GPI and Elevated circulating alkaline phosphatase concentration: The protein PGAP2 encoded by the gene PGAP2 influences the maturation of glycosylphosphatidylinositol (GPI) anchors on GPI-anchored proteins, and protein coding mutations of PGAP2 were suggested to lead to an autosomal recessive syndrome characterized as hyperphosphatasia and intellectual disability (Hansen et al., 2013).