A distinct form of PAH, pulmonary veno-occlusive disease (PVOD) or pulmonary capillary hemangiomatosis (PCH), was shown recently to be caused by homozygous mutations in eukaryotic translation initiation factor 2 alpha kinase 4 (EIF2AK4), a kinase in the integrated stress response (6, 8–10). This evidence concerns the gene EIF2AK4 and pulmonary venoocclusive disease.