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PYGM gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

PYGM gene

The PYGM gene provides instructions for creating the enzyme myophosphorylase, which is critical for breaking down glycogen into energy within muscle cells.

Normal Function

The PYGM gene provides instructions for making an enzyme called myophosphorylase. This enzyme is one of three related enzymes called glycogen phosphorylases that break down a complex sugar called glycogen in cells. Myophosphorylase is found only in muscle cells, where it breaks down glycogen into a simpler sugar called glucose-1-phosphate, which is then converted into glucose for energy.

Health Conditions Related to Genetic Changes

Glycogen storage disease type V

Approximately 130 mutations in the PYGM gene have been found to cause glycogen storage disease type V (GSDV). A shortage or dysfunction of the myophosphorylase enzyme impairs the normal breakdown of glycogen. As a result, muscle cells cannot produce enough energy, leading to the major features of GSDV, such as easily fatigued muscles.

Other Names for This Gene

  • glycogen phosphorylase, muscle form
  • myophosphorylase
  • phosphorylase, glycogen, muscle
  • PYGM_HUMAN

Frequently Asked Questions

re there any specific lifestyle or dietary recommendations for managing Glycogen Storage Disease Type V (GSDV)?::Management often focuses on avoiding strenuous exercise that triggers symptoms and adopting a diet that provides alternative energy sources. Some individuals benefit from a high-protein diet or consuming small, frequent carbohydrate-rich meals to maintain blood glucose levels. It's crucial to work with a healthcare team, including a dietitian, to develop a personalized management plan.
How is Glycogen Storage Disease Type V (GSDV) typically diagnosed?::Diagnosis of GSDV usually involves a combination of clinical evaluation, blood tests to check for elevated muscle enzymes, and a muscle biopsy to look for glycogen accumulation and measure myophosphorylase activity. Genetic testing for mutations in the PYGM gene can confirm the diagnosis.
If I have GSDV, what is the likelihood my children will inherit the condition?::Glycogen Storage Disease Type V (GSDV) is inherited in an autosomal recessive pattern. This means both parents must carry a copy of the mutated PYGM gene for a child to inherit the condition. If both parents are carriers, there is a 25% chance with each pregnancy that the child will have GSDV, a 50% chance they will be a carrier, and a 25% chance they will neither have the condition nor be a carrier. Genetic counseling can provide a more precise risk assessment for your family.
What are the common symptoms or early signs of Glycogen Storage Disease Type V (GSDV) that I should watch for?::GSDV primarily affects muscles. Common early signs include muscle pain, stiffness, and cramps, especially after exercise. You might also notice easy fatigability, meaning your muscles tire quickly with activity, and sometimes dark-colored urine (myoglobinuria) due to muscle breakdown.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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