Pulmonary veno-occlusive disease and/or pulmonary capillary hemangiomatosis (PVOD and/or PCH) constitutes a rare subgroup of pulmonary arterial hypertension (PAH; see this term) characterized by obliterative fibrosis of the small pulmonary veins and venules and/or capillary infiltration of the pulmonary interstitium leading to increased pulmonary vascular resistance and right ventricular dysfunction.