Glycogen storage disease type 6- due to phosphorylation
Overview
Glycogen storage disease type VI, due to phosphorylation (medical condition): A rare, generally mild form of inherited glycogen storage disease where a deficiency of phosphorylase b kinase leads to hypoglycemia and accumulation of glycogen in the liver.
Symptoms
Some of the symptoms of Glycogen storage disease type VI, due to phosphorylation incude: * Enlarged liver * Ketosis * Low blood sugar * Growth retardation * Faintness
Causes
GSD VI results from a deficiency in the activity of one of several enzymes in the phosphorylase-activating cascade. Most cases result from defects of phosphorylase b kinase, an enzyme that activates phosphorylase by phosphorylation. Phosphorylase b kinase is a multimeric unit consisting of 4 different subunits, each coded by a unique gene located on different chromosomes. Mutations in 3 genes (PHKA2, PHKB, and PHKG2) have been demonstrated in patients with phosphorylase b kinase deficiency.2 In addition, several subtypes of phosphorylase kinase deficiency have been identified, based on the tissues affected and the mode of inheritance (autosomal recessive or X-linked recessive).3 The most common subgroup is the X-linked recessive form. Classic GSD VI results from a primary deficiency of liver phosphorylase (PYGL). Patients with a defect of the cAMP-dependent protein kinase have been infrequently reported.