Interestingly, the G/G-C/C, G/G-A/A as well as G/C-A/A of the c.-1493G > C – IDO1 (rs10089084) and c.804-7C > A – TPH1 (rs1799913) combined polymorphisms caused an increased frequency of stroke occurrence in the Polish population more than 20 times (p = 0.003), five times (p < 0.001), and nearly four times (p < 0.001), respectively. The gene discussed is IDO1; the disease is Stroke.