Glycogen storage disease type V (GSDV); Myophosphorylase deficiency; Muscle glycogen phosphorylase deficiency; PYGM deficiency
McArdle syndrome is the inability to break down glycogen. Glycogen is an important source of energy that is stored in muscle tissue.
McArdle syndrome is caused by a defect in a gene that makes an enzyme called glycogen phosphorylase. As a result, the body cannot break down glycogen in the muscles.
The disease is an autosomal recessive genetic disorder. This means that you must get a copy of the nonworking gene from both parents. A person who gets a nonworking gene from only one parent usually does not develop this syndrome. A family history of McArdle syndrome increases the risk.
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