Objective Various antiviral therapies, including interferon therapy, are being conducted to treat chronic hepa-

Adult patients with ANCA-associated vasculitis (AAV) could be often complicated by other rheumatic diseases such as rheumatoid arthritis and systemic lupus erythematosus but which is rare in children. We report two children with microscopic polyangiitis (MPA) complicated by Polyarticular RF-positive juvenile idiopathic arthritis. Case 1 was a 23year-old female. She developed MPA at the age of 10. She had achieved remission by methylprednisolone pulse therapy (MPT) and intravenous cyclophosphamide. However, arthritis occurred 16 months later and she was diagnosed with pJIA. Methotrexate (MTX) was added and arthritis was resolved. Case 2 was a 14-year-old female. She developed arthritis at the age of 11. She was diagnosed as having pJIA two years later. She was initially treated with prednisolone, MTX and etanercept. However, she presented hematuria and proteinuria at the age of 14 and was diagnosed with MPA. MPT combined with rituximab significantly ameliorated her symptom. Although concomitance of pJIA and AAV is quite rare, considering its possibility is important when patients developed unexpected clinical symptoms. Furthermore, it is important to choose of therapy which can simultaneously cover bothdiseases, especially therapy for MPA is associate with the prognosis.