ABCC6 and pseudoxanthoma elasticum (inherited or acquired): ABCC6 is primarily expressed in the liver and kidneys while, remarkably, expression is low in tissues affected by PXE, such as the skin, vessel walls, and Bruch’s membrane of the eye, adding to the hypothesis that PXE is a metabolic disorder caused by a decrease in plasma and tissue concentrations of an ABCC6-transported or -related factor [24].