To date, mutations in six genes (PIGV, PIGY, PIGO, PGAP2, PIGW, and PGAP3) have been shown to cause hyperphosphatasia with mental retardation syndrome (HPMRS) in an autosomal recessive mode of inheritance (no autosomal dominant mutations have been reported thus far). The gene discussed is PGAP3; the disease is Elevated circulating alkaline phosphatase concentration.