A 5-year-old girl presents with 4 joints affected (knees and ankles, bilateral), morning stiffness, a salmon-colored evanescent rash appearing with fever spikes, and daily fever spikes >39°C for 3 months. Serum ferritin is 18,000 ng/mL and ANA is negative. The MOST likely diagnosis is:

• A Oligoarticular JIA
• B Systemic JIA (sJIA) — formerly Still's disease ✓
• C Polyarticular JIA (RF-positive)
• D Reactive arthritis (Reiter syndrome)

Explanation

Systemic juvenile idiopathic arthritis (sJIA) is diagnosed by quotidian (daily) fever spikes ≥39°C for ≥2 weeks, arthritis in ≥1 joint, and at least one of: salmon-pink evanescent rash (classic), hepatosplenomegaly, generalized lymphadenopathy, or serositis. Markedly elevated ferritin (often >10,000 ng/mL) is characteristic and can herald macrophage activation syndrome (MAS) — a life-threatening complication. ANA and RF are typically negative in sJIA.

Reference: Ghai Essential Pediatrics, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.