[Behçet's disease from the aspect of autoinflammatory disease]

Behçet's disease is a systemic inflammatory disease presented with recurrent oral aphtha, cutaneous manifestations, uveitis, and genital ulcer. The etiology of Behçet's disease is still unknown, but both genetic background and environmental factors are thought to be important in the pathogenesis of Behçet's disease. Behçet's disease has long been regarded as a Th1 type autoimmune disease, because of the association with HLA-B51 and hyperreactivity against streptococcal antigen. However, it was recently found that Behçet's disease and autoinflammatory diseases share several clinical features. Furthermore, increased activity of neutrophils and elevated levels of interleukin-1β are observed in both Behçet's disease and autoinflammatory diseases. The relationship between Behçet's disease and autoinflammatory diseases, especially Familial Mediterranean fever, is speculated, because both diseases are prevalent in the Mediterranean basin and treated with colchicine. Genetic researches on Behçet's disease and FMF suggest that the MEFV gene mutated in Familial Mediterranean fever is a probable susceptibility gene for Behçet's disease. Although many observations suggest that Behçet's disease might be autoinflammatory, there is evidence implying autoimmune pathogenesis of Behçet's disease. For example, some symptoms of Behçet's disease is treated with T cell suppressing agents. Recent data suggest that a novel subset of T cells, Th17, plays a crucial role in pathogenesis of Behçet's disease, and genome-wide association researches verified it. IL-17, which is the secreted from of Th17 activates neutrophils. Hence, IL-17 might cause the symptoms resembling autoinflammatory diseases. Recently, Anti-IL-1 treatment proved to be effective and other susceptibility genes are being investigated. These new findings will shed light on the long-sought pathogenesis of Behçet's disease.