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Washington University Experience | MUSCLE | Myopathies with Mitochondrial Pathology | 33B0 Case 33 Denoument
Cytochrome oxidase shows many fibers with reduced or absent staining. SDH shows a comparable number of fibers with increased staining. ---- NP/NM Comment: This represents chronic mitochondrial myopathy, evidenced by the ragged red and blue fibers on Gomori trichrome and SDH, respectively, and the many fibers with reduced or absent staining on COX. Chronic features include the abnormal variation in fiber size with hypertrophied fibers, fibers with internal nuclei, increased endomysial connective tissue, and perimysial fat. A second muscle fiber pathology is the presence of fibers with vacuoles that show staining on Gomori trichrome and acid phosphatase. In addition to the vacuoles lacking basophilic debris on H&E and Congo red, there is no inflammation or immune features to suggest an IM-VAMP to account for the vacuoles with mitochondrial pathology. Given these changes and the fibers with increased staining on PAS, glycogen pathway testing, including acid maltase testing, could be performed. Pending results of these analyses and the remaining tissue available, the vacuoles could also be further characterized by dystrophy related protein stains and/or aggregate stains. No further workup results are in our files.
