Myopathy with deficient chondroitin sulfate C in connective tissue

H&E stain	ATPase pH 9.4 stain
Muscle fiber morphology Variability in fiber size Small fibers are angular & type 2 (Dark on ATPase pH 9.4) No active myopathic changes
H&E stain	Acid phosphatase stain	Alkaline phosphatase stain
Connective tissue changes Perivascular inflammatory infiltrate: Rare Perimysial cells staining with acid phosphatase: Occasional Perimysium staining with alkaline phosphatase
Antibody to Chondroitin sulfate C: Immunoperoxidase stain Patient muscle before treatment	Antibody to Chondroitin sulfate C: Immunoperoxidase stain Normal muscle	Antibody to Chondroitin sulfate C: Immunoperoxidase stain Patient muscle after corticosteroid treatment
Chondroitin sulfate staining in muscle endomysium Normally abundant in skeletal muscle endomysium Absent in patient muscle before treatment Returns to near normal after corticosteroid treatment