BMPR2 and pulmonary arterial hypertension: Heterozygous germline mutations in the bone morphogenetic protein type 2 receptor (BMPR2) have been identified as a gene underlying HPAH in approximately 10 to 40% of patients with apparently sporadic disease [1,3-6] and in 58% to 74% of patients with familial PAH [1,4,6,7].