Systemic Onset Juvenile Idiopathic Arthritis - At the Borderline between Autoinflammation and Autoimmunity

Systemic onset juvenile idiopathic arthritis (SoJIA, morbus Still) is a hyperacute disease associated with a high rate of complications, some of them life-threatening (carditis, macrophage-activating syndrome). More than half of the patients will suffer from a chronic course, mostly accompanied by destructive arthritis, after the symptoms of recurrent systemic inflammation have declined. Data from basic science as well as the significant progress in treatment options point out that SoJIA is an autoinflammatory disease, at least within the acute state of the disease. In the long-term course most of the patients with SoJIA will develop the clinical picture of chronic active disease with polyarthritis (CAPA-SoJIA). In contrast to the acute phase of disease in SoJIA, CAPA-SoJIA shows all clinical and laboratory chemical signs of an autoimmune disease. A change of treatment from antiautoinflammatory to antiautoimmune medications is frequently necessary. Therapeutic options in SoJIA have been substantially improved during the past few years. This is mainly due to the merit of biologics. Fortunately, fatal outcome has become a rare event. It remains unclear whether SoJIA encompasses just one entity - being at the borderline between autoinflammation and autoimmunity, or whether this definition includes more than one disease.