Pseudoxanthoma Elasticum: Genetic Variations in Antioxidant Genes Are Risk Factors for Early Disease Onset

Background: Pseudoxanthoma elasticum (PXE) is a rare hereditary disorder characterized by progressive calcifi-cation and fragmentation of elastic fibers in connective tissues. PXE is caused by mutations in the ABCC6 gene, which encodes the membrane transporter multidrug resistance–associated protein 6. Chronic oxidative stress was recently suggested to play a crucial role in the pathogenesis of the disease. Our aim was to investigate the association of PXE with genetic variation in genes coding for antioxidant enzymes. Methods:We used restriction fragment length polymor-phism and allele-specific PCR analyses to evaluate the distribution of single-nucleotide polymorphisms in the genes encoding catalase (CAT), superoxide dismutase 2 (SOD2), and glutathione peroxidase 1 (GPX1) in DNA samples from 117 German PXE patients and 117 healthy age- and sex-matched control individuals. Results: The investigated genetic variants had previ-ously been shown to affect the activities of these anti-oxidant enzymes. We found a correlation between ge-notype and age of disease onset for polymorphisms in CAT (c.262C>T), SOD2 (c.47C>T), and GPX1 (c.593C>T). Furthermore, the age of disease onset was inversely correlated with the number of mutated alleles, indicating a cumulative effect on the time of disease onset [mean (SD) age of 40.9 (13.6) years, 32.4 (16.3) years, and 25.7 (15.9) years for carriers of 0, 1–2, and>2 mutated alleles, respectively; P 0.03]. Conclusion: Our findings demonstrate that increased oxidative stress due to activity-affecting polymorphisms in genes encoding antioxidant enzymes leads to earlier PXE onset