Glycogen storage disease type 5 (GSDV) is a genetic disorder that prevents the body from breaking down glycogen. Glycogen is an important source of energy that is stored in muscle tissue. People with GSDV typically experience fatigue, muscle pain, and cramps during the first few minutes of exercise (exercise intolerance). Usually, when people with this disease rest after brief exercise they can resume exercising with little or no discomfort (a characteristic phenomenon known as “second wind”). The signs and symptoms can vary significantly and may include burgundy-colored urine, fatigue, exercise intolerance, muscle cramps, muscle pain, muscle stiffness, and muscle weakness. It is caused by mutations in the PYGM gene and is inherited in an autosomal recessive fashion. There is no cure or specific treatment but the disease can be managed with moderate-intensity aerobic training (e.g., walking or brisk walking, bicycling) and diet.
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