Behçet's disease occurred after brodalumab initiation in a patient with chronic non-bacterial osteitis: a case-based literature review.

Interleukin-17 (IL-17) inhibitors are established therapies for various immune-mediated diseases, while paradoxical reactions may occur following their initiation. Although a few cases of Behçet’s disease have been reported following IL-17A inhibition, its occurrence during treatment with IL-17 receptor inhibitor has not been reported. Herein, we report the first case of Behçet’s disease that developed as a paradoxical reaction to brodalumab, an IL-17 receptor inhibitor, in a patient being treated for chronic non-bacterial osteitis with palmoplantar pustulosis. Despite initial improvement of the underlying condition, the patient developed characteristic Behçet’s disease manifestations, including oral and genital ulcers, and cutaneous symptoms shortly after initiating brodalumab. Symptoms resolved following drug discontinuation and treatment with colchicine and apremilast. Our literature review identified 12 previous cases of Behçet’s disease which developed after IL-17 inhibitor initiation. All cases stopped IL-17 inhibitors after the onset of Behçet’s disease, and nine cases were treated with systemic glucocorticoids. This case-based review suggests that broad inhibition of the IL-17 pathway may disrupt cytokine balance or mucosal homeostasis, potentially contributing to the development of Behçet’s disease. Clinicians should be aware of this rare complication, as early recognition and prompt cessation of the causative IL-17 inhibitor are essential for effective clinical management of this paradoxical reaction.