[Ferritin levels in adult Still's disease].

Adult-onset Still's disease (AOSD) is characterized by a spiking fever and diverse clinical findings; the diagnosis is often delayed for months or even years. The only positive laboratory finding is neutrophilic leukocytosis. Since 1987, the diagnostic importance of elevated serum ferritin levels has been discussed in numerous papers, but is not yet among the diagnostic criteria for AOSD. We describe a case in which the finding of extreme hyperferritinemia enabled prompt diagnosis and treatment.