Risk-related haplotypes (MCP-H2 in 11 patients, CFH-H3 in 3 patients, and CFHR1∗B in 2 patients; Supplementary Table S1) were identified alone or together with other haplotypes in a total of 15 of 37 (40.5%) patients (36.0% of PPH vs. 50.0% no PPH, P = 1.0 for difference between groups). This evidence concerns the gene CFH and pulmonary arterial hypertension.