Genetic mutations in the ALPL gene-encoding TNAP lead to hypophosphatasia (HPP; OMIM# 241500, 241510, and 146300) characterized by low circulating alkaline phosphatase (ALP), rickets in children and/or osteomalacia in adults, and with a very broad range of severity with several clinical types (from most to least severe: perinatal lethal, infantile, severe or mild childhood, adult, and odontohypophosphatasia) (12). The gene discussed is ALPL; the disease is hypophosphatasia.