NOS3 and chronic thromboembolic pulmonary hypertension: Similar to the results from the study by Suntharalingam et al [21], a study by Ulrich and colleagues [28], which looked into polymorphisms other than those in fibrinogen, namely in bone morphogenetic protein receptor 2 (BMPR2), serotonin transporter (5-HTT) or receptor (5-HTR-2A), and the endothelial nitric oxide synthase (eNOS) genes, did not identify any significant association between the presence of a polymorphism and the presence of CTEPH or the clinical presentation of the patients.