Inclusion body myositis with abundant ring fibers.

A 37-year-old male presenting with a 7-year history of leg weakness was found to have moderate weakness confined to the quadriceps and myopathic changes on electromyography. Serum creatine phosphokinase was 2130 units/liter. Biopsy of the quadriceps muscle revealed an inflammatory myopathy with cytoplasmic and nuclear filamentous inclusions characteristic of inclusion body myositis. An unusual finding was the large proportion of ring fibers along with severe atrophy and fibrosis. The pathogenesis of the ring fibers in this setting is discussed.