[Acute thrombocytopenia after obinutuzumab administration in a patient with relapsed follicular lymphoma]

A 64-year-old woman was admitted to our hospital because of relapsed follicular lymphoma. Obinutuzumab (OBZ) and bendamustine (GB) therapy was administered for her lymphoma, and thrombocytopenia requiring platelet transfusion was observed after the first course. Although the dose of bendamustine had been reduced, her thrombocytopenia was observed again after the second course. Complete remission of her lymphoma was achieved after 4 courses of GB therapy, and the patient was switched to OBZ maintenance therapy. Nevertheless, thrombocytopenia was observed again during the maintenance therapy with OBZ alone. Observing the platelet count that changed over time after OBZ administration in detail, the platelet count started to decrease 1 hour after the end of OBZ administration, decreased to half after 6 hours, reached the lowest value 4 days after administration, and gradually recovered from 10 days after administration. Although OBZ administration-associated thrombocytopenia is a relatively common complication, acute thrombocytopenia up to 24 hours after administration is rare. However, as in this case, thrombocytopenia may progress in an extremely short time after administration, and it is necessary for clinicians to pay attention to OBZ treatment.