Supplementary Material for: DNA Repair Gene Polymorphisms as Genetic Factors Associated with Presence of Seborrheic Keratoses

Introduction
Seborrheic keratoses (SK) are common benign epidermal tumors. Their pathogenesis is unknown, and no pathological significance is ascribed to them, although they could be part of paraneoplastic syndromes, in addition to presenting a variety of somatic mutations. SKs are associated with increased age, family history and sun-exposure.
Methods
This study aimed to analyze if SK was related to DNA repair genes polymorphisms and analyze if any epidemiological, clinical or environmental characteristics could modify their prevalence.
It was conducted an epidemiological, analytical, observational, cross-sectional, retrospective case-control study. Both univariate and multivariate logistic regression models were used to evaluate which characteristics were associated with having >50 SKs versus <10.
Results
A total of 294 patients with melanoma were studied, 270 (91.8%) having had less than 10 SKs, while 24 (8.2%) >50. Of all the polymorphisms studied, only rs25487 in XRCC1 reached statistical significance (OR=3.56; 95% CI 1.36-9.33; p=0.01). In addition, an increasing age (OR=1.07; 95% CI 1.03-1.11; p=0.001) and the phototype (III-V vs. I-II) (OR=0.28; 95% CI 0.12-0.68; P=0.005) were related to the presence of >50 SKs.
Conclusion
We identified that increasing age, having a phototype I-II and the existence of the rs25487 polymorphism could be associated with the occurrence of KS.