A 10-year-old presents with daily fevers for 10 days, peakin…
A 10-year-old presents with daily fevers for 10 days, peaking late afternoons. She has salmon-colored, evanescent rash that appears with fever spikes. She reports diffuse joint pain but denies sore throat or cough. Exam reveals hepatosplenomegaly. Labs: markedly elevated ferritin, thrombocytosis, and leukocytosis. Blood cultures are pending. Which finding would most strongly support systemic JIA rather than infection?