11/20/2006 Case 3: Mitochondrial myopathy

Diagnostic Notes:

The photomicrographs showed a muscle biopsy with severe atrophy of some fibers. There were scattered fibers with peripheral basophilia suggestive of ragged red fibers. Dr Sharer showed that the atrophic fibers were Type II based on immunohistochemical staining for Myo32 (positive in Type II fibers, negative in Type I) and slow Myosin (positive in Type I fibers, negative in Type II). Some of the atrophic fibers were so small as to constitute nuclear bags. Gomori Trichrome stains confirmed that there were ragged red fibers, and the peripheral cytoplasmic masses were also positive in NADH and SDH histochemical stains. Dr Hayes offered a diagnosis of the "Proximal Form of
Myotonic Dystrophy" . Dr Sharer indicated that he was still thinking about other diagnoses but that the case had been signed out as a Mitochondrial Myopathy.

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