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URL of this page: https://medlineplus.gov/genetics/gene/hprt1/

HPRT1 gene

hypoxanthine phosphoribosyltransferase 1

Normal Function

The HPRT1 gene provides instructions for producing an enzyme called hypoxanthine-guanine phosphoribosyltransferase (HGprt). This enzyme allows cells to recycle purines, which are building blocks of DNA and its chemical cousin RNA. Making new purines (called de novo purine synthesis) uses a lot of energy. Recycling purines (called the purine salvage pathway) requires little energy and is more efficient. As such, it is easier for cells to recycle purines than to make new ones. Recycling purines ensures that cells have a plentiful supply of building blocks for the production of DNA and RNA.

Purines also play an important role in providing energy for cells and helping cells communicate. A ready supply of purines is critical during development.

Health Conditions Related to Genetic Changes

Lesch-Nyhan syndrome

Genetic changes that cause disease are called pathogenic variants. Hundreds of pathogenic variants in the HPRT1 gene cause Lesch-Nyhan syndrome. Lesch-Nyhan syndrome is a condition that is characterized by severe movement problems that interfere with motor development. Affected individuals have behavioral problems that include self-injury, such as biting and hitting.  People with Lesch-Nyhan syndrome also develop arthritis due to the overproduction of uric acid, which is made during the breakdown of purines. Lesch-Nyhan syndrome occurs almost exclusively in boys and men.

The pathogenic variants in the HPRT1 gene that cause Lesch-Nyhan syndrome can severely reduce the amount of functional HGprt enzymes in cells or prevent cells from making this enzyme at all. Specifically, Lesch-Nyhan syndrome occurs when there is less than 1.5 percent of normal HGprt enzyme activity. Without enough HGprt enzymes, purines are not recycled but are instead broken down. During this process, abnormally high levels of uric acid are produced.

People who have pathogenic variants in the HPRT1 gene that cause cells to produce HGprt with 2 percent or more enzyme activity are considered to have a different form of the condition called Lesch-Nyhan variant or partial HPRT1 deficiency. The signs and symptoms of Lesch-Nyhan variant are milder than those of Lesch-Nyhan syndrome. Affected individuals usually have high uric acid levels and they can have neurological problems, but they do not injure themselves. Because Lesch-Nyhan syndrome and Lesch-Nyhan variant are caused by pathogenic variants in the same gene, they are sometimes considered to be part of the same disease spectrum. The exact causes of the neurological and behavioral problems in people with Lesch-Nyhan syndrome and Lesch-Nyhan variant are unclear.

More About This Health Condition

Other Names for This Gene

  • HGPRT
  • HPRT
  • Hypoxanthine guanine phosphoribosyl transferase

Additional Information & Resources

Tests Listed in the Genetic Testing Registry

Scientific Articles on PubMed

Catalog of Genes and Diseases from OMIM

Gene and Variant Databases

References

  • Duan J, Nilsson L, Lambert B. Structural and functional analysis of mutations at the human hypoxanthine phosphoribosyl transferase (HPRT1) locus. Hum Mutat. 2004 Jun;23(6):599-611. doi: 10.1002/humu.20047. Citation on PubMed
  • Jinnah HA, De Gregorio L, Harris JC, Nyhan WL, O'Neill JP. The spectrum of inherited mutations causing HPRT deficiency: 75 new cases and a review of 196 previously reported cases. Mutat Res. 2000 Oct;463(3):309-26. doi: 10.1016/s1383-5742(00)00052-1. Citation on PubMed
  • Jinnah HA. HPRT1 Disorders. 2000 Sep 25 [updated 2020 Aug 6]. In: Adam MP, Bick S, Mirzaa GM, Pagon RA, Wallace SE, Amemiya A, editors. GeneReviews(R) [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2026. Available from http://www.ncbi.nlm.nih.gov/books/NBK1149/ Citation on PubMed
  • Mileti LN, Baleja JD. The Role of Purine Metabolism and Uric Acid in Postnatal Neurologic Development. Molecules. 2025 Feb 11;30(4):839. doi: 10.3390/molecules30040839. Citation on PubMed
  • Nanagiri A, Shabbir N. Lesch-Nyhan Syndrome. 2023 Apr 24. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2026 Jan-. Available from http://www.ncbi.nlm.nih.gov/books/NBK556079/ Citation on PubMed

The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.