Cumulative organ damage and prognostic factors in juvenile dermatomyositis: a cross-sectional study median 16.8 years after symptom onset

Objective. To describe cumulative organ damage in juvenile dermatomyositis (JDM) patients and to identify patient characteristics and early disease variables that predict organ damage. Methods. An inception cohort of 60 patients diagnosed with JDM from 1970 to 2006 was examined, median 16.8 (2.0-38.1) years after disease onset. Disease activity was measured by the disease activity score (DAS), organ damage by the myositis damage index (MDI) and physical function by the childhood or adult HAQ (CHAQ/HAQ). Medical records were reviewed for early disease variables at diagnosis, and 6 and 12 months post-diagnosis. Results. Fifty-four (90%) patients had a cumulative MDI total score >= 1 at follow-up (mean 4.2 +/- 3.1). Damage occurred most frequently in cutaneous, muscular and skeletal domains (77, 65 and 57%, respectively). Early predictors of damage were DAS and MDI 6 months post-diagnosis (beta=0.334; P=0.002 and 0.382, P<0.001, respectively). Follow-up time also correlated with MDI (P=0.010). Calcinosis, seen in 47% of the patients, was predicted by male gender [odds ratio (OR) 3.8; 95% CI 1.2, 12.1], and DAS 6 months post-diagnosis (OR 1.2; 95% CI 1.1, 1.4). The MDI score correlated with CHAQ/HAQ and DAS at follow-up (r(s)=0.355; P=0.005 and 0.446, P<0.001, respectively). The DAS decreased during the first-year post-diagnosis, whereas the MDI increased over time. Conclusions. The majority of JDM patients had cumulative organ damage at follow-up, which was predicted by high disease activity and organ damage 6 months post-diagnosis.