Glycogen phosphorylase V, McArdle's Disease). More than 65 mutations in the PYGM gene that lead to McArdle disease have been identified to date. Symptoms of McArdle disease include muscle weakness, myalgia, and lack of endurance, all stemming from low glucose levels in muscle tissue. Mutations in the liver isoform of glycogen phosphorylase (PYGL) are associated with Hers' Disease (glycogen storage disease type VI). Hers' disease is often associated with mild symptoms normally limited to hypoglycemia, and is sometimes difficult to diagnose due to residual enzyme activity. The brain isoform of glycogen phosphorylase (PYGB) has been proposed as a biomarker for gastric cancer.
Glycogen storage disease type 0 of asymptomatic and oligosymptomatic siblings in several glycogen-storage disease type 0 families has suggested that glycogen-storage disease type 0 is underdiagnosed. The major morbidity is a risk of fasting hypoglycemia, which can vary in severity and frequency. Major long-term concerns include growth delay, osteopenia, and neurologic damage resulting in developmental delay, intellectual deficits, and personality changes. No sexual predilection is observed because the deficiency of glycogen synthetase activity is inherited as an autosomal recessive trait. Glycogen-storage disease type 0 is most commonly diagnosed during infancy and early childhood. Glycogen storage disease type 0 Glycogen storage disease type 0 is a