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Your GSD9 coordinator is
Dan Machin


GSD9 is now recognised as one of the more prevalent forms of GSD, accounting for 25% of all people affected by GSD.

There are four variants, sometimes known as 9a, 9b, 9c and 9d, but now going by the names of:
• PHKA2 (formerly 9a). This is carried on the X part of the gene and is normally seen in males, however some female carriers are affected. Some 75% of people with GSD9 have this liver variant.
• PHKB (formerly 9b). Only 20 people have been reported to have this variant which affects the liver and muscles.
• PHKG2 (formerly 9c). This is a recessive variant of GSD9 with liver and muscle symptoms.
• PHKG1 (formerly 9d and PHKA1). This variant primarily affects the muscles.

Main signs of most GSD9 variants (sub-types)

  • An enlarged liver (hepatomegaly) due to increased glycogen storage.
  • Hypoglycaemia (problems with maintaining blood sugar).

Muscle problems are present in some variants. A major feature is the wide variety of symptoms from person to person.

The information for this webpage came from the following paper. It does not cover the PHKG1 (formerly PHKA1 and GSD9d) muscle variant.

View the paper on GSD6 and GSD9.

Muscle type PHKG1 (GSD9d)

For this variant, please see the panel in the diagnosis and follow up section.


Other names

Glycogen phosphorylase b kinase deficiency

Affected Liver and muscle forms

X-linked and autosomal recessive patterns

Incidence Approx. 1 in 100,000
UK diagnosed About 150  (UK diagnosed explained)

Hypoglycaemia, hepatomegaly and muscle problems

Secondary symptoms

Secondary symptoms are varied but might include growth retardation, sleep difficulties with overnight irritability, ketosis and hyperlipidaemia


Symptoms are managed


Generally good but further studies are needed


How can we help?


Diagnosis & Follow up

Diagnosis, Parents’ guide, Diagnosis and Management guidelines


Information & Support

Coordinator, Social media, GSD & Me web site, Links


Activity & Exercise

Nothing available in this section yet

Research & Development

About clinical trials

Read some personal stories

Do you have an interesting personal story to tell? Just message us or visit the Notes for contributors.