Glycogen storage disease type V is a metabolic disorder, more specifically a glycogen storage disease, caused by a deficiency of myophosphorylase, the muscle isoform of the enzyme glycogen phosphorylase. This enzyme helps break down glycogen (a form of stored carbohydrate) into glucose so that it can be utilized within the muscle cell. more...
GSD type V is also known as McArdle's disease or muscle phosphorylase deficiency. The disease was first diagnosed in 1951 by Dr. Brian McArdle of Guy's Hospital, London.
People with this disease experience difficulty when their muscles are called upon to perform relatively brief yet intense activity. The inability to break down glycogen into glucose results in an energy shortage within the muscle, resulting in muscle pain and cramping, and sometimes causing serious injury to the muscles. In addition, rhabdomyolysis—the breakdown of muscle tissue—can cause myoglobinuria, a red-to-brown-colored urine. The myoglobinuria can cause kidney damage. The disease is hereditary and is inherited as an autosomal recessive trait. Anaerobic exercise must be avoided but regular gentle aerobic exercise is beneficial.
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