Group 1 pulmonary arterial hypertension (PAH) that occurs without a known cause often is called primary PAH or idiopathic (id-ee-o-PATH-ick) PAH.
Group 1 PAH that occurs with a known cause often is called associated PAH. For example, PAH that occurs in a person who has scleroderma might be called "PAH occurring in association with scleroderma," or simply "scleroderma-associated PAH."
Groups 2–5 pulmonary hypertension (PH) sometimes are called secondary PH.
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