Ealed as a hard task. For this reason, the genotype-phenotype correlation has been performed grouping TAPI-2 biological activity mutations identified on the same gene, comparing the clinical and hemodynamic parameters with patients carrying only one pathogenic mutation and also with the group of patients without pathogenic mutations. The co-occurrence of several pathogenic mutations was more prevalent in women, which is in agreement with the higher prevalence of PAH in women10,11,38. However, Liu et al.43 postulated that the pathogenic mutations are more severe and prevalent in men for BMPR2 gene, suggesting hormonal implication. Our study did not corroborate such hypothesis, but it seems that the molecular basis of this disease could be more complex in women than men. The age of diagnosis was 11 years younger in patients with several mutations as previously described by Rodr uez-Viales et al.32 and Wang et al.33. These studies reported that patients carrying one or more pathogenic mutations exhibit an early age at diagnosis than patients without mutations. PVR were also significantly higher in patients with several mutations whereas the CI was lower. Furthermore, these patients had a worse response to treatment, compared with patients with a single or none mutation. This suggests that patients with several mutations need a more specifically treatment, in some cases directed to more than one cellular pathway. Accordingly, these patients seem to have a more severe illness and a worse prognosis. These results agree with those obtained by Rodr uez-Viales et al.32, who reported patients with several pathogenic mutations with a more severe phenotype. Also, in a previous study made by our group12, we pointed out that patients with several pathogenic mutations may show a greater predisposition to develop the disease. Three patients died after the follow-up period. They had an early age at diagnosis and were carriers of several pathogenic mutations. In addition, these patients did not respond to treatment, achieving a gradual increase of the characteristic phenotype of PAH leading to a premature death. These patients, as well as all cases with various pathogenic mutations, had a more severe phenotype and a higher functional class at diagnosis than patients without pathogenic mutations or with only a single one, but this small number does not allow us to perform statistical analysis. Our results are consistent with those obtained by other authors, but the small number of patients can be considered a limitation. However, the extensive genetic study and monitoring of our patients add extra values to our results. In summary, we report a series of IPAH and APAH patients with a high percentage of them carrying more than one pathogenic mutation in several genes. Moreover, BMPR2 was the more frequently affected gene, followed by ENG, ACVRL1 and KCNA5 genes. Some mutations had not been previously described. We cannot rule out that patients with a single pathogenic mutation have other mutations in genes not included in this study. There is no doubt that other genes could be involved in PAH and it will be important to understand their role in the development of the disease. Patients with several pathogenic mutations seem to show a more severe phenotype. We wonder whether these additional mutations act as a second event in the development of the disease, increasing the penetrance or simply modifying the phenotype of patients. Fifty-seven patients with CEP-37440 site idiopathic or associated PAH (g.Ealed as a hard task. For this reason, the genotype-phenotype correlation has been performed grouping mutations identified on the same gene, comparing the clinical and hemodynamic parameters with patients carrying only one pathogenic mutation and also with the group of patients without pathogenic mutations. The co-occurrence of several pathogenic mutations was more prevalent in women, which is in agreement with the higher prevalence of PAH in women10,11,38. However, Liu et al.43 postulated that the pathogenic mutations are more severe and prevalent in men for BMPR2 gene, suggesting hormonal implication. Our study did not corroborate such hypothesis, but it seems that the molecular basis of this disease could be more complex in women than men. The age of diagnosis was 11 years younger in patients with several mutations as previously described by Rodr uez-Viales et al.32 and Wang et al.33. These studies reported that patients carrying one or more pathogenic mutations exhibit an early age at diagnosis than patients without mutations. PVR were also significantly higher in patients with several mutations whereas the CI was lower. Furthermore, these patients had a worse response to treatment, compared with patients with a single or none mutation. This suggests that patients with several mutations need a more specifically treatment, in some cases directed to more than one cellular pathway. Accordingly, these patients seem to have a more severe illness and a worse prognosis. These results agree with those obtained by Rodr uez-Viales et al.32, who reported patients with several pathogenic mutations with a more severe phenotype. Also, in a previous study made by our group12, we pointed out that patients with several pathogenic mutations may show a greater predisposition to develop the disease. Three patients died after the follow-up period. They had an early age at diagnosis and were carriers of several pathogenic mutations. In addition, these patients did not respond to treatment, achieving a gradual increase of the characteristic phenotype of PAH leading to a premature death. These patients, as well as all cases with various pathogenic mutations, had a more severe phenotype and a higher functional class at diagnosis than patients without pathogenic mutations or with only a single one, but this small number does not allow us to perform statistical analysis. Our results are consistent with those obtained by other authors, but the small number of patients can be considered a limitation. However, the extensive genetic study and monitoring of our patients add extra values to our results. In summary, we report a series of IPAH and APAH patients with a high percentage of them carrying more than one pathogenic mutation in several genes. Moreover, BMPR2 was the more frequently affected gene, followed by ENG, ACVRL1 and KCNA5 genes. Some mutations had not been previously described. We cannot rule out that patients with a single pathogenic mutation have other mutations in genes not included in this study. There is no doubt that other genes could be involved in PAH and it will be important to understand their role in the development of the disease. Patients with several pathogenic mutations seem to show a more severe phenotype. We wonder whether these additional mutations act as a second event in the development of the disease, increasing the penetrance or simply modifying the phenotype of patients. Fifty-seven patients with idiopathic or associated PAH (g.
