The arthritis of inflammatory childhood myositis syndromes

Objective. Arthritis has been an associated finding in juvenile dermatomyos itis (JDM), but its prevalence. course, and response to therapy has not bee n well described. We investigated the frequency, course. and clinical and r adiographic features in a large cohort of patients with JDM. Methods. The charts of 94 patients with idiopathic myositis (1984-99) were reviewed: 80 JDM, 3 juvenile polymyositis (JPM), 5 amyopathic JDM, and 6 ov erlap myositis syndromes. Compiled data included demographics, clinical fea tures, a detailed description of the arthritis, investigations (radiographs , autoantibodies), course, and response to therapy. All radiographs were in dependently reviewed by a single radiologist. Results. Sixty-one percent (95% CI 50-72%) of patients with JDM had arthrit is. The arthritis was reported a median 4.5 mo (range -73.6 to 76.6 mo) aft er the JDM onset. When compared to patients with no arthritis, the occurren ce of arthritis was not significantly related to sex, race, positive antinu clear antibody or rheumatoid factor, calcinosis, nodules, vasculitis, or Ra ynaud's phenomenon. The initial involvement was pauciarticular in 67% and p olyarticular in 33%. In the pauci group, asymptomatic knee effusions were t he predominant finding (n = 19, 58%), and in 18 patients may have been the result of steroid therapy. Two patients evolved from a pauci onset to a pol yarticular course. All responded to therapy (corticosteroids; 47 were takin g other medications) with remission of the arthritis within a median of 2.0 mo (range 0.1-64.5 mo). However, the arthritis recurred in 39% as the cort icosteroids were tapered. Four patients with JDM eventually required cortic osteroid wrist injections, with resolution of the arthritis. The arthritis was nonerosive in all cases. No patient with JPM had arthritis. Three of 5 patients with amyopathic JDM and 4 of 6 with overlap myositis syndrome had a nonerosive polyarthritis. Conclusion. Nonerosive arthritis involving the knees, wrists, elbows, and f ingers is a frequent manifestation of JDM and other idiopathic childhood my ositis. The arthritis is seen early in the course of JDM and often responds to treatment. However, the arthritis may recur with tapering of corticoste roids despite remission of the JDM. In a significant proportion of JDM case s, arthritis is the major sequela and may warrant further medical therapy o r intraarticular corticosteroid injections.