ENPP1 and Pseudoxanthoma elasticum: Generalized arterial calcification of infancy (GACI)—caused by mutations in the gene Ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1)—and pseudoxanthoma elasticum (PXE)—caused by mutations in the gene ATP binding cassette subfamily C member 6 (ABCC6)—are rare autosomal recessive genetic disorders associated with arterial and cartilage calcification, and ectopic calcifications of elastic fibers, respectively [41,42].