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Genetics Home Reference: your guide to understanding genetic conditions     A service of the U.S. National Library of Medicine®


Reviewed January 2008

What is the official name of the FAH gene?

The official name of this gene is “fumarylacetoacetate hydrolase (fumarylacetoacetase).”

FAH is the gene's official symbol. The FAH gene is also known by other names, listed below.

What is the normal function of the FAH gene?

The FAH gene provides instructions for making an enzyme called fumarylacetoacetate hydrolase. This enzyme is abundant in the liver and kidneys, and smaller amounts are found in many tissues throughout the body. Fumarylacetoacetate hydrolase is the last in a series of five enzymes needed to break down the amino acid tyrosine, a protein building block found in many foods. Specifically, fumarylacetoacetate hydrolase converts a tyrosine byproduct called fumarylacetoacetate into smaller molecules that are either excreted by the kidneys or used in reactions that produce energy.

How are changes in the FAH gene related to health conditions?

tyrosinemia - caused by mutations in the FAH gene

Researchers have identified more than 40 FAH mutations that cause type I tyrosinemia. The altered FAH gene produces an unstable or inactive enzyme, which results in reduced or absent fumarylacetoacetate hydrolase activity. The most common FAH mutation disrupts how genetic information is spliced together to make the blueprint for producing fumarylacetoacetate hydrolase. This particular mutation, called a splice-site mutation, is written as IVS12 + 5G>A. Without sufficient fumarylacetoacetate hydrolase activity, tyrosine is not processed completely. Instead of being converted to harmless molecules, fumarylacetoacetate, a tyrosine byproduct, accumulates in the liver and kidneys. Elevated levels of fumarylacetoacetate are thought to be toxic and to cause the liver and kidney problems characteristic of type I tyrosinemia. Individuals with this disorder are also at risk of liver cancer (hepatocarcinoma). Research studies suggest that elevated levels of fumarylacetoacetate in liver cells initiate or promote tumor development.

In several cases of type I tyrosinemia, the FAH gene mutation has been observed to revert to the normal state in some liver cells. If enough cells have the reverted gene, some fumarylacetoacetate hydrolase activity is restored. Researchers have found a correlation between the severity of symptoms and the extent of reversion in liver cells. People with severe symptoms of type I tyrosinemia have few reverted cells, while those with milder symptoms have many cells with the reverted FAH gene.

Where is the FAH gene located?

Cytogenetic Location: 15q25.1

Molecular Location on chromosome 15: base pairs 80,152,890 to 80,186,581

The FAH gene is located on the long (q) arm of chromosome 15 at position 25.1.

The FAH gene is located on the long (q) arm of chromosome 15 at position 25.1.

More precisely, the FAH gene is located from base pair 80,152,890 to base pair 80,186,581 on chromosome 15.

See How do geneticists indicate the location of a gene? ( in the Handbook.

Where can I find additional information about FAH?

You and your healthcare professional may find the following resources about FAH helpful.

You may also be interested in these resources, which are designed for genetics professionals and researchers.

What other names do people use for the FAH gene or gene products?

  • beta-Diketonase
  • FAA
  • fumarylacetoacetase

See How are genetic conditions and genes named? ( in the Handbook.

What glossary definitions help with understanding FAH?

amino acid ; cancer ; enzyme ; gene ; hepatocarcinoma ; hydrolase ; kidney ; liver cancer ; mutation ; protein ; reversion ; splice-site mutation ; toxic ; tumor ; tyrosine

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.


  • Arranz JA, Piñol F, Kozak L, Pérez-Cerdá C, Cormand B, Ugarte M, Riudor E. Splicing mutations, mainly IVS6-1(G>T), account for 70% of fumarylacetoacetate hydrolase (FAH) gene alterations, including 7 novel mutations, in a survey of 29 tyrosinemia type I patients. Hum Mutat. 2002 Sep;20(3):180-8. (
  • Bergeron A, D'Astous M, Timm DE, Tanguay RM. Structural and functional analysis of missense mutations in fumarylacetoacetate hydrolase, the gene deficient in hereditary tyrosinemia type 1. J Biol Chem. 2001 May 4;276(18):15225-31. Epub 2001 Jan 22. (
  • Demers SI, Russo P, Lettre F, Tanguay RM. Frequent mutation reversion inversely correlates with clinical severity in a genetic liver disease, hereditary tyrosinemia. Hum Pathol. 2003 Dec;34(12):1313-20. (
  • NCBI Gene (
  • St-Louis M, Tanguay RM. Mutations in the fumarylacetoacetate hydrolase gene causing hereditary tyrosinemia type I: overview. Hum Mutat. 1997;9(4):291-9. Review. (


The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? ( in the Handbook.

Reviewed: January 2008
Published: July 27, 2015