Fig. 2

Histopathologic and ultrastructural findings of skeletal muscle biopsy. Antemortem skeletal muscle biopsy showed mild variation in muscle fiber diameter by light microscopy on H&E-stained sections a Dual staining for cytochrome C oxidase (COX) and succinate dehydrogenase (SDH) showed fibers with abnormal subsarcolemmal accumulations of mitochondria and a single COX negative fiber b Modified Gomori trichrome staining demonstrated the abnormal subsarcolemmal mitochondrial accumulation without evidence of ragged red fibers c Ultrastructural examination of myofibers showed aggregates of mitochondria in the subsarcolemmal space (black arrow) d, corresponding with the subsarcolemmal pads seen by light microscopy and within the sarcomeric apparatus e. Individual mitochondria exhibited ultrastructural abnormalities, including enlargement and formation of irregular cristae f Size bars are 100 μm (panels a-c), 2 μm (panel d), 1 μm (panel e), and 400 nm (panel f)