The World Health Organization (WHO) has grouped Pulmonary Hypertension into five categories
WHO Group 1 is Pulmonary Arterial Hypertension (PAH). This includes
- PAH that has no known cause (Idiopathic)
- PAH that is familial or genetically inherited (hereditary)
- PAH associated with connective tissue disease, congenital heart disease, severe liver disease, HIV infection, or the use of certain diet medications
WHO Groups 2 to 5 PH are linked to other conditions or diseases.
WHO Group 2 is PH due to left-sided heart disease, such as heart failure or high blood pressure.
WHO Group 3 is PH due to lung conditions such as COPD (chronic obstructive pulmonary disease), interstitial lung disease, and sleep apnea. WHO Group 4 is PH related to multiple or recurrent blood clots (pulmonary embolism) in the lungs.
WHO Group 5 is PH related to other diseases or conditions. Examples include diseases such as sarcoidosis, rare diseases such as lymphangioleiomyomatosis (LAM) and mediastinal fibrosis. This type can also be due to tumours putting pressure on the pulmonary arteries.