this is the case of man aged 51 admitted due to odynophagia, high fever, polyarthritis, as well as leukocytes with neutrophilia and accelerated erythrosedimentation. during admission it was noted polyserositis, pneumonitis and myocarditis with left cardiac insufficiency, hyper-transaminasemia, hyper-ferritinemia and rheumatoid factor with anti-and of negative double-chain. treatment was started with corticosteroids and immunosuppressive agents (azathioprine). response was not the expected one and it was necessary to change the immunosuppressive agent by methotrexate. febrile polyarthritis of polycyclic evolution is the more frequent presentation of the still's disease in adult. hyper-ferritinemia over 1 000 ng/ml is an useful tool for diagnosis and its normalization is an indicator of therapeutical success. there were neither clinical manifestations nor pathognomonic laboratory tests thus, diagnosis remains by exclusion.