glycine N-methyltransferase deficiency
Findings
No curated finding names glycine N-methyltransferase deficiency yet. Everything below is reference data from Mondo, HPO and GenCC, not evidence about what affects it.
Definition
Glycine N-methyltransferase deficiency (GNMT deficiency) is a very rare condition characterized by persistent and isolated excess levels of methionine in the blood (hypermethioninemia). The only clinical abnormalities are mild increase of the liver size (hepatomegaly) and chronic elevation of the transaminase levels in the blood without liver disease. Methionine may also be increased in urine. However, because elevated levels of methionine in the blood itself is a risk factor for development of neurological signs and symptoms, people with GNMT deficiency can have neurological problems when methionine levelsare greater than 800μmol/L. GNMT deficiency is caused by mutations in the GNMT gene. Inheritance is autosomal recessive. Treatment is not needed in most cases.
Definition from the Mondo Disease Ontology (MONDO:0011698), read 2026-09-29. CC BY 4.0.
Genes
1 gene
Germline variants in the gene encoding each protein, as classified by GenCC submitters, each in their own words. Limited, disputed and refuted submissions are listed too.
- GNMTHGNC:4415
- Strong · Labcorp Genetics (formerly Invitae) · Autosomal recessive · 2019
- Strong · PanelApp Australia · Autosomal recessive · 2025
- Limited · Ambry Genetics · Autosomal recessive · 2023
- Limited · ClinGen · Autosomal recessive · 2026
- Limited · Labcorp Genetics (formerly Invitae) · Unknown · 2020
Where it sits
- A kind of
Other names
3 names
Resolves to: glycine N-methyltransferase deficiency
- Also called
- GNMT deficiencyhypermethioninemia due to glycine N-methyltransferase deficiencyhypermethioninemia due to GNMT deficiency