Extremely high serum ferritin levels as a main diagnostic tool of adult-onset Still's disease.

Adult-onset Still's disease is a rare systemic inflammatory disease of unknown aetiology characterised by typical symptoms including daily high spiking fever, evanescent salmon-pink rash, sore throat, arthritis/arthralgias and polyserositis. The laboratory findings usually show neutrophilic leucocytosis, seronegativity and raised serum transaminases. We describe six typical cases. All of them had serum ferritin above 5,000 µg/L. Although there are few theories about the origin of the high ferritin level, an extremely high serum ferritin above 5,000 µg/L should be the main diagnostic tool of adult-onset Still's disease.