Fig. 1

Muscle morphological studies. Light microscopy. GSDIII morphological spectrum. a. H&E. Vacuolar myopathy with the majority of fibers harboring multiple and variably sized vacuoles present in both subsarcolemmal and central areas of the fibers. Note the presence of nuclear internalization or centralization and the proliferation of endomysial conjunctive tissue. b. mGT. The vacuoles appear filled with a faint eosinophilic material. The vacuoles confer a shabby appearance to the fibers. c. HE. Muscle sections showing at least two ring fibers (asterisks). The ring fibers are rounded, atrophic and surrounded by vacuoles suggesting that the myofibrils dissociated from the sarcolemma reorganize themselves with a different orientation. d. mGT. Ring fiber surrounded by a subsarcolemmal vacuole (asterisk). e. PAS. The section shows intensively stained areas of the cytoplasm corresponding to glycogen-laden vacuoles. The staining is intense also in areas of the cytoplasm without vacuoles. f. PAS. Section showing a milder staining intensity and some optically empty vacuoles. g. Acid Phosphatase. Normal acid phosphatase reaction demonstrating absence of lysosomal activation. Insert, intense acid phosphatase reaction in muscle from a patient with late onset Pompe disease is seen. h. ATPase 9.4 Section showing an equal distribution of the vacuoles in both type 2 (light fibers) and type 2 (dark fibers)