DDAH1 and pulmonary hypertension: We found four genes to be significantly associated with high-altitude pulmonary hypertension (i.e., estimated mPAP ≥ 30 mm Hg) after adjustment for multiple testing (Figure 3): NOS3 rs2070744 (p = 0.003), ARG2 rs3742879 (p = 0.003), DDAH1 rs233122 (p = 0.004), and AGXT2 rs37369 (p = 0.003).