Interstitial Pneumonitis Due to Janus Kinase Inhibitor Baricitinib in a Rheumatic Arthritis Patient

Abstract

A 68 years old rheumatoid arthritis patient received the janus kinase inhibitor baricitinib after a 2.5 years treatment with abatacept. Under abatacept she developed important cough, which was the reason to directly change to baricitinib. Within days cough was much aggravated and baricitinib treatment stopped after two weeks. The cough decreased, and six-week later baricitinib treatment was restarted. Within 14 days cough reappeared and novel exertional dyspnoea and hypoxaemia, aggravated with low exercise, and erythema at the face, neck, upper trunk, volar arms including wrists developed. Clinical findings, a novel restrictive lung function and gas diffusion impairment, and computer tomography were consistent with an acute pneumonitis due to baricitinib treatment. Baricitinib was stopped, and recovery was virtually complete within six weeks. We conclude that a very probable baricitinib pneumonitis occurred. To our knowledge, this is the first published case of this adverse effect in a rheumatoid arthritis patient.