EIF2AK4 and heritable pulmonary arterial hypertension: Mutations in the gene encoding bone morphogenetic protein receptor type II (<i>BMPR2</i>) have been associated with heritable pulmonary arterial hypertension (HPAH), whereas mutations in the gene encoding eukaryotic translation initiation factor 2 alpha kinase 4 (<i>EIF2AK4</i>) are associated with heritable pulmonary veno-occlusive disease/pulmonary capillary hemangiomatosis (HPVOD/PCH).