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

XDH gene

The XDH gene provides instructions for making an enzyme essential for breaking down purines and is linked to the development of hereditary xanthinuria.

Normal Function

The XDH gene provides instructions for making an enzyme called xanthine dehydrogenase. This enzyme is involved in the normal breakdown of purines, which are building blocks of DNA and its chemical cousin, RNA. Specifically, it carries out the final two steps in the process: the conversion of a molecule called hypoxanthine to another molecule called xanthine, and the conversion of xanthine to uric acid, a waste product that is normally excreted in urine and feces.

Xanthine dehydrogenase has been studied extensively because it can be involved in the production of molecules called superoxide radicals. Specifically, xanthine dehydrogenase is sometimes converted to another form called xanthine oxidase, which produces superoxide radicals. These molecules are byproducts of normal cell processes, and they must be broken down regularly to avoid damaging cells. Superoxide radicals are thought to play a role in many diseases, including heart disease and high blood pressure (hypertension).

Researchers suspect that xanthine dehydrogenase plays a role in milk production (lactation) in women. However, the enzyme's role in lactation is unclear.

Health Conditions Related to Genetic Changes

Hereditary xanthinuria

At least 12 mutations in the XDH gene have been found to cause hereditary xanthinuria type I, a condition that most often affects the kidneys. These mutations reduce or eliminate the activity of xanthine dehydrogenase. As a result, the enzyme is not available to carry out the last two steps of purine breakdown. Because xanthine is not converted to uric acid, affected individuals have high levels of xanthine and very low levels of uric acid in their blood and urine.

The excess xanthine can accumulate in the kidneys and other tissues. In the kidneys, xanthine forms tiny crystals that occasionally build up to create kidney stones. These stones can impair kidney function and ultimately cause kidney failure. Less commonly, xanthine crystals build up in the muscles, causing pain and cramping. In some people with hereditary xanthinuria, the condition does not cause any health problems.

Other Names for This Gene

  • xanthine dehydrogenase/oxidase
  • xanthine oxidoreductase
  • XO
  • XOR

Frequently Asked Questions

Xanthine dehydrogenase can be converted into another enzyme form called xanthine oxidase. This enzyme is involved in the production of superoxide radicals, which are reactive oxygen species. While these radicals are normal byproducts of cell metabolism, excessive production can lead to oxidative stress. Researchers believe that this oxidative stress may contribute to the development of various diseases, including cardiovascular issues and hypertension, although the direct clinical impact in humans is still an area of ongoing study.
In individuals with hereditary xanthinuria type I, the enzyme xanthine dehydrogenase is non-functional or significantly reduced. This prevents the final step of purine breakdown, meaning xanthine is not converted into uric acid. Consequently, affected individuals have very low levels of uric acid in their blood and urine, while simultaneously having elevated levels of xanthine. This is the opposite of the typical pattern seen in gout or hyperuricemia.
Researchers have suspected that the xanthine dehydrogenase enzyme plays a role in lactation, or milk production, in women. However, the exact mechanism and the extent of its involvement remain unclear. Current scientific understanding does not provide definitive evidence linking XDH gene mutations to lactation disorders, and more research is needed to clarify this potential biological connection.
The most significant health risk for individuals with hereditary xanthinuria type I is the formation of kidney stones. Because the body cannot convert xanthine into uric acid, xanthine accumulates in the urine. Xanthine is poorly soluble, leading to the formation of crystals and stones in the kidneys. These stones can cause pain, urinary tract obstruction, and potential kidney damage if not managed properly.
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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