McArdle disease (also known as glycogen storage disease type V) is a pure myopathy caused by an inherited deficit of myophosphorylase, the skeletal muscle isoform of the enzyme glycogen phosphorylase.
- Glycogen storage disease V·
- Autosomal recessive muscle disorder due to myophosphorylase deficiency·
- Prototype of muscle glycogenosis manifested by exercise intolerance.·
- In clinical setting, exercise related symptoms, including painful contractures, and, in about 50% of cases, rhabdomyolysis and myoglobinurea occur after brief strenuous isometric effort, or intense sustained dynamic exercise.·
- Symptoms relieved by rest.· Permanent weakness may occur.
Symptoms usually start later in life, affecting proximal greater than distal muscles