- 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, or splenectomy), associated with significant venous or capillary involvement, pulmonary veno-occlusive disease, or pulmonary capillary hemangiomatosis.