Scientists are still not exactly sure what causes this disease. It may be an autoimmune disorder, meaning the body’s immune system mistakenly attacks healthy tissue with an inflammatory response. Both HLA-B5 and HLA-B51 are gene markers that are sometimes present in patients with Behçet’s disease. But there are some people who have this gene marker who don’t have Behçet’s disease. Researchers are studying other genes related to immune function and think that infections (either bacteria or a virus) may play a role in triggering the disease in some people who have genetic markers that predispose them to Behçet’s. Genetic and environmental factors are both likely factors in the development of Behçet’s disease.