“Megaconial” mitochondria observed in a case of chronic polymyositis

Summary Bizarre configurations of muscle mitochondria containing paracrystalline inclusions were demonstrated in a clinically and pathologically typical case of chronic polymyositis with Raynaud's syndrome. The probable mechanism of formation of these abnormal mitochondria was discussed. From the accompanied alterations in the same fibers, i.e. focal assembly of sarcoplasmic reticulum, membranous profiles, miniature mitochondria, and vesicular nuclei with prominent nucleoli, the overall phenomena were interpreted as a process of atypical regeneration.The detail of the subunits of the paracrystalline inclusions was described and considered to be filamentous structures arranged in double helix. Non-specificity of these mitochondrial abnormalities was evident in 19 other reported cases with a wide range of symptoms, signs, clinical diagnosis, age, and sex distribution. The mitochondrial alterationsper se do not, therefore, reflect any specific muscle disease. Observations of myxovirus-like structures in all 3 biopsy specimens in the present case is discussed in conjunction with the concurrent abnormal mitochondria.Presented at the scientific session of the annual meeting of the American Academy of Neurology, San Francisco, April, 1967.Supported in part by U. S. Public Health Service grants GM09387, G-256-6, and 5 SOI-FR-05433-07.