Reflections and Mendelian randomization analysis of patients with vitiligo and pancreatic cancer

Objectives: A special case of vitiligo patient with advanced pancreatic cancer was observed in our clinical practice, which prompted us to think about whether there is an association between the two diseases, and to further investigate whether there is a causal relationship between the two diseases, a two-sample Mendelian randomization analysis was performed. Methods: In this study, two-sample Mendelian randomization (MR) analyses were performed using inverse variance weighted (IVW), weighted median, MR-Egger regression, Simple mode and Weighted mode. We used the publicly available Genome-wide association study (GWAS) summary statistics set on vitiligo of European origin (n=333064; Neale Lab) as the exposed GWAS; Samples of pancreatic cancer from the East Asian Biobank (total = 196187; cases = 442, controls = 195745; Neale Lab) were used as outcome. Results: We screened 19 single nucleotide polymorphisms (SNPs) with genome-wide significance from GWASs on vitiligo as instrumental variables (P < 5.00E-06; linkage disequilibrium r2 < 0.1). Analysis of the results using various methods such as IVW, MR-Egger regression, Weighted median, Simple mode and Weighted mode did not support the existence of a causal relationship between vitiligo and pancreatic cancer (P > 0.05). Cochran's Q test and funnel plot showed no evidence of heterogeneity and asymmetry. And the intercept of MR-Egger analysis result = 0.017400347494319, P = 0.666 further suggests that there is no directional multiplicity of results. Conclusion: The results of the MR analysis do not support a causal relationship between vitiligo and an increased risk of pancreatic cancer.