IFNB1 and pulmonary arterial hypertension: Since 1993, there are reports of PAH associated with IFN-α injections.3 The first report of PAH following IFN-β treatment was in 2009;4 after that, other cases of patients with MS were detected who developed this serious condition after IFN-β treatment,3-7 but this side effect has been remained rare among IFN-β users.