Homozygous or compound heterozygous ENPP1 mutations have been previously described to lead not only to generalized arterial calcification of infancy (GACI1) (30, 31, 32), but also to autosomal-recessive hypophosphatemic rickets type 2 (ARHR2) in rare cases (8). Here, ENPP1 is linked to hypophosphatemic rickets, autosomal recessive, 2.