McArdle disease is a rare genetic disorder that affects the body’s ability to use muscle glycogen (stored glucose) as a source of energy for skeletal muscles. McArdle belongs to a class of diseases known as glycogen storage diseases (GSD)
The primary characteristic of McArdle disease is activity intolerance. Given that the vast majority of carbohydrates available to the muscle cells for consumption is in the form of muscle glycogen, McArdle patients have a lapse in energy production after a short period of physical activity. During this lapse in energy, they experience muscle pain, severe acute fatigue, and elevated heart rate. Following this debilitating lapse in energy, patients get a “second wind” when their muscle cells switch over to metabolism of fatty acids, but this only occurs after several minutes of continuous muscle activity. This lapse in energy sources can severely impact activities of daily living and occasionally result in severe rhabdomyolysis, which could lead to hospitalization and possible acute kidney failure requiring dialysis.
Children usually experience symptoms from around age 5, but most patients are not diagnosed until adulthood.
Current management of McArdle disease is to regularly undertake careful exercise in order to improve aerobic fitness. However, if not done properly this can lead to muscle breakdown.
At present, there are no approved drugs or treatment for McArdle disease.
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