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). This evidence concerns the gene PIGO and Elevated circulating alkaline phosphatase concentration.