Characterization of Patients With Pseudoxanthoma Elasticum

Pseudoxanthoma elasticum (PXE) is a rare multisystem disorder of autosomal recessive inheritance (OMIM# 264800) and an estimated prevalence between 1:25.000 and 1:100.000. PXE is characterized by calcification and fragmentation of connective tissue rich in elastic fibers. Due to its high content of elastic fibers, Bruch Membrane in eyes of patients affected by PXE becomes thickened and calcified. The ocular phenotype is characterized by angioid streaks and peau d'orange but also choroidal neovascularizations and chorioretinal atrophy thereby in part mimicking the phenotype of age-related macular degeneration. The disease is due to mutations of the ABCC6-gene coding for a transmembrane protein which is mainly expressed in the liver and kidney. It is hypothesized that ABCC6 is involved in the excretion of a yet unknown factor from the liver which inhibits systemic calcification. In animal models several candidates for this factor have been identified but direct evidence for such a factor in patients with PXE is still missing. The primary purpose of this study is to further investigate the ocular phenotype of patients with PXE using multimodal imaging and functional testing to delineate the impact of Bruch membrane pathology on the eye. Furthermore, possible systemic anti-calcification factors, as well as associations with the vascular alterations are investigated to gain more insights into the pathogenesis of PXE..