An evaluating physician assesses a 31-year-old female in the urgent care clinic. She repor… — USMLE Step 2 CK

An evaluating physician assesses a 31-year-old female in the urgent care clinic. She reports a two-week duration of severe joint pain affecting her wrists and knees, accompanied by daily fevers. She states her temperature consistently spikes to $39.5^{\circ}\text{C}$ ( $103.1^{\circ}\text{F}$ ) in the late afternoon and returns to normal by the following morning. During these febrile episodes, she notices a faint, salmon-colored rash on her trunk that completely resolves once the fever breaks. Her medical history is notable for bipolar disorder, which is currently managed with lithium and a recently added selective serotonin reuptake inhibitor.

Vital signs are temperature $39.4^{\circ}\text{C}$ ( $102.9^{\circ}\text{F}$ ), blood pressure $118/76\text{ mm Hg}$ , pulse $112/\text{min}$ , and respirations $18/\text{min}$ . Physical examination confirms a macular, salmon-colored rash on the chest and abdomen. The wrists and knees exhibit mild effusions and tenderness to palpation bilaterally.

Laboratory studies show:

Test	Value	Reference Range
Leukocytes	$18,500/\text{mm}^{3}$ (85% neutrophils)	$4,000-11,000/\text{mm}^{3}$
Hemoglobin	$11.2\text{ g/dL}$	$12.0-15.5\text{ g/dL}$
Platelets	$450,000/\text{mm}^{3}$	$150,000-400,000/\text{mm}^{3}$
Ferritin	$7,500\text{ ng/mL}$	$15-200\text{ ng/mL}$
Rheumatoid factor	Negative	Negative
Antinuclear antibody	Negative	Negative
TSH	$5.5\text{ }\mu\text{U/mL}$	$0.4-4.0\text{ }\mu\text{U/mL}$
Free T4	$1.2\text{ ng/dL}$	$0.9-1.7\text{ ng/dL}$

Blood and urine cultures obtained 48 hours ago demonstrate no growth.

Which of the following is the most appropriate next step in the management of this patient's current symptoms?

Initiation of oral prednisoneAnswer
B
Initiation of high-dose ibuprofen
C
Administration of intravenous vancomycin and cefepime
D
Initiation of oral levothyroxine
E
Discontinuation of lithium while maintaining the selective serotonin reuptake inhibitor

Answer

The correct answer is the initiation of oral prednisone.

Adult-onset Still's disease (AOSD) is a systemic autoinflammatory disorder characterized by the classic triad of quotidian fevers, an evanescent salmon-colored rash, and inflammatory polyarthritis. The markedly elevated ferritin level (often

>3,000\text{ ng/mL}

) and neutrophilic leukocytosis in the absence of infection (negative cultures) strongly support this diagnosis. Although nonsteroidal anti-inflammatory drugs (NSAIDs) are typically the initial treatment for mild to moderate AOSD, this patient is actively taking lithium. NSAIDs significantly decrease the renal clearance of lithium, risking acute, severe lithium toxicity. Therefore, the safest and most appropriate next step to induce remission in this patient is the initiation of systemic glucocorticoids (e.g., oral prednisone).

Step-by-Step Solution

Analyze the patient's presentation (quotidian spiking fevers, evanescent salmon-colored rash, polyarthritis) and laboratory results (extreme hyperferritinemia, neutrophilic leukocytosis).

The clinical picture strongly indicates a diagnosis of Adult-onset Still's disease (AOSD).

Recognizing the classic clinical triad and supporting biomarkers is necessary to differentiate AOSD from sepsis or other autoimmune conditions.

Determine the standard first-line therapies for mild-to-moderate AOSD.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are typically the first-line pharmacotherapy.

NSAIDs effectively control the fever and arthritis in many patients with AOSD.

Review the patient's current medication list to ensure the selected therapy is safe.

The patient is taking lithium for bipolar disorder. NSAIDs interact dangerously with lithium.

NSAIDs decrease the renal clearance of lithium, which can rapidly lead to life-threatening lithium toxicity.

Select the next most appropriate, safe immunosuppressive therapy.

Oral prednisone (a systemic glucocorticoid) is selected.

Glucocorticoids are highly effective for AOSD and avoid the dangerous pharmacokinetic interaction with lithium.

Key Concept

Diagnosis of Adult-onset Still's disease and management of pharmacotherapy around dangerous drug-drug interactions (NSAIDs and lithium).

Estimated Time:1m 30s

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