Muscular glycogenosis

Muscular glycogenosis (Orphanet code 206959) is a group term encompassing several rare inherited metabolic myopathies characterized by abnormal storage of glycogen within skeletal muscle tissue. These disorders result from deficiencies in various enzymes involved in glycogen synthesis or breakdown pathways within muscle cells. Because glycogen serves as a critical energy source for muscle contraction, its abnormal accumulation or impaired utilization leads to progressive muscle dysfunction. The primary body system affected is the musculoskeletal system, though cardiac muscle and other organs may also be involved depending on the specific subtype. Key clinical features commonly include exercise intolerance, muscle weakness (which may be progressive), muscle cramps, myalgia, and in some forms, episodes of rhabdomyolysis (acute muscle breakdown) with myoglobinuria. Some subtypes present with fixed proximal weakness resembling limb-girdle muscular dystrophy, while others manifest primarily as dynamic symptoms triggered by exertion. Elevated serum creatine kinase levels are a frequent laboratory finding. Treatment is largely supportive and varies by specific subtype. Management strategies may include dietary modifications (such as high-protein diets or controlled carbohydrate intake), supervised exercise programs, avoidance of strenuous activity to prevent rhabdomyolysis, and physical therapy. For Pompe disease (glycogen storage disease type II), enzyme replacement therapy with recombinant acid alpha-glucosidase is available. For most other muscular glycogenoses, no disease-specific therapies currently exist, and care focuses on symptom management and prevention of complications. Genetic counseling is recommended for affected individuals and their families.

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