Environmental factors and the geoepidemiology of juvenile idiopathic arthritis.

Juvenile idiopathic arthritis (JIA), the most common chronic rheumatic disease of childhood, is a clinically heterogeneous group of disorders characterized by chronic inflammatory arthritis. JIA is considered to be an autoimmune disease, which is a result of immune reaction caused or triggered by environmental factors such as infectious agents in a genetically susceptible host. The prevalence of JIA subtypes and different disease manifestations varies geographically. Various infectious agents have been suggested to be a trigger of JIA development. Numerous other factors, such as stressful life events and psychosociologic milieu, meteorological influence and maternal smoking, are suspected to be contributors of multicausal JIA pathogenesis. JIA is probably a basket of diseases rather than a single pathophysiological entity. Being a childhood autoimmune disease it could be viewed as an evolutional process or defect in the maturation of the immune system. Along the lines of the hygiene theory, multiple environment factors could interfere with the appearance and course of JIA, and no single causative factor could be been proven so far. Although many new data on the importance of the environment in JIA etiopathogenesis have appeared, the causal-result association between environmental factors and JIA remains complex and further studies are needed.