| 1. PAH |
| 1.1. Idiopathic PAH |
| 1.2. Heritable PAH |
| 1.2.1. BMPR2 |
| 1.2.2. ALK1, ENG, SMAD9, CAV1, KCNK3 |
| 1.2.3. Unknown |
| 1.3. Drug and toxin induced |
| 1.4. Associated with: |
| 1.4.1. Connective tissue disease |
| 1.4.2. HIV infection |
| 1.4.3. Portal hypertension |
| 1.4.4. Congenital heart diseases |
| 1.4.5. Schistosomiasis |
| 1′ Pulmonary veno-occlusive disease and/or pulmonary capillary haemangiomatosis |
| 1″ Persistent PH of the newborn |
| 2. PH due to left heart disease |
| 2.1. Left ventricular systolic dysfunction |
| 2.2. Left ventricular diastolic dysfunction |
| 2.3. Valvular disease |
| 2.4 Congenital/acquired left heart inflow/outflow tract obstruction and congenital cardiomyopathies |
| 3. PH due to lung diseases and/or hypoxia |
| 3.1. COPD |
| 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 lung diseases |
| 4. CTEPH |
| 5. PH with unclear multifactorial mechanisms |
| 5.1. Haematological disorders: chronic haemolytic anaemia, myeloproliferative disorders, splenectomy |
| 5.2. Systemic disorders: sarcoidosis, pulmonary histiocytosis, lymphangioleiomyomatosis |
| 5.3. Metabolic disorders: glycogen storage disease, Gaucher disease, thyroid disorders |
| 5.4. Others: tumoural obstruction, fibrosing mediastinitis, chronic renal failure, segmental PH |
#: from the Fifth World Symposium on Pulmonary Hypertension (Nice, France, 2013). Reproduced from [7] with permission from the publisher.