Successful use of tocilizumab in a patient with rheumatoid arthritis following severe pancytopenia during etanercept therapy.

Severe cytopenia, including neutropenia and anemia, may occasionally occur during anti-tumor necrosis factor α (TNF-α) therapy. However, its mechanism is poorly understood, and little is known concerning the rationale of the choice of biologic therapy after a severe episode of cytopenia. The authors present the case of a 68-year-old rheumatoid arthritis patient in whom severe pancytopenia developed soon after the initiation of etanercept therapy. After resolution, the interleukin 6 receptor-blocking agent tocilizumab was introduced, which resulted in long-lasting complete remission of the rheumatoid arthritis without any adverse effects. The apoptosis-inducing effects of 3 TNF-α blockers and tocilizumab on peripheral blood mononuclear cells of the patient were compared by means of annexin V and propidium iodide labeling and flow cytometry. In concert with the clinical events, the anti-TNF-α agents demonstrated significantly higher apoptotic activities than that of tocilizumab. Tocilizumab appeared safe after anti-TNF-α-induced cytopenia possibly caused by apoptosis induction.