Juvenile dermatomyositis: serial studies of circulating autoantibodies to a 56kD nuclear protein.

In this study we report that circulating antibodies recognising a 56kD protein, which is a component of large nuclear ribonuclear particles, are commonly found in children with juvenile onset dermatomyositis (JDM). These autoantibodies, as detected by Western blotting, were present in over 90% (24/26) of sera from JDM patients, which exceeds the number of patients with adult onset myositis who express this antibody (up to 85%). In addition, they were not found in healthy controls. Serial bleeds taken during the course of the disease in eleven children with JDM enabled us to follow the titre of anti-56kD autoantibodies. Sera were also tested by indirect immunofluorescence for anti-nuclear antibodies (ANA) using Hep2 cells as substrate. These studies revealed two distinct patient groups: Group 1 with anti-56kD antibody positive and ANA positive; and Group 2 with anti-56kD antibody positive and ANA negative. In Group 1 there was some correlation between disease activity and anti-56kD levels which was absent among patients in Group 2.