McArdle syndrome is the inability to break down glycogen. Glycogen is an important source of energy that is stored in muscle tissue.

Glycogen storage disease type V (GSDV); Myophosphorylase deficiency; Muscle glycogen phosphorylase deficiency; PYGM deficiency

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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McArdle syndrome Symptoms

Review Date: 03/29/2011
Reviewed By: A.D.A.M. Editorial Team: David Zieve, MD, MHA, and David R. Eltz. Previously reviewed by Chad Haldeman-Englert, MD, Division of Human Genetics, Children's Hospital of Philadelphia, Philadelphia, PA. Review provided by VeriMed Healthcare Network (1/21/2010).

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)