Notably, Mendelian randomization (MR) analysis in this study confirmed a significant negative association between IRAK3 expression and bladder cancer risk, and its expression level was positively correlated with M0 macrophage infiltration in the tumor microenvironment, suggesting that IRAK3 may regulate the bladder tumor immune microenvironment. The gene discussed is IRAK3; the disease is urinary bladder carcinoma.