The three forms of autosomal recessive hypophosphatemic rickets (ARHR) result from mutations in DMP1 [ARHR1, [52]], ENPP1 [ARHR2, [26]], and FAM20C [ARHR3, [25]], while hypophosphatemic rickets and hyperparathyroidism (HRHPT) is caused by mutations that upregulate KLOTHO expression [53]. The gene discussed is ENPP1; the disease is hypophosphatemic rickets.