Bimekizumab and progressive pulmonary fibrosis in severe psoriasis: a case report.

Psoriasis is a chronic immune-mediated inflammatory disease frequently associated with systemic comorbidities, including an increased prevalence of interstitial lung diseases (ILDs). Progressive fibrosing ILDs are characterized by declining respiratory function and high morbidity, and emerging evidence suggests that type-17 immune pathways may contribute to both psoriatic inflammation and pulmonary fibrosis. Bimekizumab, a monoclonal antibody selectively targeting IL-17A and IL-17F, has demonstrated high efficacy in psoriasis, although its potential impact on fibrotic lung disease remains unclear. We report the case of a 58-year-old man with severe plaque psoriasis and concomitant desquamative interstitial pneumonia (DIP) with features of progressive pulmonary fibrosis. The patient presented with severe restrictive lung disease, reduced diffusing capacity, and exertional desaturation requiring oxygen supplementation. Previous treatments included topical therapies, acitretin, and intermittent systemic corticosteroids, which contributed to worsening skin disease. Bimekizumab was initiated after appropriate screening, resulting in rapid and complete skin clearance by week 12, with no adverse events. Over a 14-month follow-up, a progressive improvement in respiratory function was observed, including increased spirometric parameters, improved diffusing capacity, and enhanced exercise tolerance, with resolution of exertional desaturation and discontinuation of oxygen support during mild activity. No other therapeutic changes were made during this period. Given the role of IL-17 cytokines in inflammation and fibrosis, this observation suggests a potential effect of IL-17A/F inhibition on fibrotic lung processes. This case highlights a possible dual benefit of bimekizumab in patients with psoriasis and concomitant ILD and supports further investigation into shared pathogenic pathways and targeted therapeutic strategies.