[Ultrastructural and clinical studies in "inclusion body myositis" (author's transl)]

A non-hereditary slowly progressive neuromuscular disease occuring in a 39-year-old male, consisting of an asymmetrical wasting of the muscles of the shanks, is reported. Neither clinical nor electromyographic criteria can safely distinguish whether a primary neurogenic or a primary myogenic process is causally involved. The initial rise in serum CPK-activity indicates a myopathic origin. The lightmicroscopic aspect of the muscle-biopsy shows a muscular atrophy which resembles a primary neurogenic pattern with grouped clusters of atrophic fibers as well as a myopathic or rather myositic tissue-pattern with randomly scattered atrophic fibers. In addition there are numerous vacuoles which are equivalent to concentric lamellae of dense material in electronmicroscopy. Numerous fibrillary inclusions as well in the cytoplasm as in the cell-nucleus correspond to typical alterations in the so-called "inclusion body myositis". The disease is critically discussed as a nosological entity among neuromuscular disorders.