| 1. PAH |
| 1.1. Idiopathic PAH |
| 1.2.Heritable |
| 1.2.1 BMPR2 gene mutation |
| 1.2.2 ALK1, endoglin (with or without hereditary haemorrhagic telangiectasia) gene mutation |
| 1.2.3 Unknown |
| 1.3. Drug- and toxin-induced |
| 1.4. APAH |
| 1.4.1. Connective tissue diseases |
| 1.4.2. HIV infection |
| 1.4.3. Portal hypertension |
| 1.4.4. Congenital heart disease |
| 1.4.5. Schistosomiasis |
| 1.4.6. Chronic haemolytic anaemia |
| 1.5. Persistent PH of the newborn |
| 1′. Pulmonary veno-occlusive disease and/or pulmonary capillary haemangiomatosis |
| 2. PH due to left heart disease |
| 2.1. Systolic dysfunction |
| 2.2. Diastolic dysfunction |
| 2.3. Valvular disease |
| 3. PH due to lung diseases and/or hypoxia |
| 3.1. Chronic obstructive pulmonary disease |
| 3.2. Interstitial lung disease |
| 3.3. Other pulmonary diseases with mixed restrictive and obstructive pattern |
| 3.4. Sleep-disordered breathing |
| 3.5. Alveolar hypoventilation disorders |
| 3.6. Chronic exposure to high altitude |
| 3.7. Developmental abnormalities |
| 4. CTEPH |
| 5. PH with unclear and/or multifactorial mechanisms |
| 5.1. Haematological disorders: myeloproliferative disorders and splenectomy |
| 5.2. Systemic disorders, sarcoidosis, pulmonary Langerhans cell histiocytosis, lymphangioleiomyomatosis, neurofibromatosis and vasculitis |
| 5.3. Metabolic disorders: glycogen storage disease, Gaucher disease and thyroid disorders |
| 5.4. Others: tumoural obstruction, fibrosing mediastinitis and chronic renal failure on dialysis |
PAH: pulmonary arterial hypertension; BMPR2: bone morphogenetic protein receptor, type 2; ALK1: activin receptor-like kinase 1; APAH: associated PAH; CTEPH: chronic thromboembolic PH.