PHKA2
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Gene summaries condense public reference material; disease links and population data change as databases are updated. Clinical decisions belong with your care team.
phosphorylase kinase regulatory subunit alpha 2
Normal Function
Health Conditions Related to Genetic Changes
Glycogen storage disease type IX
At least 90 mutations in the PHKA2 gene are known to cause a form of glycogen storage disease type IX (GSD IX) called GSD IXa or X-linked liver glycogenosis (XLG). This is the most common form of GSD IX, accounting for approximately 75 percent of cases. GSD IXa affects liver function, and its characteristic features include an enlarged liver (hepatomegaly), slow growth, and periods of low blood glucose (hypoglycemia). These features usually improve over time. However, some affected individuals have a buildup of scar tissue (fibrosis) in the liver, which can rarely progress to irreversible liver disease (cirrhosis).
Mutations in the PHKA2 gene reduce the activity of phosphorylase b kinase in liver cells, although the mechanism is unknown. Reduction of this enzyme's function impairs glycogen breakdown. As a result, glycogen builds up in cells, and glucose is not available for energy. Glycogen accumulation in the liver leads to hepatomegaly and can damage the organ. The inability to break down glycogen for energy contributes to hypoglycemia and the other features of GSD IXa.
There are two subtypes of GSD IXa, known as XLG1 and XLG2, which are classified by the activity of phosphorylase b kinase in various tissues. In XLG1, the more common subtype, enzyme activity is decreased in the liver and in red blood cells. In contrast, in XLG2, the enzyme's activity appears low or normal in the liver and normal or high in red blood cells when measured by laboratory tests. The subtypes are indistinguishable based on symptoms.
More About This Health ConditionRelated Conditions
Glycogen storage disease type IX
Health Conditions Related to Genetic Changes
At least 90 mutations in the PHKA2 gene are known to cause a form of glycogen storage disease type IX (GSD IX) called GSD IXa or X-linked liver glycogenosis (XLG). This is the most common form of GSD IX, accounting for approximately 75 percent of cases. GSD IXa affects liver function, and its characteristic features include an enlarged liver (hepatomegaly), slow growth, and periods of low blood glucose (hypoglycemia). These features usually improve over time. However, some affected individuals have a buildup of scar tissue (fibrosis) in the liver, which can rarely progress to irreversible liver disease (cirrhosis).
Mutations in the PHKA2 gene reduce the activity of phosphorylase b kinase in liver cells, although the mechanism is unknown. Reduction of this enzyme's function impairs glycogen breakdown. As a result, glycogen builds up in cells, and glucose is not available for energy. Glycogen accumulation in the liver leads to hepatomegaly and can damage the organ. The inability to break down glycogen for energy contributes to hypoglycemia and the other features of GSD IXa.
There are two subtypes of GSD IXa, known as XLG1 and XLG2, which are classified by the activity of phosphorylase b kinase in various tissues. In XLG1, the more common subtype, enzyme activity is decreased in the liver and in red blood cells. In contrast, in XLG2, the enzyme's activity appears low or normal in the liver and normal or high in red blood cells when measured by laboratory tests. The subtypes are indistinguishable based on symptoms.