A case report of PGAP2-related hyperphosphatasia with impaired intellectual development syndrome in a Chinese family and literature review

Abstract

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Recently, mutations have been identified in six genes (PIGA, PIGY, PIGO, PGAP2, PIGW and PGAP3) encoding proteins in the Glycosyl phosphatidylinositol(GPI)-anchor-synthesis pathway in individuals with hyperphosphatasia with impaired intellectual development syndrome(HPMRS). Reports involving the rare pathogenic gene, post-GPI attachment to proteins 2 (PGAP2) are quite limited. In this study, we reported two patients with PGAP2 variants related neurodevelopmental disorders from Asian population. The proband, onset of epileptic spasms at 5 months, concurrently with global developmental dalay, facial malformation and elevated alkaline phosphatase. His younger sister, onset of epileptic spasms at 2 months, having similar clinical features as the proband. Their phenotypes are consistent with PGAP2 related diseases. The two missense variants [c.686C>T (p.Ala229Val) and c.677C>T (p.Thr226Ile)] in PGAP2 gene found in this family were segregation with the disease, while c.677C>T (p.Thr226Ile) was a novel variant. All the two patients showed a positive response to ACTH treatment and high-dose pyridoxine. In summary, this study contributes to expanding the pathogenic variant spectrum of PGAP2 related HPMRS, and provides new insights into the treatment.

Keywords

• PGAP2 variants
• hyperphosphatasia with impaired intellectual development syndrome
• epileptic spasms
• facial malformation
• ACTH treatment
• pyridoxine