Abstract: Objective To explore the risk and safety of tocilizumab (TCZ) induced hypofibrinogenemia in patients with rheumatic immune diseases. Methods The clinical data of hypofibrinogenemia caused by TCZ in the treatment of vasculitis in a child were retrospectively analyzed, and the relevant literature was reviewed. Results A 12 -year-old boy presented with a painful erythema-like rash on the limbs, accompanied by swelling and pain in the lower limbs and restricted mobility. The skin pathology showed vasculitis-like changes. The treatment effect of prednisone and cyclophosphamide in the child was not satisfactory. Hypofibrinogenemia occurred 2 weeks after the treatment with TCZ, and the level of fibrinogen increased 6 weeks after discontinuation of TCZ. There were minimal hemoptysis twice during the period. Foreign literature has reported that patients treated with TCZ have a higher risk of surgical bleeding. TCZ induced hypofibrinogenemia may be related to drug-induced cytokine imbalance and secondary coagulation factor ⅩⅢ deficiency. Conclusion TCZ treatment can cause hypofibrinogenemia and even secondary severe bleeding. The coagulation function should be monitored during the treatment process, especially the level of fibrinogen and the activity of coagulation factor ⅩⅢ.

Key words: vasculitis; tocilizumab; hypofibrinogenemia; coagulation factor ⅩⅢ; bleeding