Patients are most commonly from the Middle East, the Mediterranean region, and eastern Asia. Behcet syndrome is rare in northern Europe and Africa. The prevalence is between 80-370 per 100,000 population in Turkey, 10 per 100,000 population in Japan, and 0.6 per 100,000 population in the UK.[5]Saadoun D, Wechsler B. Behçet's disease. Orphanet J Rare Dis. 2012 Apr 12;7:20.
https://ojrd.biomedcentral.com/articles/10.1186/1750-1172-7-20
http://www.ncbi.nlm.nih.gov/pubmed/22497990?tool=bestpractice.com
In the US, the prevalence is 5.2 per 100,000 population.[8]Calamia KT, Wilson FC, Icen M, et al. Epidemiology and clinical characteristics of Behçet's disease in the US: a population-based study. Arthritis Rheum. 2009 May 15;61(5):600-4.
https://onlinelibrary.wiley.com/doi/full/10.1002/art.24423
http://www.ncbi.nlm.nih.gov/pubmed/19405011?tool=bestpractice.com
Behcet syndrome can affect any age group, but it is rare before puberty and after the sixth decade of life. It is most commonly seen in patients in their second and third decades. It is evenly distributed between men and women, but men frequently have more severe symptoms and poorer outcomes.[7]Kural-Seyahi E, Fresko I, Seyahi N, et al. The long-term mortality and morbidity of Behcet's syndrome: a 2-decade outcome survey of 387 patients followed at a dedicated center. Medicine (Baltimore). 2003 Jan;82(1):60-76.
http://www.ncbi.nlm.nih.gov/pubmed/12544711?tool=bestpractice.com
Some manifestations show regional differences. For example, gastrointestinal involvement is rare in Turkey but more common in Japan, and is seen in about 30% of patients in the US.[9]Yurdakul S, Tuzuner N, Yurdakul I, et al. Gastrointestinal involvement in Behcet's syndrome: a controlled study. Ann Rheum Dis. 1996 Mar;55(3):208-10.
http://www.ncbi.nlm.nih.gov/pubmed/8712889?tool=bestpractice.com
[10]Yazici Y, Adler NM. Clinical manifestations and ethnic background of patients with Behcet's syndrome in a US cohort. Arthritis Rheum. 2007;56(suppl):S502. Pathergy (subcutaneous skin hyperactivity to needle prick) is more common in the Middle East than in the US or northern Europe.