Filling the Gap: Toward a Disease Activity Tool for Systemic Juvenile Idiopathic Arthritis

Systemic juvenile idiopathic arthritis (sJIA) accounts for 5%–15% of all children with chronic arthritis seen in Europe and North America, but is much more common in Asia, with reported frequency in India and Japan as high as 25% and 50%, respectively1. It is rather distinct from the other forms of JIA, owing to the association of arthritis with peculiar extraarticular symptoms, which include high-spiking fever, erythematous macular rash, diffuse lymphadenopathy, hepatosplenomegaly, and serositis, especially pleuritis and pericarditis2,3. Arthritis may be absent at onset and develop during the disease course, weeks, months, or rarely, years after the occurrence of systemic manifestations. Characteristic laboratory features include anemia (usually hypochromic and microcytic), leukocytosis, thrombocytosis, elevated immunoglobulins, increased erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), and hypoalbuminemia. Children with sJIA are uniquely susceptible to develop a potentially fatal hyperinflammatory complication known as macrophage activation syndrome4. Regular measurement of the level of disease activity in children with sJIA through the application of well-established tools is important in monitoring the disease course over time and in assessing the effectiveness of therapeutic interventions. However, clinical instruments specifically validated for use in sJIA are lacking. In recent randomized controlled trials of sJIA, the American College of Rheumatology Pediatric 30 criteria have been adapted for measuring therapeutic response by adding, besides the 6 core set variables, the demonstration of the resolution of fever (≥ 38°C) during the week preceding the evaluation5,6 or of the absence of fever (≥ 38.5°C) in the previous 2 weeks, and the reduction of systemic corticosteroid dosage by at least 10% from baseline in patients taking these medications7. Published criteria for clinically inactive disease8,9 and … Address correspondence to Prof. A. Ravelli, Pediatria II-Reumatologia, Istituto Giannina Gaslini, Via G. Gaslini 5, 16147 Genoa, Italy. E-mail: angeloravelli{at}gaslini.org