CYP2C9*3 is associated with PHT-induced rash (OR: 7.05; 95% CI: 2.44–20.4; p = 0.0022).HLA-B*51:01 also showed association (OR: 3.19; 95% CI: 1.37–7.48; p = 0.010). This evidence concerns the gene HLA-B and pulmonary hypertension, primary, 1.