- WHO Group 1 Pulmonary Arterial Hypertension: Idiopathic, Familial, Associated with (APAH) Collagen vascular disease, congenital systemic-to-pulmonary shunts, portal hypertension, Drugs and toxins (e.g., anorexigens, rapeseed oil, L-tryptophan, methamphetamine, and cocaine), other (thyroid disorders, glycogen storage disease, Gaucher disease, hereditary hemorrhagic telangiectasia, hemoglobinopathies, myeloproliferative disorders, splenectomy) Associated with significant venous or capillary involvement, Pulmonary veno-occlusive disease, Pulmonary-capillary hemangiomatosis.