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.