Association of Anti-HSC70 Autoantibodies with Cutaneous Ulceration and Severe Disease in Juvenile Dermatomyositis.

OBJECTIVES Juvenile dermatomyositis (JDM) is an inflammatory myopathy characterized by prominent vasculopathy. Anti-endothelial cell antibodies (AECA) are frequently detected in inflammatory and autoimmune diseases. We sought to determine whether AECA correlate with clinical features of JDM, and thus serve as biomarkers to guide therapy or predict outcome. METHODS Plasma samples from 63 patients with JDM, 49 patients with polyarticular juvenile idiopathic arthritis (JIA), and 40 juvenile healthy controls were used to detect anti-heat shock cognate 71 kDa protein (HSC70) autoantibodies, a newly identified AECA, in ELISA assays. Clinical features were compared between JDM patients with and without anti-HSC70 autoantibodies. RESULTS Anti-HSC70 autoantibodies were detected in 35% of patients with JDM, in 0% of patients with JIA (p< 0.0001), and in 0% of healthy donors (p< 0.0001). Both the presence of cutaneous ulcers (59% vs 17%, p< 0.002) and the use of wheelchairs and/or assistive devices (64% vs 27%, p< 0.007) were strongly associated with anti-HSC70 autoantibodies in JDM. High scores on the severity of myositis damage measures at the time of measurement of anti-HSC70 autoantibodies and an increased number of hospitalizations were also associated with anti-HSC70 autoantibodies. Intravenous immunoglobulin therapy was used more often in anti-HSC70 autoantibody-positive patients. CONCLUSION Anti-HCS70 autoantibodies are detected frequently in children with JDM and are novel myositis-associated autoantibodies correlating with disease severity.