has material basis in germline mutation in GNMT disorder of methionine catabolism glycine N-methyltransferase deficiency https://rarediseases.info.nih.gov/diseases/10764/glycine-n-methyltransferase-deficiency https://www.malacards.org/card/glycine_n_methyltransferase_deficiency DOID:0111037 icd11.foundation:16192453 SCTID:763720007 Glycine N-methyltransferase deficiency GNMT deficiency hypermethioninemia due to GNMT deficiency OMIM:606664 UMLS:C1847720 MEDGEN:338300 MONDO:0011698 hypermethioninemia due to glycine N-methyltransferase deficiency glycine N-methyltransferase deficiency 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. GARD:0010764 Orphanet:289891