S4927 Ustekinumab Associated Vision Loss and Orbital Myositis in a Patient With Crohn’s Disease: A Rare Adverse Effect

Introduction: Ustekinumab (UST) is a monoclonal antibody that blocks the IL12 and IL23 inflammatory cytokines, used in many autoimmune conditions including Inflammatory Bowel Disease. Orbital myositis (OM) related to UST use is a novel adverse effect, with only few cases described in literature. OM may also present as a rare extra-intestinal manifestation in IBD making causality difficult to establish. We present the case of a young man with Crohn’s Disease who developed OM shortly after initiating UST therapy. Case Description/Methods: A 27-year-old White man with a history of Ileo-colonic Crohn’s disease diagnosed at age 14, status post ileocolectomy, had been maintained on infliximab therapy for the past 12 years. Surveillance colonoscopy revealed a non-traversable ileocolonic anastomotic stricture with minimal colitis. Due to concurrent abdominal pain, his treatment was transitioned to UST. Within 3 weeks of initiating UST, he developed severe headaches, bilateral upper eyelid swelling, proptosis, chemosis, ophthalmoplegia, and rapid vision loss in the left eye. Radiologic imaging demonstrated bilateral diffuse thickening of the extraocular muscles and periorbital edema. Thyroid eye disease was excluded. A left orbital and optic nerve decompression was performed but yielded limited improvement due to extensive fibrosis of the orbital muscles. Histopathological analysis of the orbital tissue revealed benign fibroconnective tissue with chronic inflammatory infiltrates. After receiving 2 doses of UST, the patient was switched back to infliximab and started on a prednisone taper. This resulted in improvement of the ophthalmoplegia and proptosis; however, the left-sided vision loss persisted a year later. Discussion: Our report describes the third documented case of UST associated OM in a patient with CD, and the only reported case resulting in persistent vision loss despite corticosteroid therapy and discontinuation of UST. Establishing a definitive causal relationship remains challenging, as both CD and UST treatment may contribute to this complication. It is also essential to rule out thyroid ophthalmopathy as a differential. In this case, the acute onset of symptoms shortly after initiating UST suggests a strong temporal association. This case highlights the need for careful consideration when switching advanced therapies and emphasizing the importance of close monitoring during and after treatment initiation including ophthalmology visit prior to and after initiation of UST therapy.