitive diagnosis is required before determining the appropriate management pathway.

2

Assess the patient's hemodynamic stability and the urgency of treatment.

The patient is afebrile, normocardic, and lacks severe surrounding cellulitis or signs of sepsis.

Stable patients do not require emergent empiric antibiotics, allowing time for optimal diagnostic sampling.

3

Select the optimal diagnostic step to guide antimicrobial therapy.

A sterile bone biopsy is chosen over superficial swabs or empiric treatment.

Bone biopsy provides a definitive microbiologic diagnosis, allowing for targeted antimicrobial therapy in accordance with antibiotic stewardship principles.

Key Concept

In clinically stable patients with diabetic foot osteomyelitis, obtaining a deep tissue or bone biopsy for microbiologic culture prior to initiating antimicrobial therapy is essential to ensure targeted, effective treatment and prevent the selection of resistant organisms.

Question 1176Question →

A hematology consultation service is reviewing the coagulation profiles of four adult patients, all of whom present with unexplained prolonged coagulation times on routine preoperative screening. Based on the specific specialized laboratory testing kinetics provided, match each patient's coagulation profile to the most accurate underlying pathophysiologic mechanism.

Click a left item, then click its matching right item

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Answer

Patient 1 matches acquired factor VIII inhibitor (time-dependent inhibition). Patient 2 matches lupus anticoagulant (phospholipid interference). Patient 3 matches Vitamin K deficiency (impaired gamma-carboxylation). Patient 4 matches Factor XI deficiency (autosomal recessive contact pathway).

The correct pairings accurately reflect the physiological and biochemical behavior of different hemostatic disorders in the laboratory setting. Mixing studies uniquely distinguish between physical absences of factors (which correct) and the presence of interfering antibodies (which do not correct, either immediately or after incubation).

Step-by-Step Solution

1

Analyze Patient 1's mixing study kinetics.

Initial correction with delayed prolongation indicates a time-dependent inhibitor.

Acquired Hemophilia A (Factor VIII inhibitor) autoantibodies are classically time- and temperature-dependent, initially appearing as a deficiency but revealing their inhibitory nature after incubation.

2

Analyze Patient 2's mixing study kinetics.

Immediate failure to correct indicates an inhibitor; correction with hexagonal phase phospholipid confirms lupus anticoagulant.

Lupus anticoagulants are autoantibodies that directly bind and neutralize the phospholipids used in the aPTT assay reagent, causing an immediate, non-time-dependent prolongation.

3

Evaluate Patient 3's coagulation profile.

Prolongation of both PT and aPTT that completely corrects on mixing indicates a multiple factor deficiency involving Factors II, VII, IX, and X.

These specific factors rely on Vitamin K as a cofactor for the gamma-glutamyl carboxylase enzyme, which allows them to bind calcium and phospholipid surfaces.

4

Evaluate Patient 4's coagulation profile.

Isolated aPTT prolongation that corrects and stays corrected indicates an intrinsic factor deficiency (Factor XI).

A pure deficiency lacks any inhibitory antibodies, so adding normal plasma fully and permanently replenishes the missing factor, resulting in a sustained normal aPTT.

Key Concept

Interpretation of time-dependent versus immediate mixing study kinetics to differentiate coagulation factor deficiencies from acquired inhibitors.

Estimated Time:2m 0s

Question 1177Question →

A $35$ -year-old man presents to the clinic with an $8$ -day history of a persistent cough. He states that the cough is productive of yellowish sputum and is occasionally accompanied by mild retrosternal chest soreness. He reports having a runny nose and a low-grade fever that resolved $3$ days ago. He has no significant past medical history and does not smoke. Vital signs are temperature $37.2^\circ \text{C}$ ( $99.0^\circ \text{F}$ ), blood pressure $122/78 \, \text{mmHg}$ , pulse $78/\text{min}$ , and respiratory rate $16/\text{min}$ . Pulse oximetry is $98\%$ on room air. Physical examination reveals normal tympanic membranes, mild pharyngeal erythema without exudate, and clear lung fields bilaterally without wheezes, rhonchi, or crackles. Which of the following is the most appropriate next step in management?

Observation and symptomatic management

Prescription for oral azithromycin

Prescription for oral amoxicillin

Prescription for oral levofloxacin

Sputum Gram stain and culture followed by targeted antibiotics

Show answer & explanation

Answer: Observation and symptomatic management

Answer

Observation and symptomatic management

The patient's presentation is classic for acute bronchitis, a lower respiratory tract infection primarily affecting the large airways. Over

90\%

of cases are caused by respiratory viruses (e.g., rhinovirus, influenza, coronavirus, RSV). The hallmarks are a cough lasting

1

to

3

weeks, often following a typical viral upper respiratory infection. Crucially, the presence of yellow or green sputum does NOT signify a bacterial infection; it simply reflects the presence of sloughed airway epithelial cells and neutrophils. Because the patient has normal vital signs and a normal pulmonary examination (no crackles, egophony, or tactile fremitus), community-acquired pneumonia is effectively ruled out. Therefore, chest radiography is unnecessary, and the most appropriate management is strict observation and symptomatic relief (e.g., NSAIDs, dextromethorphan, or guaifenesin). The administration of antibiotics for acute bronchitis is a major driver of antibiotic resistance and violates core principles of antimicrobial stewardship.

Step-by-Step Solution

1

Analyze the patient's clinical presentation and vital signs.

The patient has a cough lasting 8 days, purulent sputum, and prior URI symptoms, but normal vital signs and clear lung fields.

Differentiating uncomplicated acute bronchitis from community-acquired pneumonia requires assessing for systemic toxicity, abnormal vitals, and focal consolidation.

2

Determine the likely diagnosis.

The diagnosis is acute bronchitis, which is almost exclusively viral.

The absence of fever, tachycardia, tachypnea, and focal crackles makes bacterial pneumonia highly unlikely.

3

Select the appropriate management strategy based on antimicrobial stewardship principles.

Observation and symptomatic management are chosen.

Antibiotics do not improve outcomes in acute viral bronchitis. Purulent sputum alone is not an indication for antibiotics.

Key Concept

Antibiotic stewardship in acute bronchitis

Estimated Time:45s

Question 1178Question →

A 24-year-old woman presents to the clinic with a 6-week history of a painless, progressively enlarging mass in her right lower neck. She also reports intermittent fevers and drenching night sweats over the past month. Physical examination reveals a 3.5-cm, rubbery, mobile, non-tender lymph node in the right supraclavicular region. No other lymphadenopathy or hepatosplenomegaly is appreciated. Laboratory studies show a normal complete blood count, but the erythrocyte sedimentation rate is elevated at $65 \text{ mm/hr}$ . The physician suspects a hematologic malignancy. Arrange the following steps in the most appropriate chronological sequence for the diagnostic workup, staging, and initial management of this patient's most likely condition.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence is: Excisional biopsy, followed by FDG PET/CT scan, then baseline echocardiography and pulmonary function testing, and finally initiation of ABVD chemotherapy.

The patient presents with classic features of Hodgkin lymphoma (young adult, painless supraclavicular lymphadenopathy, B symptoms). The definitive first step is establishing a histologic diagnosis via excisional biopsy. Once diagnosed, disease extent must be mapped using FDG PET/CT (Ann Arbor staging). Because standard therapy (ABVD) utilizes doxorubicin and bleomycin, documenting baseline cardiac (echocardiography) and pulmonary (PFTs) reserve is mandatory. Finally, with diagnosis, staging, and safety clearance complete, chemotherapy can safely begin.

Step-by-Step Solution

1

Perform excisional lymph node biopsy

Histologic diagnosis of classic Hodgkin lymphoma

Required to evaluate node architecture and identify Reed-Sternberg cells. Fine needle aspiration is insufficient.

2

Perform FDG PET/CT scan

Determination of Ann Arbor stage

Once diagnosis is confirmed, imaging identifies all sites of involvement to dictate therapy intensity.

3

Assess baseline cardiopulmonary reserve

Echocardiogram and pulmonary function tests (PFTs)

ABVD contains doxorubicin (cardiotoxic) and bleomycin (pulmonary toxic). Baseline testing is mandatory before exposure.

4

Administer definitive therapy

Initiation of ABVD chemotherapy

Systemic treatment is initiated only after diagnosis, staging, and safety assessments are complete.

Key Concept

The sequential diagnostic and staging workup for classic Hodgkin lymphoma requires excisional biopsy for diagnosis, PET/CT for staging, and cardiopulmonary function testing prior to anthracycline and bleomycin exposure.

Estimated Time:1m 30s

Question 1179Question →

Match the following complex clinical scenarios and isolated pathogens with the most appropriate, definitive targeted antimicrobial therapy.

Click a left item, then click its matching right item

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Answer

The correct pairings match Enterococcus faecalis with HLAR to ampicillin and ceftriaxone; Candida auris to an echinocandin; visceral leishmaniasis to liposomal amphotericin B; VISA endocarditis to daptomycin; and pregnant syphilis patients with penicillin allergy to penicillin desensitization and therapy.

Each scenario tests a specific, high-level exception or requirement in infectious disease management. 1) E. faecalis with high-level aminoglycoside resistance requires ampicillin plus ceftriaxone for synergy. 2) Candida auris requires echinocandins due to prevalent multidrug resistance. 3) Visceral leishmaniasis is definitively treated with liposomal amphotericin B. 4) Vancomycin-intermediate S. aureus (VISA) requires a switch to an agent like daptomycin. 5) Pregnant patients with syphilis must receive penicillin, requiring formal desensitization if allergic.

Step-by-Step Solution

1

Analyze the Enterococcus faecalis scenario.

Identify the need for ampicillin and ceftriaxone.

High-level resistance to gentamicin precludes its use for synergy; ceftriaxone provides an alternative synergistic mechanism with ampicillin.

2

Evaluate the Candida auris bloodstream infection.

Select an echinocandin (e.g., micafungin).

C. auris has high rates of resistance to azoles, making echinocandins the initial treatment of choice per CDC guidelines.

3

Diagnose the parasitic infection causing massive splenomegaly.

Identify visceral leishmaniasis requiring liposomal amphotericin B.

Amastigotes within macrophages confirm the diagnosis, and liposomal amphotericin B is the first-line therapy.

4

Assess the treatment for MRSA with an elevated vancomycin MIC.

Choose intravenous daptomycin.

An MIC of 4 mcg/mL defines VISA, requiring a switch to a different bactericidal agent like daptomycin.

5

Determine the syphilis treatment for a pregnant, penicillin-allergic patient.

Opt for penicillin desensitization followed by penicillin G.

Penicillin is the only agent proven to effectively treat maternal infection and prevent congenital syphilis; desensitization is mandatory.

Key Concept

Targeted antimicrobial therapy for highly resistant pathogens and special populations

Question 1180Question →

Match each patient's clinical presentation to the most likely underlying hematologic or oncologic diagnosis.

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Answer

The presentations appropriately match as follows: the young woman with heavy menses and pica has iron deficiency anemia; the older man with bone pain, renal failure, and hypercalcemia has multiple myeloma; the lupus patient with a positive Coombs test has autoimmune hemolytic anemia; and the patient taking sulfa drugs with bite cells has G6PD deficiency.

Each clinical vignette provides classic, unequivocal features of a specific hematologic disorder allowing for straightforward diagnosis based on high-yield associations.

Step-by-Step Solution

1

Analyze the 28-year-old woman's clinical vignette.

Identified chronic blood loss (menses) resulting in microcytic anemia, low ferritin, and pica.

These findings are the definitive textbook presentation of iron deficiency anemia.

2

Analyze the 65-year-old man's clinical vignette.

Identified the CRAB criteria (hyperCalcemia, Renal failure, Anemia, Bone pain).

These combined end-organ damage findings in an older adult point directly to multiple myeloma.

3

Analyze the 40-year-old woman's clinical vignette.

Identified an autoimmune condition (SLE) causing hemolysis confirmed by an elevated reticulocyte count and a positive direct antiglobulin test.

A positive direct Coombs test in the setting of hemolysis indicates an immune-mediated destruction of red blood cells, diagnostic of autoimmune hemolytic anemia.

4

Analyze the 25-year-old man's clinical vignette.

Identified a specific oxidative drug trigger (trimethoprim-sulfamethoxazole) leading to hemolysis and the formation of bite cells.

Oxidative damage causing bite cells (from splenic macrophage removal of Heinz bodies) is highly specific for G6PD deficiency.

Key Concept

Classic presentations of highly tested hematologic and oncologic disorders

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