McArdle syndrome

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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; PGYM 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 get a copy of the defective gene from both parents. A person who gets a defective gene from only one parent usually does not develop this syndrome. A family history of McArdle syndrome increases the risk.

The disease usually starts when a person is in their 20s or 30s, but there is a very rare form that begins in infants.

Review Date: 10/15/2008
Reviewed By: Diana Chambers, MS, EdD, Certified Genetics Counselor (ABMG), Charter Member of the ABGC, University of Tennessee, Memphis, TN. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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