Inclusion body myositis. A "slow-virus" infection of skeletal musculature?

We report the case of a 56-years old patient with clinical symptoms of an unresolved neuromuscular disease. The light microscopic studies of a muscle biopsy from the m. triceps shows the picture of a diffuse muscular atrophy. By electron microscopy, myelin-like degeneration zones with tubular-filamentous inclusions can be shown in the cytoplasma of the atrophic muscle cells. These filamentous structures correspond morphologically to the nucleocapside of paramyxoviruses. These results lead, even without the proof of inflammatory cells, to the diagnosis of an "inclusion body" myositis also taking into account the clinical and electrophysiological findings.