Uncovering the genetic basis of hyperphosphatasia with impaired intellectual development syndrome type 2: identification of a novel biallelic nonsense mutation in PIGO gene

Background: Glycosylphosphatidylinositol (GPI) is a glycolipid containing phosphatidylinositol related to the protein surfaces by covalent attachment. Inherited GPI deficiencies have various phenotypic chrematistics, which range from intellectual disability to dysmorphic features, epilepsy, and other severe anomalies. Methods: Molecular diagnosis was performed using whole exome sequencing (WES) followed by Sanger sequencing. Results: WES revealed a novel homozygous nonsense variant (c.250C>T; p.Gln84Ter) in the exon 2 of the phosphatidylinositol glycan anchor biosynthesis class Ogene that might explain the disease phenotype in the patient. Conclusion: This study will help in proper genetic counselling of the family and help in genotype-phenotype correlation in the future.