| 1. Pulmonary arterial hypertension |
| 1.1 Idiopathic pulmonary arterial hypertension |
| 1.2 Heritable |
| 1.2.1. BMPR2 |
| 1.2.2. ALK1, endoglin (with or without hereditary haemorrhagic telangiectasia) |
| 1.2.3 Unknown |
| 1.3 Drug- and toxin-induced |
| 1.4 Associated with: |
| 1.4.1 Connective tissue diseases |
| 1.4.2 HIV infection |
| 1.4.3 Portal hypertension |
| 1.4.4 Congenital heart diseases |
| 1.4.5 Schistosomiasis |
| 1.4.6 Chronic haemolytic anaemia |
| 1.5 Persistent pulmonary hypertension of the newborn |
| 1'. Pulmonary veno-occlusive disease and/or pulmonary capillary haemangiomatosis |
| 2. Pulmonary hypertension due to left heart disease |
| 2.1 Systolic dysfunction |
| 2.2 Diastolic dysfunction |
| 2.3 Valvular disease |
| 3. Pulmonary hypertension 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. Chronic thromboembolic pulmonary hypertension |
| 5. Pulmonary hypertension with unclear and/or multifactorial mechanisms |
| 5.1 Haematological disorders: myeloproliferative disorders splenectomy |
| 5.2 Systemic disorders, sarcoidosis, pulmonary Langerhans cell histiocytosis, lymphangioleiomyomatosis, neurofibromatosis, vasculitis |
| 5.3 Metabolic disorders: glycogen storage disease, Gaucher disease, thyroid disorders |
| 5.4 Others: tumoural obstruction, fibrosing mediastinitis, chronic renal failure on dialysis |
BMPR2: bone morphogenetic protein receptor, type II; ALK1: activin receptor-like kinase 1 gene. Reproduced from [2] with permission from the publisher.