Comment on Late-Onset Nonketotic Hyperglycinemia With a Heterozygous Novel Point Mutation of the GLDC Gene.

We read with interest the article by Brenton et al. 1 Brenton N.J. Rust R.S. Late-onset nonketotic hyperglycinemia with a hetetozygous novel point mutation of the GLDC gene. Pediatr Neurol. 2014; 50: 536-538 Abstract Full Text Full Text PDF PubMed Scopus (7) Google Scholar We would like to highlight a concern with the conclusion that a single heterozygous mutation in GLDC would be causative of an atypical form of nonketotic hyperglycinemia (NKH). The authors report a girl with attenuated NKH in which only a single heterozygous missense mutation in GLDC was reported upon sequencing. NKH is an autosomal recessive disease requiring biallelic mutations in GLDC or AMT to result in a clinical phenotype. 2 Coughlin II, C.R. Swanson M.A. Kronquist K. et al. The genetic basis of classic nonketotic hyperglycinemia due to mutations in GLDC and AMT. Genet Med. 2017; 19: 104-111 Crossref PubMed Scopus (40) Google Scholar In our experience, heterozygous parents and siblings of individuals affected with NKH have remained asymptomatic, and are not at risk for symptoms of NKH.