S1759 Rebound New Atopic Dermatitis in Patients With Inflammatory Bowel Disease Who Stop Janus Kinase Inhibitors

Introduction: Janus kinase inhibitors (JAKi) are a class of small molecule therapies used in several immune-mediated diseases, including inflammatory bowel disease (IBD) and atopic dermatitis (AD). Withdrawal of JAKi therapy in AD has been associated with disease relapse. However, the development of inflammatory skin lesions in patients with IBD who discontinue JAKi therapy has not previously been reported. We present a novel case series of 8 patients with IBD who developed de novo AD following the cessation of JAKi therapy. Methods: Between March 2023 to March 2025, we identified 8 patients with IBD who developed AD after withdrawal of JAKi therapy. Results: The mean age of the patients was 36.9 years (SD 9.2), with a median disease duration of 15 years (IQR 12-23). The median time from JAKi withdrawal to AD onset was 7 days (IQR 2-12). The rash was often described as pruritic and erythematous papules that were located on the face, anterior and posterior trunk, and upper extremities. Two patients underwent biopsies of their respective skin lesions that provided additional histopathological confirmation of AD. All patients were treated with either topical steroids or pimecrolimus and an oral antihistamine for newly diagnosed AD. Two patients experienced complete resolution of dermatologic lesions with topical prednisone and oral antihistamine therapy. The remaining 6 patients experienced complete resolution of their AD after eventual reinitiation of JAKi therapy for IBD management. Conclusion: We propose that a subset of patients with IBD may have latent susceptibility to AD, unmasked by therapy cessation and potentially triggered by an immune rebound phenomenon. The post-JAKi inflammation experienced by this patient population appears limited to the skin. It is notable that other types of rebound inflammation (e.g. arthritis) have not been reported. Given the increasing use of JAKi in IBD management, clinicians should be aware of this potential rebound phenomenon. Further research is needed to characterize its prevalence and pathogenesis and to develop strategies for prevention including identifying patients at risk and effective tapering strategies to mitigate symptoms.