PIGO deficiency: Palmoplantar keratoderma and novel mutations

Background: Several genetic defects have been identified in the glycosylphosphatidylinositol (GPI) anchor synthesis, including mutations in PIGO encoding phosphatidylinositol glycan anchor biosynthesis class O protein. These defects constitute a subgroup of the congenital disorders of glycosylation (CDG). Seven patients from five families have been reported carrying variants in PIGO that cause an autosomal recessive syndrome characterised by dysmorphism, psychomotor disability, epilepsy and hyperphosphatasemia. Methods: Whole exome sequencing was performed in a boy with dysmorphism, psychomotor disability, epilepsy, palmoplantar keratoderma, hyperphosphatasemia and platelet dysfunction without a clinical bleeding phenotype. Results: Two novel variants in PIGO were detected. The missense variant encoding p. His871Pro was inherited from the boy's father while the frameshift variant encoding p. Arg604ProfsTer40 was maternally inherited. Conclusion: A boy with two novel PIGO variants is reported. The skin phenotype and platelet dysfunction in this patient have not been described in previously reported patients with PIGO deficiency but it is of course uncertain whether these are caused by this disorder. The literature on PIGO deficiency is reviewed.