A Novel Homozygous ALG12 Mutation in a Patient with CDG Type Ig: New Report of a Case with a Mild Phenotype

Congenital disorders of glycosylation (CDG) are a group of rare genetic diseases caused by the deficiency of enzymes involved in the biosynthesis or remodeling of the glycan moieties of glycoconjugates. Most of CDG are autosomal recessive; however, few of them show autosomal dominant or X-linked inheritance. ALG12-CDG is an autosomal recessive inherited defect caused by a deficiency in the α-mannosyltransferase, dolichyl-P-mannose: Man7-GlcNAc-2-PP-dolichyl-alpha-6-mannosyltransferase (mannosyltransferase 8), which determines Man7GlcNAc2-PP-dolichol accumulation in tissues including fibroblasts. The clinical features of ALG12-CDG include dysmorphic features, developmental delay, hypotonia, progressive microcephaly, hypogammaglobulinemia, coagulopathies, and failure to thrive. Herein, we describe the case of a Sicilian patient with a milder phenotype bearing an ALG12 homozygous mutation. To date, including this patient, only 16 cases have been described with this form of CDG. Furthermore, our study contributes to understanding the milder ALG12-CDG cases and to further expanding the genotype-phenotype spectrum.