An ALG12-CDG patient with a novel homozygous intronic mutation associated with low ALG12 mRNA

Type I Congenital Disorders of Glycosylation (CDG-I) are inherited diseases presenting deficits in protein N-glycosylation involving either the biosynthesis of the lipid-linked oligosaccharide Glc₃Man₉GlcNAc₂-PP-dolichol or transfer of its oligosaccharide to protein. […] This is the first description of a pathogenic intronic ALG12 variant upstream of the first coding exon. The modification of the splicing process between intron 1 and exon 2, the very low transcript level and the absence of other mutations in the patient’s ALG12 gene lead us to conclude that this ALG12 variant is a predicted Loss of Function (pLOF) variant.