Background:Giant cell arteritis (GCA) may affect the aorta and the large aortic branches and lead to dissections and aortic aneurysms. Tocilizumab (TCZ) treatment has the capacity to control aortic inflammation as has been demonstrated by CRP normalization and imaging data. However, limited data are available on the histopathological findings obtained from patients who underwent surgery because of aortic complications during TCZ treatment.Objectives:We report on 5 patients with aortitis who were treated with TCZ and developed aortic complications.Methods:We describe a retrospective case series of patients with GCA treated with TCZ, who presented in our clinic between 2011 and 2019. Three patients underwent surgery. Histopathologic examination was performed in specimen from all of them.Results:Five female patients were diagnosed with GCA (4/5) or Takaysu arteritis (1/5) involving the aorta, all them diagnosed by MR angiography and/or FDG PET CT scan. Three patients (one with aortic aneurysm, one with dissection) underwent surgery after having been treated with TCZ for seven weeks, nine months and four years, respectively. Imaging before surgery showed remission on MRI and/or PET-CT in all cases. At the time of surgery, all patients showed normalized CRP and ESR values. Histopathological evaluation of the aortic wall revealed infiltrates, consisting predominantly of CD3+CD4+ T cells. Enlargement of pre-existing aneuryms was observed in the other two patients 10 weeks and 4 months after discontinuation of TCZ, respectively. Both patients were not eligible for surgical intervention and died during follow-up.Conclusion:Our case series suggests that during treatment with TCZ, regular imaging is necessary in this patient population to detect development of structural changes such as aneurysms or dissections. Despite treatment, residual inflammation might persist which could contribute to eventual aortic complications.Disclosure of Interests:Andrea Rubbert-Roth Consultant of: Abbvie, BMS, Chugai, Pfizer, Roche, Janssen, Lilly, Sanofi, Amgen, Novartis, Peter Karl Bode: None declared, Thomas Langenegger: None declared, Claudia Pfofe: None declared, Thomas Neumann: None declared, Olaf Chan-Hi Kim: None declared, Johannes von Kempis Consultant of: Roche