ENPP1 and Hypercalciuria: HR includes several subtypes such as X-linked hypophosphatemic rickets [XLHR; Online Mendelian Inheritance in Man (OMIM) #307800], which accounts for more than 80% of HR; autosomal dominant hereditary hypophosphatemic rickets [OMIM #193100: fibroblast growth factor 23 (FGF23)], autosomal recessive hereditary hypophosphatemic rickets (ARHR) [OMIM #241520: ARHR1 (DMP1); OMIM #613312: ARHR2 (ENPP1); OMIM #611061: ARHR3 (FMA20C)], hereditary hypophosphatemic rickets with hypercalciuria (OMIM #241530), and Dent disease (2).