Rapid tumor lysis in a patient with B-cell chronic lymphocytic leukemia and lymphocytosis treated with an anti-CD20 monoclonal antibody (IDEC-C2B8, rituximab).

In this report we present a patient with B-cell chronic lymphocytic leukemia who developed an acute tumor lysis syndrome after administration of the human anti-CD20 antibody IDEC-C2B8 (RITUXIMAB) in standard dose of 375 mg/m2. IDEC-C2B8 has been demonstrated to have only mild and tolerable side effects in patients with follicular lymphoma. In these trials patients with lymphocytosis >5000/microl were excluded. Physicians must be aware of this hitherto unreported phenomenon in patients with high CD20-positive blood counts.