Tocilizumab may not be a good option for vascular involvement due to Behçet's syndrome.

Objectives: Tocilizumab has been increasingly reported as an alternative therapeutic agent in the management of Behçet's syndrome (BS) and it has been mostly tried in BS patients with neurological and eye involvement. As therapeutic responses to each drug may vary across different types of BS involvement, we aimed to report seven patients with large vessel involvement treated with tocilizumab.

Methods: We enrolled seven BS patients with vascular involvement who were given tocilizumab at the Behçet's Disease Research Centre in Istanbul University-Cerrahpaşa between 2000 and 2022. Demographic information, BS features, types of vascular involvement, previous and concomitant medications, C-reactive protein (CRP) levels, imaging modality results, and outcomes were documented from the patients' medical records.

Results: Within a median of 6 months after the initiation of tocilizumab, 5 patients experienced vascular relapses. These relapses included the emergence of new bilateral pulmonary artery aneurysms, a new pulmonary artery thrombus, parenchymal lung involvement, deep vein thrombosis in the lower extremity, and pseudotumor cerebri in one patient each. CRP levels were normal in 4 of the 5 patients at the time of vascular relapse. One of these 5 patients and another patient with aortitis had an exacerbation of mucocutaneous symptoms. In the last patient, venous ulcers did not respond to tocilizumab and were complicated with infection.

Conclusions: Tocilizumab could potentially exacerbate vascular manifestations, similar to what is observed with mucocutaneous lesions in BS patients. Furthermore, CRP levels appear to be ineffective in monitoring these patients.