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

PIGA gene

The PIGA gene provides instructions for creating a protein essential for anchoring other proteins to the cell membrane, a process critical for protecting blood cells.

Normal Function

The PIGA gene provides instructions for making a protein called phosphatidylinositol glycan class A (shortened to PIG-A). The PIG-A protein takes part in a series of steps that produce a molecule called a glycophosphatidylinositol (GPI) anchor. Specifically, the PIG-A protein is one piece of a group of proteins that performs the first step of the series, which produces an intermediate molecule called N-acetylglucosaminyl phosphatidylinositol, or GlcNAc-PI.

The GPI anchor, the ultimate product of the series of steps, attaches many different proteins to the cell membrane. These proteins are known as GPI-anchored proteins. Anchored proteins have a variety of roles, including sticking cells to one another, relaying signals into cells, and protecting cells from destruction.

Health Conditions Related to Genetic Changes

Paroxysmal nocturnal hemoglobinuria

Variants (also known as mutations) in the PIGA gene cause a condition called paroxysmal nocturnal hemoglobinuria (PNH). People with this condition have episodes of blood in the urine (hemoglobinuria) that results from the breakdown of red blood cells. A tendency to develop blood clots (thrombosis) and other blood-cell abnormalities also occur in this condition.

In people with PNH, variants of the PIGA gene occur during a person’s lifetime and are present only in certain cells. These changes, which are called somatic variants, are not inherited. For the condition to develop, one or more somatic PIGA gene variants occur in blood-forming cells called hematopoietic stem cells. As the abnormal hematopoietic stem cells multiply, populations of abnormal blood cells are formed. Two important GPI-anchored proteins normally found on the surface of red blood cells protect them from being broken down during immune reactions. Without these proteins, the abnormal red blood cells are prematurely destroyed.

Other disorders

Inherited (germline) variants in the PIGA gene can cause a disorder called PIGA deficiency, which refers to a spectrum of conditions with varied features and severity. Severely affected individuals typically have profound intellectual disability, seizures known as infantile spasms, weak muscle tone (hypotonia), distinctive facial features, and abnormalities of the brain and spinal cord. Less severely affected individuals have mild to moderate intellectual disability and infantile spasms.

Simpson-Golabi-Behmel syndrome

MedlinePlus Genetics provides information about Simpson-Golabi-Behmel syndrome.

Other Names for This Gene

  • GLCNAC-PI synthesis protein
  • GPI anchor biosynthesis
  • GPI3
  • phosphatidylinositol glycan anchor biosynthesis, class A
  • phosphatidylinositol glycan anchor biosynthesis, class A (paroxysmal nocturnal hemoglobinuria)
  • phosphatidylinositol glycan, class A (paroxysmal nocturnal hemoglobinuria)
  • phosphatidylinositol N-acetylglucosaminyltransferase subunit A
  • phosphatidylinositol-glycan biosynthesis, class A protein
  • PIG-A
  • PIGA_HUMAN

Frequently Asked Questions

Treatment for PNH focuses on managing symptoms and preventing complications, especially blood clots and severe anemia. Eculizumab and ravulizumab are targeted therapies that inhibit complement activation, a key mechanism in PNH, significantly reducing red blood cell destruction and the risk of thrombosis. Other management strategies include blood transfusions for anemia, anticoagulants to prevent clots, and iron and folic acid supplementation.
Early symptoms of PNH can be subtle and non-specific, making diagnosis challenging. Common signs include dark-colored urine, especially in the morning (due to hemoglobinuria), unexplained fatigue, shortness of breath, abdominal pain, difficulty swallowing, and a tendency to bruise easily. Some individuals may also experience recurrent blood clots (thrombosis) in unusual locations, which can be a serious complication.
Yes, that is correct. The PIGA gene variants that cause PNH are somatic, meaning they are acquired during a person's lifetime in blood-forming stem cells and are not present in the germline (sperm or egg cells). Therefore, PNH is not an inherited condition and cannot be passed down from an affected parent to their children.
PNH is primarily diagnosed through a specialized blood test called flow cytometry. This test detects the absence or reduced expression of specific GPI-anchored proteins (like CD55 and CD59) on the surface of red blood cells, white blood cells, and platelets. While the PIGA gene variant itself is not directly tested in routine diagnosis, the characteristic lack of GPI-anchored proteins is a direct consequence of the somatic PIGA mutation.
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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