Mendelian randomization identifies OX40 as a potential mediator of the effects of cigarette smoking on palmoplantar pustulosis

We used two-step Mendelian randomization to investigate the inflammatory mediators underlying the effects of cigarette smoking on palmoplantar pustulosis (PPP). We first examined the causal effects of smoking on plasma cytokine levels and then those of smoking-associated cytokines on PPP risk. We identified OX40 as potential mediator of the effects of smoking on PPP.