Processes suggested to date include granulomatous involvement of pulmonary veins manifesting clinically as pulmonary veno-occlusive disease, extrinsic compression by mediastinal or hilar adenopathy, cardiac involvement including systolic or diastolic dysfunction, increased production of vasoactive endothelin-1 and downstream effects of hypoxemia.[20, 25, 29–31] Because of the plethora of possible mechanisms and a lack of understanding of the precise pathogenesis, PH related to sarcoidosis falls into group 5 (the ‘miscellaneous’ category) in the recent clinical classification of PH.[32]. The gene discussed is EDN1; the disease is sarcoidosis.