Fig. 2

Microscopic findings of muscle biopsy specimen showed mitochondrial toxicity. a Muscle fibers are of variable size and irregular shape, and there are many atrophic and degenerating muscle fibers. (HE, magnification × 200); b A lot of red granular changes in atrophic fibers. (modified Gomori trichrome stain, magnification × 200); c Increased enzyme activities in many atrophic fibers. (succinic dehydrogenase, magnification × 200); d Many muscle fibers are deficient for enzyme activities. (cytochrome oxidase stain, magnification × 200)