Background:Infliximab (IFX) is increasingly used in the management of severe, relapsing or refractory manifestations of Behçet Syndrome (BS). Emergence of de novo manifestations have been reported during IFX treatment, despite efficacy for the initial manifestation that required IFX use1.Objectives:We aimed to survey a sizeable cohort of BS patients treated with IFX for the development of de novo manifestations during treatment.Methods:A chart review was conducted to identify all BS patients who were given IFX in our Behçet Disease Research Center between 2004 and 2020. Demographic data, indications for IFX initiation, concomitant drugs, prior treatments, and outcomes were recorded. De novo manifestations were defined as new BS manifestations that had not occurred before IFX treatment.Results:A total of 252 patients used IFX with the main indications being uveitis in 122, vascular involvement in 82, parenchymal central nervous system involvement in 32, gastrointestinal involvement in 11, arthritis in 10, mucocutaneous involvement in 4, and secondary amyloidosis in 1. Of these patients, 17 (6%) had developed a total of 21 de-novo manifestations during a mean follow-up of 38.4 ± 92 (SD) months (Table 1). Vascular involvement was the main indication for IFX in the majority (n=12; 71%) of these 17 patients followed by eye involvement (n=3; 18%), central nervous system involvement (n=1), and joint involvement (n=1). Concomitant medications were prednisolone in 14 patients, azathioprine in 6 patients, mycophenolate mofetil, cyclosporine-A and methotrexate in 1 patient each. Thirteen patients (76%) were in remission for the main indication when de-novo manifestations emerged. In 10 patients IFX treatment was intensified either by increasing the dose to 10 mg/kg (2 patients) or by shortening the infusion intervals to 4 weeks (2 patients) along with the addition of corticosteroids or immunosuppressives. In the remaining 7 patients IFX was switched to another agent (cyclophosphamide in 5, adalimumab in 1 and anakinra in 1). At the time of this survey 8/17 patients were still on IFX for a mean follow-up of 32.5 ± 24.6 (SD) months, with concomitant low dose prednisolone in 5, azathioprine in 3 and mycophenolate mofetil in 3. In addition to the 7 patients who discontinued IFX at the time of de-novo manifestations, 2 more patients had discontinued IFX due to allergic reactions.Conclusion:De novo manifestations developed during IFX treatment in 6% of BS patients, despite efficacy for the initial manifestation. Appearance of de novo manifestations mostly in patients with vascular involvement is noteworthy. Intensification of IFX treatment was efficacious in managing de novo manifestations in more than half of these patients.References:[1]Hamuryudan V et al. Semin Arthritis Rheum. 2015;45(3):369-73.Table 1.Distribution of de novo manifestations that have emerged in 17 patientsDe-novo manifestations21Pulmonary artery aneurysm1Pulmonary artery thrombosis2Coronary artery involvement3Superficial thrombophlebitis5Arthritis5Erythema nodosum3Gastrointestinal involvement1Central nervous system involvement1Disclosure of Interests:None declared