ABCC6 and Pseudoxanthoma elasticum: Pseudoxanthoma elasticum has been associated to mutations in the ABCC6 gene, a member of the ABC family of membrane transporters (it encodes for the membrane transporter MRP6), that is mainly expressed in liver and kidney (Bergen et al., 2000; Le Saux et al., 2000; Ringpfeil et al., 2000), whereas its expression is surprisingly low in tissues specifically involved in the clinical manifestations of PXE.