Mudd et al. (2001) reported 2 Italian sibs, a 4-year-old girl and her 9-year-old brother, with a novel form of persistent isolated hypermethioninemia without cystathionine beta-synthase deficiency (236200), tyrosinemia type I (276700), or liver disease. The children exhibited ... Mudd et al. (2001) reported 2 Italian sibs, a 4-year-old girl and her 9-year-old brother, with a novel form of persistent isolated hypermethioninemia without cystathionine beta-synthase deficiency (236200), tyrosinemia type I (276700), or liver disease. The children exhibited elevations of plasma S-adenosylmethionine, but plasma sarcosine was normal. These observations suggested deficiency of glycine N-methyltransferase activity. The only clinical abnormalities in these sibs were mild hepatomegaly and chronic elevation of serum transaminases not attributable to conventional causes of liver disease.
In the 2 Italian sibs with GNMT deficiency reported by Mudd et al. (2001), Luka et al. (2002) found compound heterozygosity for 2 missense mutations in the GNMT gene (606628.0001-606628.0002). These were the first reported cases of an ... In the 2 Italian sibs with GNMT deficiency reported by Mudd et al. (2001), Luka et al. (2002) found compound heterozygosity for 2 missense mutations in the GNMT gene (606628.0001-606628.0002). These were the first reported cases of an inborn error affecting the activity of GNMT.