INCLUSION-BODY MYOSITIS - EXPLANATION FOR POOR RESPONSE TO IMMUNOSUPPRESSIVE THERAPY

We treated eight patients who had inclusion body myositis (IBM) with o ral prednisone therapy, and we performed muscle biopsies before and af ter treatment. We documented the patients' clinical response to therap y and changes in serum CK. Although the serum CK level fell, muscle st rength worsened after prednisone treatment. In addition, while inflamm ation decreased in the muscle biopsy specimens, the number of vacuolat ed and amyloid-positive fibers increased after oral prednisone therapy . These observations indicate that the inflammatory response in IBM ma y play a secondary role in the pathogenesis of IBM. The unique finding s of intracellular amyloid deposits and rimmed vacuoles distinguishing IBM from other inflammatory myopathies, and recognition that suppress ion of inflammation has no effect on the clinical course, suggest that IBM, may represent a degenerative muscle disorder.