Presentation and diagnosis of adult-onset Still's disease: the implications of current and emerging markers in overcoming the diagnostic challenge.

Adult-onset Still's disease (AOSD) is a known cause of fever of unknown origin. It is characterized by a triad of symptoms: spiking fever (>39°C), salmon-colored rash and arthritis/arthralgia. On a predisposing genetic background, several conditions may act as trigger for disease and among these, infectious agents are the most important. Nowadays, a dichotomous view of AOSD has been introduced which distinguishes this entity in two subsets according to the clinical features and laboratory aspects: systemic or articular. As AOSD is a diagnosis of exclusion, specific biomarkers able to facilitate differential diagnosis are needed. A number of possible biomarkers have been proposed that will be discussed in detail in this review: ferritin, IL-18, procalcitonin, s100 proteins and sCD163.