Abstract
Systemic juvenile idiopathic arthritis (sJIA) is an autoinflammatory disease characterized by recurrent systemic inflammation, where the overproduction of cytokines, including interleukin (IL)-6 and -18. Tocilizumab (TCZ) is an effective IL-6 inhibitor for treating sJIA. Because TCZ masks signs of macrophage activating syndrome (MAS), such as fever and elevated serum ferritin levels, making MAS development less likely to be recognized, the timing of TCZ introduction requires careful consideration. We recently encountered two cases of sJIA where TCZ was introduced after achieving disease control through various treatments, including plasma exchange. In Case 1, a 5-year-old girl experienced persistent fever despite three courses of intravenous methylprednisolone pulse therapy (IVMP). We were concerned about MAS development due to decreasing platelet levels and a high IL-18 level of 92,200 pg/mL. TCZ was introduced after observing a decrease in IL-18 levels, following plasma exchange and administration of cyclosporin A (CyA). This approach resulted in success in controlling the disease. In Case 2, a 12-year-old girl exhibited thrombocytopenia during IVMP and was suspected to have MAS. TCZ was introduced after plasma exchange treatment, CyA, and dexamethasone palmitate. Following TCZ administration, this approach also resulted in success in controlling the disease. To avoid complications or exacerbations of MAS, it is essential to promptly evaluate platelet counts, IL-18, and ferritin levels, and initiating plasma exchange could be a treatment option.
