Abstract: Objective To analyze the clinical characteristics and pathogenesis of obinutuzumab injection induced acute severe thrombocytopenia based on real cases in order to improve clinical vigilance on a rare adverse reaction induced by obinutuzumab. Methods The clinical medication for and changes in blood platelets count of a 61-year-old male patient with follicular lymphoma who suffered from acute severe thrombocytopenia caused by the combination of obinutuzumab and chemotherapy were analyzed, and related literature was consulted. Results Acute severe thrombocytopenia occurred following chemotherapy with the G-CHOP regimen (obinutuzumab, cyclophosphamide, pirarubicin, vindesine and prednisone). After causality assessment, obinutuzumab was discontinued. The patient immediately received combined treatment with intravenous immunoglobulins, thrombopoietin, and romiplostim. Subsequently, the platelets count returned to normal. The above adverse reactions did not occur when rituximab replaced obinutuzumab. Conclusion When a patient uses obinutuzumab for the first time, clinicians should care about platelets count and watch for bleeding symptoms. Before bone marrow suppression and in its absence, obinutuzumab-induced acute thrombocytopenia should be taken into consideration in case of acute thrombocytopenia. Pharmacovigilance and risk management are required.

Key words: Obinutuzumab, Rituximab, Injection, Acute Thrombocytopenia, Follicular Lymphoma, Adverse Drug Reaction