The identification of heterozygous germline mutations in the bone morphogenetic protein Type II receptor (BMPR2) gene3,4 and the more recent identification of loss-of-function mutations in other BMP pathway components5 have underpinned potential PAH therapies to enhance BMP signalling.6 However, some rare PAH-related genes appear distinct from the BMP pathway,5,7 suggesting additional mechanisms underlying the pathobiology of PAH that may be informative for alternative therapies. The gene discussed is BMPR2; the disease is pulmonary arterial hypertension.