RESUMO
Renal cell carcinoma (RCC) accounts for majority of malignancies arising out of the kidney. Paraneoplastic rheumatologic manifestations; myositis, vasculitis, and arthritis have been described in a few cases with RCC. Systemic onset juvenile idiopathic arthritis (JIA) is characterized by intermittent fever, arthritis, reticulo-endothelial cell hyperplasia and absence of rheumatoid factor and antinuclear antibodies. Herein, we report a 16-year-old boy with systemic onset JIA for 5 years who developed RCC and his systemic and articular symptoms paralleled the course of RCC. The common pathophysiologic influence of the cytokine Interleukin-6 possibly played a role in the exacerbation of symptoms of systemic onset JIA during the relapse of the RCC. The case is presented to highlight the rare co-occurrence of these two diseases and their influence on each other.