ABCG2 and Pseudoxanthoma elasticum: In this study, we have examined the expression profile of selected ABC transporter genes associated with cholesterol homeostasis [9–11] in Abcc6−/− mice compared to wild type (WT) mice, because there are several indications that PXE is linked to an alteration of cholesterol metabolism accompanied by altered ABC transporter gene expression [8, 12, 13].