Table 1. Updated clinical classification of pulmonary hypertension
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.