Autoantibodies against a nuclear 56 kDa protein: a marker for inflammatory muscle disease.

Antibodies to a 56 kDa nuclear protein have been found in the sera of 85% of patients with myositis using an immunoblotting technique. This auto-antibody appears to be relatively disease-specific though more frequently detectable in both adult and childhood onset dermatomyositis. In adult patients with myositis the anti-56 kDa antibody level reflects disease activity. This antibody is thus much more frequently found than previously described disease-specific autoantibodies in patients with myositis such as the Jo-1 antibody, and may represent a useful diagnostic aid in patients with muscle weakness.