We established muscle-tissue cultures from biopsy of a patient with adult-onset acid maltase deficiency. Morphologically and biochemically, the newly grown fibers of the cultured muscle showed the same abnormalities as those of the biopsied muscle. Light microscopy showed multiple vacuoles filled with acid-phosphatase-positive material; on ultrastructural examination there was abnormal accumulation of glycogen in membrane-bound sacs (secondary lysosomes), some of which also contained dark membranous or homogeneous material. Acid maltase (pH 4.0), a lysosomal enzyme, was undetectable in either cultured or biopsied muscle by maltose hydrolysis, whereas acid phosphatase, also a lysosomal enzyme, was increased in both sources of muscle cells. Cultured muscle fibers demonstrate the same morphologic and biochemical abnormalities characteristic of biopsied muscle, supporting the concept of a biochemically distinct primary myopathy in man. (N Engl J Med 294:573–578, 1976).Adult-onset acid maltase deficiency, a defect in glycogenolysis, is a disease presenting clinically as skeletal-muscle weakness in the third to the fifth decade.12345In the case reported below, reproduction in cultured skeletal-muscle fibers of the morphologic and biochemical abnormalities present in the original muscle fibers (the only cells clinically affected in adult-onset acid maltase deficiency) demonstrated the reiteration of a biochemically distinct myopathy in cultured human muscle fibers. Case Report A 34-year-old man was admitted to the Medical Neurology Branch, National Institute of Neurological and Communicative Disorders and Stroke because of slowly progressive weakness for 2 1/2 years. Previously, he.
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