Table 1.

Clinical classification of PH

Group 1: PAH

1.1 Idiopathic PAH

1.2 Heritable PAH (BMPR2, ALK1, endoglin, SMAD9, CAV1, KCNK3, unknown)

1.3 Drug- and toxin-induced

1.4 Associated with: connective tissue diseases; HIV infection; portal hypertension; congenital heart disease; schistosomiasis

Group 1’: Pulmonary veno-occlusive disease and/or pulmonary capillary hemangiomatosis

Group 1”: Persistent PH of the newborn

Group 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

Group 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 lung diseases

Group 4: Chronic thromboembolic PH

Group 5: PH with unclear multifactorial mechanisms

5.1 Hematologic disorders: chronic hemolytic anemia; 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: tumoral obstruction; fibrosing mediastinitis; chronic renal failure; segmental PH

Abbreviations: PAH, pulmonary arterial hypertension; PH, pulmonary hypertension; ALK-1, activin receptor-like kinase 1 gene; BMPR2, bone morphogenetic protein receptor, type 2; CAV1, caveolin-1; KCNK3, gene encoding potassium channel super family K member-3; SMAD9, mothers against decapentaplegic 9.