A26: Longitudinal Disease Trajectory of Juvenile Dermatomyositis

Abstract

Background/Purpose:1) To determine the longitudinal disease activity trajectory of an inception cohort of Juvenile Dermatomyositis (JDM) patients, 2) To identify predictor(s) for longitudinal disease activity trajectory of JDM.Methods:A single‐center, inception cohort of juvenile dermatomyositis (JDM) patients (age of diagnosis <18 years old), recruited within 1 year of their initial presentation was studied. The patients were accrued from January 1991 to December 2010, in a JDM subspecialty clinic. Patients were evaluated at every clinic visit for disease activity with the modified Disease Activity Score (mDAS). Baseline disease features–DASm, swallowing difficulty, skin ulcer, calcinosis, duration of symptoms before evaluation, age and gender–were evaluated as predictors of the longitudinal trajectory of JDM. Time‐varying treatment effects were also tested. Longitudinal trajectory modeling was performed with mixed random effects modeling (random slopes).Results:Ninety‐five JDM patients (33 males, 35%) were studied. The median age of onset was 7.8 (25th–75th percentile (P): 4.9–12.1) years. The median mDAS score at presentation was 7 (25th–75th P: 6–9), the median skin subscale score was 3 (25th–75th P: 2–4), the median musculoskeletal subscale was 4 (25th–75th P: 3–6). The median duration of follow‐up was 4.6 (25th–75th P: 2.4–6.9) years. All patients in the cohort were treated with a standardized protocol comprising prednisone alone (before 2000) or methotrexate (MTX) and prednisone (after 2000). The disease trajectory of mDAS in this inception cohort followed a rapid reduction of activity within the first 2 years with a minor flare in disease activity beyond 2 years. Baseline nailfold abnormality predicted a slower improvement in mDAS trajectory. Higher baseline mDAS predicted faster improvement in mDAS trajectory. Treatment with MTX and prednisone predicted reductions in disease activity 3 and 6 months later respectively.Conclusion:Disease activity trajectory of JDM showed a general rapid reduction of mDAS followed by a small flare of disease activity beyond 2 years. Baseline nailfold abnormality and mDAS predicted future evolution of disease trajectory. The effects of treatment were observed only 3–6 months after.