Obinutuzumab-induced Acute Thrombocytopenia Mimicking Immune Thrombocytopenia in a Patient with Follicular Lymphoma.

Obinutuzumab-induced acute thrombocytopenia is characterized by a rapid decrease in the platelet count after administration. The underlying mechanisms remain unclear. However, we present novel laboratory findings related to its pathophysiology. A 65-year-old woman with follicular lymphoma developed acute thrombocytopenia within 24 hours after obinutuzumab administration. Laboratory results showed features resembling acute immune thrombocytopenic purpura, including an elevated immature platelet fraction, mildly increased thrombopoietin levels, elevated platelet-associated immunoglobulin G, and refractory to platelet transfusion. Our case and her laboratory findings suggest that increased platelet consumption might be involved in the development of obinutuzumab-induced acute thrombocytopenia.