AB0217 ARE WE MISSING HYPOFIBRINOGENEMIA FOLLOWING TOCILIZUMAB TREATMENT? A SINGLE CENTRE RETROSPECTIVE RESULTS
Authors: R. Yildirim, D. Üsküdar Cansu, M. Dinler, C. Korkmaz
Journal: Annals of the Rheumatic Diseases (2024)

<h3>Background:</h3> Tocilizumab (TCZ), monoclonal antibody against IL-6, is an effective treatment option in rheumatoid arthritis and giant cell arteritis. <h3>Objectives:</h3> Common adverse reactions including elevated liver enzymes, neutropenia and lipid abnormalities are well described in patients on TCZ. However, decline in fibrinogen level is an atypical finding that has been increasingly reported in case series. In this study, we aimed to investigate hypofibrinogenemia in patients receiving TCZ in our cohort. <h3>Methods:</h3> We retrospectively screened our biologic data to extract those whom were given TCZ between 2015 and 2023 in the department of rheumatology in Eskişehir Osmangazi University. After that patients whose fibrinogen levels were studied after TCZ at least once were recruited and demographic features (age, gender), clinical and laboratory findings (erythrocyte sedimentation rate (ESH), C-reactive protein (CRP), fibrinogen) before and after TCZ, and management were recorded. <h3>Results:</h3> Characteristics of 30 patients were summarized in Table 1. In total, hypofibrinogenemia was found in 13 (43.3%) of whom 7 were known to have normal fibrinogen before TCZ. Symptoms including petechiae and ecchymoses were detected in 4, with no bleeding being reported. Mean fibrinogen level after TCZ was found to be 208.40 ± 88.69 mg/dl (min 92 max 468) and 144,54 ± 20,39 (min 92 max 171) in entire and hypofibrinogenemic groups, respectively. TCZ was switched to another medication in 6. Among hypofibrinogenemic patients, all showed elevation following TCZ cessation. No information regarding fibrinogen was available in 7 during follow-up. Gender (p=0.698), platelets (p=0.513), ESH (p=0.515) and CRP (p=0.615) at the time of TCZ initiation were not found to be associated with hypofibrinogenemia development. <h3>Conclusion:</h3> Our cohort showed that hypofibrinogenemia might develop after TCZ treatment in nearly half of patients, which is relatively novel for routine clinical practice. More than half of them were asymptomatic and all were reversible. The major limitation of our study is the retrospective design, therefore prospective large cohort studies are needed to enlighten the nature of low fibrinogen in TCZ given population. <h3>REFERENCES:</h3> [1] He T, Ling J, Yang J. Tocilizumab-induced hypofibrinogenemia in patients with systemic-onset juvenile idiopathic arthritis. Sci Rep. 2023;13(1):9050. Published 2023 Jun 3. doi:10.1038/s41598-023-36246-6. [2] Üsküdar Cansu D, Demirtaş E, Andiç N, Üsküdar Teke H, Korkmaz C. Is it required to routinely check fibrinogen level in patients with rheumatic diseases on tocilizumab? Case-based review. Rheumatol Int. 2019;39(4):743-750. doi:10.1007/s00296-019-04268-x. <b>Table 1.</b> Characteristics of 30 patients on tocilizumab in our study <i>RA: rheumatoid arthritis, GCA: giant cell arteritis, JIA: juvenile idiopathic arthritis, TCZ: tocilizumab, sc: subcutaneous, iv: intravenous, N: number, ESH: erythrocyte sedimentation rate, CRP: C-reactive protein</i> <h3>Acknowledgements:</h3> <b>NIL.</b> <h3>Disclosure of Interests:</h3> <b>None declared.</b>