LAUSR

OBJECTIVES Vedolizumab (VDZ) blocks α4β7 integrin and is licenced for the treatment of IBD. It has been associated with mild SpA-related features, including sacroiliitis and synovitis. Herein we report a series of cases demonstrating the emergence of severe SpA-associated enthesitis/osteitis following successful IBD therapy with VDZ. METHODS We evaluated 11 VDZ-treated patients with IBD across seven centres who developed severe active SpA and/or enthesopathy, with the aim of characterizing the VDZ-associated SpA or entheseal flares. Imaging features demonstrating particularly severe disease were recorded. RESULTS De novo SpA developed in 9 of 11 patients and flare of known SpA in 2 patients, with 4 patients requiring hospitalization due to disease severity. Available data showed that one of seven cases were HLA-B27 positive. The median time from VDZ initiation to flare was 12 weeks, with IBD well controlled in 7 of 10 patients (no data for 1 patient) at flare. Severe SpA enthesitis/osteitis was evident on MRI or US, including acute sacroiliitis (n = 5), extensive vertebral osteitis (n = 1), peri-facetal oedema (n = 1) and isolated peripheral enthesitis (n = 3). Due to arthritis severity, VDZ was discontinued in 9 of 11 patients and a change in therapy, including alternative anti-TNF, was initiated. CONCLUSION Severe SpA, predominantly HLA-B27 negative, with osteitis/enthesitis may occur under successful VDZ treatment for IBD, including in subjects with prior anti-TNF therapy for intestinal disease.