GWAS for platelet reactivity indicated a significant signal for CYP2C19*2 (P value = 1.67e33), and mutations in SCOS5P1, CDC42BPA, and CTRAC1 proved genome-wide significance in the CAD, percutaneous coronary intervention, and acute coronary syndrome subgroups (lowest P values: 1.07e-09, 4.53e-08, and 2.60e-10, respectively). The gene discussed is CYP2C19; the disease is acute coronary syndrome.