Skin disease is more recalcitrant than muscle disease: A long-term prospective study of 184 children with juvenile dermatomyositis

Background: Persistent skin manifestations, especially calcinoses, contribute to morbidity in children with juvenile dermatomyositis. Objective: To compare the course of skin and muscle involvement and document frequency of calcinosis in juvenile dermatomyositis. Methods: Prospective cohort study of 184 untreated children with juvenile dermatomyositis (July 1971 to May 2019) at a single children's hospital. Results: Disease Activity Scores (DASs) were persistently higher for skin versus muscle at all points; clinical inactivity (DAS ≤2) occurred earlier for muscle than skin. Among vascular features for DAS for skin, eyelid margin capillary dilatation was most frequent (54.3%) and persisted longest. Intravenous methylprednisolone reduced DAS for skin more than oral prednisone at 12 months (P =.04). Overall, 16.8% of patients (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 for skin (P =.89). Limitations: DAS does not quantify nailfold capillary dropout. Conclusions: In juvenile dermatomyositis, 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.