Pulmonary hypertension: how to differentiate rare from frequent etiologies?

Pulmonary hypertension (PH) is a frequent finding. PH secondary to left heart diseases is the most prevalent form of PH. PH caused by lung diseases and/or hypoxia is the second most frequent cause. The patient should be addressed to an expert center if the PH does not seem to be secondary to a left heart disease or a lung disease, if the PH seems too severe for the underlying cardiac or pulmonary diseases or in the presence of risk factors for PH caused by rare etiologies (group 1, 4 and 5).