PDGFD is a newly identified risk gene in PAH [14]; this analysis offers the first independent validation of its causal association with PAH, as well as confirming a specific role in the development of paediatric disease through the identification of a rare missense variant (c.550G>A, p.Glu184Lys) in a female cPAH patient (Figure 1C). This evidence concerns the gene CPA6 and pulmonary arterial hypertension.