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

CYBA gene

The CYBA gene provides instructions for creating a critical component of the NADPH oxidase enzyme complex, which is essential for the immune system's ability to destroy foreign invaders.

Normal Function

The CYBA gene provides instructions for making a protein called the cytochrome b-245 alpha chain (also known as p22-phox). This protein is a subunit of an enzyme complex called NADPH oxidase, which plays an essential role in the immune system. Within this complex, the cytochrome b-245 alpha chain functions alongside a beta chain partner (produced from the CYBB gene). Both chains are required for the complex to function properly.

NADPH oxidase is primarily active in immune system cells called phagocytes, which catch and destroy foreign invaders such as bacteria and fungi. This enzyme also helps regulate the activity of neutrophils, which adjust the inflammatory response to optimize healing. When phagocytes encounter foreign invaders, they trigger the assembly of NADPH oxidase, which converts oxygen into toxic reactive oxygen species, such as hydrogen peroxide and hypochlorous acid, to eliminate the threat.

Health Conditions Related to Genetic Changes

Chronic granulomatous disease

More than 40 mutations in the CYBA gene have been identified as a cause of chronic granulomatous disease. This condition results in a weakened immune system, leaving individuals at an increased risk for recurrent infections and inflammation.

  • Mutations in the CYBA gene account for less than 5 percent of all cases of this condition.
  • These mutations often change single amino acids or cause the protein to be abnormally short and nonfunctional.
  • An altered alpha chain prevents the proper assembly or function of the NADPH oxidase complex, even if the beta chain is present.
  • Without functional NADPH oxidase, phagocytes cannot produce the reactive oxygen species necessary to kill bacteria and fungi, and neutrophil activity remains unregulated.

Other Names for This Gene

  • CY24A_HUMAN
  • cytochrome b light chain
  • cytochrome b(558) alpha chain
  • cytochrome b, alpha polypeptide
  • cytochrome b-245 light chain
  • cytochrome b-245, alpha polypeptide
  • cytochrome b558 subunit alpha
  • flavocytochrome b-558 alpha polypeptide
  • neutrophil cytochrome b 22 kDa polypeptide
  • p22phox
  • superoxide-generating NADPH oxidase light chain subunit

Frequently Asked Questions

Prophylactic antibiotics (e.g., trimethoprim‑sulfamethoxazole) and antifungal agents (e.g., itraconazole) are standard. Vaccinations, especially against pneumococcus and Haemophilus influenzae type b, should be up to date. Avoid exposure to soil or dust that may contain Aspergillus spores, practice good hand hygiene, and maintain regular follow‑up with an immunology specialist.
Diagnosis usually starts with a functional oxidative burst test (e.g., dihydrorhodamine flow cytometry) to show defective neutrophil activity. If abnormal, targeted genetic sequencing of the CYBA gene confirms the mutation. No special preparation is needed beyond a routine blood draw, but avoid antibiotics for at least 48 hours if possible, as they can affect the functional assay.
CYBA mutations cause an autosomal recessive form of CGD. Both parents must carry one defective copy for a child to be affected (25 % risk). If you are a carrier, each pregnancy has a 50 % chance of producing a carrier child and a 25 % chance of an affected child.
People with CYBA‑CGD are prone to bacterial infections such as Staphylococcus aureus, Serratia marcescens, and Burkholderia cepacia, as well as fungal infections like Aspergillus species. Seek emergency care promptly if you develop high fever, rapid breathing, severe cough, painful swollen lymph nodes, or any signs of sepsis (e.g., confusion, low blood pressure).
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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