Group 1: Pulmonary arterial hypertension Idiopathic Heritable: associated with specific gene mutations like BMPR2, ALK1, endoglin, etc Drug- & toxin-induced Associated with: connective tissue diseases, HIV infection, portal hypertension, congenital heart diseases, schistosomiasis & chronic hemolytic anemia Persistent pulmonary hypertension of the newborn Group 1': Pulmonary veno-occlusive disease and/or pulmonary capillary hemangiomatosis Group 2: PH secondary to left heart disease Systolic dysfunction Diastolic dysfunction Valvular disease Group 3: PH secondary to lung diseases and/or hypoxia Chronic obstructive pulmonary disease Interstitial lung disease Other diseases with a mixed restrictive & obstructive pattern Sleep disordered breathing Alveolar hypoventilation disorders Chronic exposure to high altitude Developmental abnormalities Group 4: Chronic thromboembolic pulmonary hypertension Group 5: PH due to multi-factorial/unclear mechanisms. Hematologic: myeloproliferative disorders, splenectomy Systemic: sarcoidosis, pulmonary Langerhans cell histiocytosis Metabolic disorders: glycogen storage disorders, Gaucher disease, thyroid disorders Others: tumoral obstruction, fibrosing mediastinitis, chronic renal failure on dialysis

Table 1: Updated clinical classification of pulmonary hypertension [4] (Dana Point, 2008).