Mallory body-like inclusions in a hereditary congenital neuromuscular disease.

Subsequent to an earlier report on clinical and light microscopic data, peculiar Mallory body-like inclusions are described in muscle fibers of three genetically linked children. These Mallory body-like inclusions were unlike other well-defined intramuscular inclusions, such as nemaline, cytoplasmic, fingerprint, or sarcoplasmic bodies, but morphologically quite similar to hepatic Mallory bodies, because they were composed of three components: granular material and two types of filaments. Evidence is presented that these inclusions may contain desmin, the intermediate filament type characteristic of muscle. The exclusive appearance of these Mallory body-like inclusions in muscle biopsy specimens from three genetically related children of a large kinship emphasizes the uniqueness of these Mallory body-like inclusions in these muscle fibers as well as the special form of this congenital neuromuscular disorder.