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Washington University Experience | MUSCLE | Myopathies with Mitochondrial Pathology | 31A1B (Case 31) EM003 - Copy

Pale subsarcolemmal vacuoles contain dense punctate inclusions. Electron microscopy demonstrates many muscle fibers with mitochondrial abnormalities. There are subsarcolemmal collections of large numbers of mitochondria which vary individually in appearance. The most common abnormality other than increased collections and numbers are variations in size and shape, many enlarged over normal size mitochondria which are present in rare fibers. Many cristae are enlarged and dense. A few collections are markedly elongated and thinned with long cristae. Very rare matrix densities are identified. A few mitochondria appear vacuolated and enlarged with thin rims which do not appear to represent artifact. The vacuoles seen in plastic sections are identified and contain dense small cytosomes, possibly derived from degraded mitochondria with rare collections of membranous aggregates. Many mitochondria, collections as well as individual forms, are associated with small vacuoles containing fat. There are dense organelles which resemble lipopigment and contain lipidic foci and granular material, but not obvious mitophagy. (electron micrographs)

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