Fig. 2

Histopathological characterization of the patient. A H&E staining revealed slight variability in muscle fiber size, with dark subsarcolemmal staining in several fibers. B MGT staining revealed numerous RRFs (arrow). C ORO staining highlights extensive lipid droplet accumulation (asterisks). D COX staining demonstrates COX-negative fibers (arrow). E SDH staining shows increased SDH activity in many fibers (arrow). F Combined COX-SDH staining identifies fibers with both COX deficiency and SDH positivity (arrow). H&E, hematoxylin and eosin; MGT, modified Gomori trichrome; RRFs, ragged red fibers; ORO, Oil Red O COX, cytochrome c oxidase; SDH, succinate dehydrogenase; RBFs, ragged blue fibers. Scale bar: 50 μm