ALPL and hypophosphatasia: Hypomorphic ALPL mutation(s) cause hypophosphatasia (HPP) [4], a rare form of rickets or osteomalacia [5] featuring low serum alkaline phosphatase (ALP) activity and with an incidence for its most severe forms of 1:100,000 [6] and 1:300,000 [7] in the general population [6] of North America and Europe, respectively, but 1 per 2500 births in Canadian Mennonites [8].