Table 2.

World Health Organization's classification of pulmonary hypertension^[10]

Group I - Pulmonary Arterial hypertension (PAH)

Idiopathic PAH

Heritable PAH (BMPR2, ALK1, ENG, SMAD9, CAV1, KCNK3, Unknown)

Drug and toxin induced

Associated with (1) Connective tissue disease; (2) HIV infection; (3) Portal hypertension; (4) Congenital heart disease; and (5) Schistosomiasis

Pulmonary veno-occlusive disease and/or pulmonary capillary hemangiomatosis

Persistent pulmonary hypertension of the newborn

Group II - Pulmonary hypertension due to left heart disease

Left ventricular systolic dysfunction

Left ventricular diastolic dysfunction

Valvular disease

Congenital/acquired left heart inflow/outflow tract obstruction and congenital cardiomyopathies

Group III - Pulmonary hypertension due to lung diseases and/or hypoxia

Chronic obstructive pulmonary disease

Interstitial lung disease

Other pulmonary diseases with mixed restrictive and obstructive pattern

Sleep-disordered breathing

Alveolar hypoventilation disorders

Chronic exposure to high altitudes

Developmental lung disease

Group IV - Chronic thromboembolic pulmonary hypertension

Group V - Pulmonary hypertension with unclear multifactorial mechanisms

Hematologic disorders: chronic hemolytic anemia, myeloproliferative disorders, splenectomy

Systemic disorders: sarcoidosis, pulmonary histiocytosis, lymphangioleimyomatosis

Metabolic disorders: glycogen storage disease, Gaucher’s disease, hypothyroidism

Others: tumoral obstruction, fibrosing mediastinitis, chronic renal failure, segmental pulmonary hypertension

Adapted from Galiè et al^[62]. BMPR: Bone morphogenic protein receptor type II; CAV1: Caveolin-1; ENG: Endoglin; HIV: Human immunodeficiency virus.