Development of Behçet's disease in a Caucasian with human leukocyte antigen B51 after immigration to Japan.

We herein report a 32-year-old Caucasian woman with human leukocyte antigen (HLA)-B51 who developed Behçet's disease after immigration to Japan. She was born and raised in Finland and had never experienced any clinical symptoms related to Behçet's disease before immigration to Japan. None of her family members in Finland had similar problems. Two years after the immigration, she developed typical clinical symptoms of Behçet's disease. This report strongly supports the canonical notion that the interaction of genetic factors, such as HLA-B51, with environmental factors specific to the countries in the Silk Road area, including Japan, may play a pivotal role in the pathogenesis of this disorder.