[A case of severe systemic juvenile idiopathic arthritis introduced tocilizumab in early phase of the disease].

A 14-year-old boy was admitted in the former hospital with remittent fever, erythematous rash, joint pain, and muscle pain. Antibiotics were ineffectively administered and then, methylprednisolone (mPSL) pulse therapy with methotrexate was introduced under the diagnosis of suspected systemic juvenile idiopathic arthritis (JIA). However, he still had clinical symptoms and signs, and was transferred to our hospital. Re-examination revealed no malignancies including acute leukemia by bone marrow aspiration, no infectious agents by septic work, and no significant increases of antibodies against several viruses including CMV, EBV, HSV, Parvovirus B19, adenovirus, and so forth. FDG-PET demonstrated the accumulation of (18)F-FDG in bone marrows suggesting systemic JIA. Laboratory findings were leukocytosis and granulocytosis, elevated levels of C-reactive protein, D-dimer, ferritin, and interleukin-6. He was finally diagnosed as having severe systemic JIA. Thus, soon after the additional mPSL pulse therapy, tocilizumab (TCZ) was successfully introduced. In conclusion, for systemic JIA patients with severe systemic inflammation, it will be reasonable to introduce tocilizumab earlier than the guideline suggested to reduce side effects of long-term and large amounts of steroids and to protect the transition to macrophage activation syndrome. Further studies will be needed to recommend appropriate timing of tocilizumab introduction.