Histological findings of muscle biopsy. Muscle biopsy showing diffuse degenerative changes with angular fibers (arrows) and variation in muscle fiber size. Mononuclear inflammatory cells consisting of lymphocytes are present, surrounding individual non necrotic fibers (arrowhead). Some foci of fat infiltration and connective tissue septa thickening can also be seen. H&E stain, 100 × original magnification.