ENPP1 and Pseudoxanthoma elasticum: Main protagonists are the osteoinductive Transforming Growth Factor beta (TGFβ) family (TGFβ1-3 and Bone Morphogenetic Proteins [BMP]), together with ectonucleotides (ENPP1), Wnt signalling and a variety of local and systemic calcification inhibitors, many of which have been previously associated with PXE, such as matrix Gla protein (MGP), osteocalcin (OC), bone sialoprotein (BSP or osteopontin), osteoprotegerin (OPG) and fetuin-A [3-9].