Glycogen Storage Disease, Type IXb (PHKB)

Glycogen storage disease, type IXb is an autosomal recessive disorder caused by pathogenic variants in the gene PHKB. This glycogen storage disease is characterized by a deficiency in liver and muscle cells of phosphorylase kinase (PhK), which is needed for glycogen phosphorylase activation. Liver PhK deficiency is characterized by hepatomegaly, growth retardation, fasting ketosis, and hypoglycemia, while muscle PhK deficiency may present with exercise intolerance, myalgia, muscle cramps, myoglobinuria, and progressive muscle weakness. While this disorder manifests in childhood, the symptoms improve with age and adults are generally asymptomatic. The life expectancy for this disorder is normal.

For information about carrier frequency and residual risk, please see the residual risk table.

This gene is included on the following panel(s):