**1. Introduction**

Behçet's disease (BD; MIM 109650) is an autoinflammatory disease characterized by with recurrent oral aphthae, genital ulcers and vasculitis involving the skin, joints, eyes, veins, arteries, nervous and gastrointestinal systems [1]. BD is diagnosed worldwide, although its highest prevalence coincides with the countries stretching from Japan to the Mediterranean region along the ancient trading route "Silk Route". Among the affected countries, the prevalence of BD varies between Western (0.12–7.5 per 100,000) and Eastern countries (6.3–14 per 100,000) [2]. The prevalence of BD is the highest in Turkey (80–420 cases per 100,000) [3]. Although the pathogenesis remains uncertain, it is thought that both genetic and environmental factors contribute to the onset and progression of the BD [4]. The first reported susceptibility genetic region for BD was found in the human leukocyte antigen (HLA) region, or the major histocompatibility complex (MHC) on chromosome [5]. HLA-B51 antigen was recognized as the strongest evidence of a BD genetic background [6]. Multiple other putative genes outside the HLA region have also been identified.
