[A case of acid maltase deficiency (juvenile type)--immunohistochemical and biochemical study]

A 22-year-old housewife was referred to us for review of progressive proximal muscle weakness which started at 15 years of age. A biopsy of left rectus femoris muscle showed acid phosphatase positive vacuoles partly filled with PAS-positive material. Acid maltase activity of the cultured fibroblasts was pathologically low at 0.4 nmol/mg protein considering 161.0 +/- 32.4 nmol/mg protein as a normal range. A diagnosis was made of acid maltase deficiency (juvenile type). Western blot using anti-acid maltase polyclonal antibody revealed 115 and 70 kDa bands in control muscles, where as only the 115 kDa band, a presumable precursor of the enzyme, was visualized in the patient. By immunohistochemistry using the same antibody the epitope was localized to the acid phosphatase positive vacuoles and immunoelectron microscopy demonstrated the acid maltase immunoreactivity within lysosomes. We concluded that the protein precursor unable to proceed into mature enzyme can access to lysosomes from endoplasmic reticulum through Golgi complex in the present case.