Abstract

Tocilizumab is a monoclonal antibody directed against the interleukin-6 receptor and used for the treatment of rheumatoid arthritis (RA). However, patients treated with tocilizumab have risk of infection, such as necrotizing fasciitis (NF). We report two cases of NF involving patients who had been treated with tocilizumab, and highlight the risk of serious soft tissue infection. Case 1:A 79-year-old woman, who had been treated with tocilizumab for RA, developed NF in her left leg. However, both the white blood cell (WBC) count and C-reactive protein (CRP) were within their normal ranges. Debridement of infectious soft tissue was performed immediately, and the wound was resurfaced with a free skin graft 3 weeks after the primary surgery. Case 2:A 63-year-old woman who had been treated with tocilizumab for RA developed NF in her right thigh. She showed a normal WBC count and CRP level at the first examination. Debridement was performed immediately, and the wound was resurfaced with a free skin graft 4 weeks later. It was difficult to make an initial diagnosis of NF, because inflammatory signs, such as WBC and CRP elevation, were absent. This paradoxical phenomenon is explained by the influence of IL-6 blocking therapy. Appropriate diagnostic methods, including computed tomography imaging and exploratory incision, should be performed for an early diagnosis, which can improve the prognosis of patients with NF following tocilizumab treatment.

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