It has been reported that the inactivating mutations of the ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) gene can lead to Generalized Arterial Calcification of Infancy 1 (GACI1) (OMIM #208000) and Autosomal-Recessive Hypophosphatemic Rickets 2 (ARHR2) (OMIM # 613312) (2, 3). Here, ENPP1 is linked to autosomal recessive hypophosphatemic rickets.