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

FTCD gene

The FTCD gene encodes a bifunctional enzyme responsible for the final two steps in the breakdown of the amino acid histidine.

Normal Function

The FTCD gene provides instructions for making an enzyme called formimidoyltransferase-cyclodeaminase. This enzyme is found mainly in the liver, although small amounts are found in the kidneys and the testes. Formimidoyltransferase-cyclodeaminase is called a bifunctional enzyme because it performs two functions.

The first function of formimidoyltransferase-cyclodeaminase is to act as a transferase, which is an enzyme that moves (transfers) a group of atoms from one molecule to another. By doing this, the enzyme converts formiminoglutamate (FIGLU) to 5-formiminotetrahydrofolate. The amino acid glutamate, which is a building block of many proteins, is also produced during this process.

Formimidoyltransferase-cyclodeaminase also acts as a deaminase, which is an enzyme that removes a group of nitrogen and hydrogen atoms from other molecules. By doing this, the enzyme converts 5-formiminotetrahydrofolate to a different tetrahydrofolate molecule. Tetrahydrofolate molecules are involved in producing purines and pyrimidines, which are the building blocks of DNA and its chemical cousin, RNA. The tetrahydrofolates carry small molecules called one-carbon units that are needed to produce these larger molecules.

These two functions make up the final two steps in the breakdown of the amino acid histidine.

Health Conditions Related to Genetic Changes

Glutamate formiminotransferase deficiency

Variants (also called mutations) in the FTCD gene cause glutamate formiminotransferase deficiency, an inherited disorder that can result in high levels of FIGLU in the urine. In the past, researchers recognized a mild form and a severe form of this condition. However, some people with glutamate formiminotransferase deficiency do not appear to have any related health problems.

The FTCD gene variants that cause glutamate formiminotransferase deficiency alter the function of formimidoyltransferase-cyclodeaminase, which disrupts the enzyme’s ability to completely break down histidine. If the enzyme’s transferase activity is impaired, FIGLU can build up in the body and then be released in the urine. It is unclear exactly how these changes are related to the specific health problems seen in some people with glutamate formiminotransferase deficiency.

Other Names for This Gene

  • formiminotransferase cyclodeaminase
  • LCHC1

Genomic Location

The FTCD gene is found on chromosome 21.

Frequently Asked Questions

Patients may present with developmental delay, growth failure, or unexplained anemia, but many are asymptomatic. The classic laboratory clue is a markedly elevated level of formiminoglutamate (FIGLU) in the urine after a histidine load test. Routine metabolic panels that show elevated FIGLU or unexplained folate‑dependent abnormalities (e.g., low methionine) often trigger targeted FTCD sequencing.
Because the enzyme participates in histidine catabolism and one‑carbon metabolism, a low‑histidine diet can reduce FIGLU accumulation, though strict restriction is rarely needed. More importantly, supplementation with folate (5‑methyltetrahydrofolate) and vitamin B12 supports the downstream folate cycle and may improve biochemical parameters. In severe cases, betaine or methionine supplementation has been used to bypass the metabolic block, but these interventions should be guided by a metabolic specialist.
The mild form often remains clinically silent; affected individuals live normal lives with only a biochemical abnormality. The severe form can present with growth retardation, intellectual disability, and hematologic abnormalities (macrocytic anemia). With early detection, appropriate nutritional therapy and regular monitoring of growth and neurodevelopment can improve outcomes. Lifelong follow‑up is recommended to watch for potential complications such as folate deficiency or liver dysfunction, but most patients achieve a stable health status when managed proactively.
First, a quantitative urine FIGLU assay is performed, usually after a histidine challenge; a result >10 mmol/mol creatinine is considered abnormal. If FIGLU is elevated, the next step is molecular testing—either a multigene panel for inborn errors of metabolism that includes FTCD or single‑gene sequencing. Some laboratories also offer copy‑number analysis to detect deletions. Confirmatory diagnosis requires identifying pathogenic variants in both alleles (autosomal recessive inheritance).
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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