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glycine N-methyltransferase deficiency - Clinical Profile, Genes & Research | Kisho | Kisho

Rare Disease

glycine N-methyltransferase deficiency

MONDO:0011698

Also known as:GNMT deficiencyhypermethioninemia due to GNMT deficiencyhypermethioninemia due to glycine N-methyltransferase deficiency

Overview

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.

GeneticsAutosomal recessive · GNMT (chr 6)

Clinical Presentation

Built from Human Phenotype Ontology (HPO) phenotype annotations and GeneReviews clinical descriptions. Features represent findings documented across known cases — not an exhaustive list of possible symptoms.

Features include: Hypermethioninemia, Enlarged liver (hepatomegaly), and Elevated circulating hepatic transaminase concentration.

Organ System	Phenotype Count	Example Features
Digestive system	2	Enlarged liver (hepatomegaly), Elevated circulating hepatic transaminase concentration

Genetic Landscape

Assembled from HGNC gene records, ClinGen gene-disease validity evidence, and ClinVar pathogenic variant data. Validity classifications reflect the strength of published evidence linking each gene to this disease.

GNMT encodes glycine N-methyltransferase (295 aa). Catalyzes the methylation of glycine by using S-adenosylmethionine (AdoMet) to form N-methylglycine (sarcosine) with the concomitant production of S-adenosylhomocysteine (AdoHcy), a reaction regulated by the binding of 5-methyltetrahydrofolate. Highest expression in Pancreas (270.4 TPM) and Liver (124.8 TPM).

Glycine N-methyltransferase deficiency has limited evidence linking it to mutations in the GNMT gene on chromosome 6.

The GNMT protein participates in GNMT tetramer transfers methyl group from AdoMet to Gly to form AdoHyc and SARC, AdoSeMet is converted to AdeSeHCys by MetTrans(1), and Pancreatic pro-acinar cell produces pancreatic acinar cell pathways.

GNMT is classified as a druggable target (Enzyme category) with score 7.0.

Diagnosis

Genetic testing for GNMT is available. Testing is considered research-grade for diagnosis.

Biomarker and diagnostic research for glycine N-methyltransferase deficiency has been reported in the published literature.

Research Landscape

Sourced from ClinicalTrials.gov and PubMed. Publication types are classified using NLM-curated article metadata; research type breakdowns reflect the nature of published work for this disease.

No clinical trials have been registered for glycine N-methyltransferase deficiency.

10 publications have been identified in PubMed for glycine N-methyltransferase deficiency. Research spans Case Report / Case Series (30%), Basic Science / Preclinical (30%), and Review / Meta-Analysis (20%).

Research Type	Count	% of Total
Patient case studies	3	30%

Data assembled from 7 of 12 sources · Last updated Sep 20, 2026, 8:41 AM UTC

MONDOHPOClinicalTrials.govFDAPubMedHGNCClinVarClinGenGeneReviewsOrphanetOMIMRUSP

Medical References

External Resources

OMIM

Online Mendelian Inheritance in Man

OMIM:606664

Orphanet

European rare disease database

Orphanet:289891

GARD

Genetic and Rare Diseases Info Center

GARD:10764

Questions for Your Care Team

→Should my partner and I meet with a genetic counselor to discuss carrier status and family planning?
→Are there specialists or centers of excellence for this condition in my area?
→Is there a patient registry I should consider joining?

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glycine N-methyltransferase deficiency

Overview

Clinical Presentation

Genetic Landscape

Diagnosis

Research Landscape

Medical References

External Resources

OMIM

Orphanet

GARD

Questions for Your Care Team

Questions for Your Care Team

Explore clinical features

Recent Publications

glycine N-methyltransferase deficiency

Overview

Clinical Presentation

Genetic Landscape

Diagnosis

Research Landscape

Medical References

External Resources

OMIM

Orphanet

GARD

Related Diseases

Questions for Your Care Team

Questions for Your Care Team

Explore clinical features

Recent Publications