ReviewSystemic juvenile idiopathic arthritis
Highlights
► sJIA is sets well apart from all the other forms of JIA. ► Autoinflammatory mechanisms seem to play a major role in the pathogenesis. ► IL-1 and IL-6 blockers are effective and will change the long term prognosis of JIA.
Introduction
Juvenile idiopathic arthritis (JIA) [1], [2] is not a disease but a term that gather together all forms of arthritis which begin before the age of 16 years, persist for more than 6 weeks, and are of unknown etiology. It is, therefore, an exclusion diagnosis that includes all forms of childhood chronic arthritis of unknown cause. This heterogeneous group of disorders has been classified on clinical and laboratory features to try to identify homogeneous, mutually exclusives categories. Systemic JIA (sJIA) sets well apart from all the other forms of JIA for the presence, beside arthritis, of prominent systemic features and a marked inflammatory response. The last decade has witnessed important changes in the understanding of this disease and in its therapeutic approach [2], [3].
Section snippets
Clinical features
What characterizes sJIA [1], [2] is the presence of a quotidian, high spiking fever often associated with an evanescent, non-fixed, erythematous rash. Myalgias and abdominal pain may be intense during fever peaks. Other systemic features include hepato-splenomegaly, generalized lymphoadenopathy, and serositis. Laboratory examinations show a prominent inflammatory response characterized by leukocytosis (with neutrophilia), high erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)
Pathogenesis
Laboratory observations in the last 20 years and the therapeutic results obtained with biological agents have deeply changed our understanding of the pathogenesis of sJIA as well as its treatment. The systemic features, the marked inflammatory response, the lack of sex bias, peak age at onset, and association with autoantibodies are all consistent with what is observed in autoinflammatory diseases. Moreover, laboratory and clinical observations have shown a major pathogenic role of the innate
Treatment
In the first few weeks, during the diagnostic workup period, patients are treated with nonsteroidal anti-inflammatory drugs. Once the diagnosis is made and if symptoms persist, as is often the case, steroid therapy is indicated. Usually 2 mg/kg of prednisone has a rapid effect on symptoms and laboratory abnormalities. Treatment with prednisone does not affect disease duration or long term outcome and, in the long run, is associated with severe side effects. If a chronic steroid therapy is needed
Conclusions
There is an emerging consensus that sJIA disease should be viewed as an autoinflammatory syndrome rather than a classic auto-immune disease. This is especially true for those patients that exhibit a response to IL-1 blocking agents as spectacular as that observed in cryopyrinopathies.
It is probable that sJIA does not represent a single disease but as monogenic autoinflammatory diseases, a syndrome that represents the common final pathway of potential different causes all leading to a persistent
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