ACMG Statements and Guidelines
These online statements and guidelines are definitive and may be cited using the digital object identifier (DOI). These recommendations are designed primarily as an educational resource for medical geneticists and other healthcare providers to help them provide quality medical genetics services; they should not be considered inclusive of all proper procedures and tests or exclusive of other procedures and tests that are reasonably directed to obtaining the same results. Please refer to the leading disclaimer in each document for more information.
- Glycogen storage disease (GSD) types VI and IX are rare diseases of variable clinical severity affecting primarily the liver. GSD VI is caused by deficient activity of hepatic glycogen phosphorylase, an enzyme encoded by the PYGL gene. GSD IX is caused by deficient activity of phosphorylase kinase (PhK), the enzyme subunits of which are encoded by various genes: ɑ (PHKA1, PHKA2), β (PHKB), ɣ (PHKG1, PHKG2), and δ (CALM1, CALM2, CALM3). Glycogen storage disease types VI and IX have a wide spectrum of clinical manifestations and often cannot be distinguished from each other, or from other liver GSDs, on clinical presentation alone.