Type IV glycogenosis is usually a rapidly progressive disease of early childhood, causing death before 4 years of age. It is characterized by hepatosplenomegaly, cirrhosis, and chronic hepatic failure. Muscle involvement is generally overshadowed by liver disease. A mild non-infantile variant of type IV glycogenosis has been described in a few patients. In some of them, the patients suffered foremost from chronic progressive myopathy. We here report on a female patient aged 51 years who had experienced difficulties in climbing stairs for 2 years due to leg weakness. EMG revealed a myopathic pattern. The muscle biopsy findings revealed polyglycosan bodies. Biochemical investigation showed absence of branching enzyme in muscle but not in leukocytes and fibroblasts.