For example, studies have highlighted the central role of pyrophosphate as a mineralization regulator, as germline mutations of the ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) gene, which encodes an enzyme mediating the generation of extracellular pyrophosphate, lead to idiopathic infantile arterial calcification [4], whilst germline mutations of the ANKH gene, which encodes a transmembrane protein involved in pyrophosphate transport, may lead to chondrocalcinosis [5]. Here, ENPP1 is linked to chondrocalcinosis.