1. NANS-CDG:Delineation of the Genetic, Biochemical, and Clinical Spectrum
- Author
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den Hollander, Bibiche, Rasing, Anne, Post, Merel A., Klein, Willemijn M., Oud, Machteld M., Brands, Marion M., de Boer, Lonneke, Engelke, Udo F.H., van Essen, Peter, Fuchs, Sabine A., Haaxma, Charlotte A., Jensson, Brynjar O., Kluijtmans, Leo A.J., Lengyel, Anna, Lichtenbelt, Klaske D., Østergaard, Elsebet, Peters, Gera, Salvarinova, Ramona, Simon, Marleen E.H., Stefansson, Kari, Thorarensen, Ólafur, Ulmen, Ulrike, Coene, Karlien L.M., Willemsen, Michèl A., Lefeber, Dirk J., Karnebeek, Clara D.M.van, den Hollander, Bibiche, Rasing, Anne, Post, Merel A., Klein, Willemijn M., Oud, Machteld M., Brands, Marion M., de Boer, Lonneke, Engelke, Udo F.H., van Essen, Peter, Fuchs, Sabine A., Haaxma, Charlotte A., Jensson, Brynjar O., Kluijtmans, Leo A.J., Lengyel, Anna, Lichtenbelt, Klaske D., Østergaard, Elsebet, Peters, Gera, Salvarinova, Ramona, Simon, Marleen E.H., Stefansson, Kari, Thorarensen, Ólafur, Ulmen, Ulrike, Coene, Karlien L.M., Willemsen, Michèl A., Lefeber, Dirk J., and Karnebeek, Clara D.M.van
- Abstract
Background: NANS-CDG is a recently described congenital disorder of glycosylation caused by biallelic genetic variants in NANS, encoding an essential enzyme in de novo sialic acid synthesis. Sialic acid at the end of glycoconjugates plays a key role in biological processes such as brain and skeletal development. Here, we present an observational cohort study to delineate the genetic, biochemical, and clinical phenotype and assess possible correlations. Methods: Medical and laboratory records were reviewed with retrospective extraction and analysis of genetic, biochemical, and clinical data (2016–2020). Results: Nine NANS-CDG patients (nine families, six countries) referred to the Radboudumc CDG Center of Expertise were included. Phenotyping confirmed the hallmark features including intellectual developmental disorder (IDD) (n = 9/9; 100%), facial dysmorphisms (n = 9/9; 100%), neurologic impairment (n = 9/9; 100%), short stature (n = 8/9; 89%), skeletal dysplasia (n = 8/9; 89%), and short limbs (n = 8/9; 89%). Newly identified features include ophthalmological abnormalities (n = 6/9; 67%), an abnormal septum pellucidum (n = 6/9; 67%), (progressive) cerebral atrophy and ventricular dilatation (n = 5/9; 56%), gastrointestinal dysfunction (n = 5/9; 56%), thrombocytopenia (n = 5/9; 56%), and hypo–low-density lipoprotein cholesterol (n = 4/9; 44%). Biochemically, elevated urinary excretion of N-acetylmannosamine (ManNAc) is pathognomonic, the concentrations of which show a significant correlation with clinical severity. Genotypically, eight novel NANS variants were identified. Three severely affected patients harbored identical compound heterozygous pathogenic variants, one of whom was initiated on experimental prenatal and postnatal treatment with oral sialic acid. This patient showed markedly better psychomotor development than the other two genotypically identical males. Conclusions: ManNAc screening should be considered in all patients with IDD, short stature with
- Published
- 2021