LAUSR

BACKGROUND Persistent skin manifestations, especially calcinoses, contribute to morbidity in children with juvenile dermatomyositis (JDM). OBJECTIVE To compare the course of skin and muscle involvement and document frequency of calcinosis in JDM. METHODS Prospective cohort study of 184 untreated children with JDM (July 1971-May 2019) at a single children's hospital RESULTS: Disease activity scores (DAS) were persistently higher for skin vs muscle at all time points; clinical inactivity (DAS≤2) occurred later for muscle than skin. Among DAS-Skin vascular features, eyelid margin capillary dilatation was most frequent (54.3%) and persisted longest. Intravenous methylprednisolone reduced DAS-Skin more than oral prednisone at 12 months (p=.04). Overall, 16.8% (n=31) had calcifications, with 4.9% at enrollment. Despite therapy, 25.0% of calcifications recurred and 22.6% failed to resolve; of the latter, 71.4% (n=5) were present at enrollment. Children with persistent calcifications had longer duration of untreated disease than those whose calcifications resolved (mean, 12.5 months) (p<.001). Hydroxychloroquine did not improve DAS-skin (p=0.89). LIMITATIONS DAS does not quantify nailfold capillary dropout. CONCLUSIONS In JDM, skin disease presents with greater activity and is more recalcitrant to therapies than muscle disease. Early and aggressive treatment can limit the severity and persistence of calcifications identified later in the disease course.