A 7-year-old girl presents with arthritis in 6 joints (both knees, both wrists, and MCP joints bilaterally) for 8 weeks. Temperature spikes occur twice daily reaching 39.5°C, each episode lasting 2–4 hours, associated with a salmon-colored evanescent rash during the fever. Ferritin is 45,000 ng/mL, and white cell count is 28,000/µL. ANA and RF are negative. What is the MOST likely diagnosis, and what systemic life-threatening complication must be screened for?

• A RF-positive polyarticular JIA; screen for pericarditis
• B Systemic lupus erythematosus; screen for renal involvement
• C Reactive arthritis following streptococcal infection; screen for carditis
• D Systemic JIA (sJIA); screen for macrophage activation syndrome (MAS) ✓

Explanation

Systemic juvenile idiopathic arthritis (sJIA) is characterized by the triad of arthritis, daily quotidian fever (salmon-pink evanescent rash during fever spikes), and systemic features. The markedly elevated ferritin (>10,000 ng/mL) is a key clue. The most feared complication is macrophage activation syndrome (MAS), a form of hemophagocytic lymphohistiocytosis (HLH), presenting with falling WBC and platelet counts, rising ferritin, and hepatosplenomegaly despite continued fever. Early recognition is critical as MAS carries 30–50% mortality if untreated. Ferritin >684 ng/mL in a child with sJIA should prompt MAS screening.

Reference: Ghai Essential Pediatrics, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.