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McArdle syndrome (glycogen storage disease type V) |
| Overview Symptoms Treatment Prevention |
| Alternative Names: |
| Glycogen storage disease type V; Muscle phosphorylase deficiency |
| Symptoms: |
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Muscle pain, cramps, and stiffness during exercise are the primary symptoms of McArdle syndrome. Other symptoms include the following:
Symptoms usually do not begin until the affected person has reached adulthood. Avoiding strenuous exercise decreases the severity of these symptoms and of the disease. |
| Signs and tests: |
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Brief, intense exercise typically does not lead to an increase in blood lactic acid. Tests may reveal the presence of myoglobin in urine and increased serum creatine kinase (indicating rhabdomyolysis), especially after exercise. Muscle biopsy shows stored glycogen and decreased muscle phosphorylase activity. Specialized centers may be able to show abnormal muscle metabolism using an MRI machine in a test called spectroscopy. The ischemic forearm test (brief application of a tourniquet to cut off blood supply to the forearm, and then blood lactate is measured) can be helpful in making the diagnosis. In certain cases, genetic testing may be recommended. |
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