Hypophosphatasia (HPP; OMIM# 146300, 241500, 241510) is a rare hereditary disorder caused by loss-of-function mutations in the ALPL gene (MIM*171760) that encodes the tissue-nonspecific isozyme of alkaline phosphatase (TNSALP; UniprotKB# P05186). The gene discussed is ALPL; the disease is hypophosphatasia.