Interferon beta-1a long-term therapy related to pulmonary arterial hypertension in multiple sclerosis patients.

We report two patients with relapsing remitting multiple sclerosis (RRMS) on interferon (IFN) beta-1a treatment for more than 7 years who developed pulmonary arterial hypertension (PAH). Patient 1 developed severe PAH requiring lung transplantation. Histology showed typical proliferative lesions including plexiform lesions consistent with PAH. Patient 2 ceased IFN beta-1a, and their symptoms stabilised. Both cases highlight IFN beta-1a treatment as a potential risk factor for PAH. PAH needs to be considered as a diagnosis in patients on long-term IFN beta-1a treatment who develop new-onset respiratory symptoms.