The exact cause of Behçet’s disease is unknown, although there is some evidence to suggest that both genetic and environmental factors are involved.
Genetic predisposition
The genetic theory about the cause of Behçet’s disease is that certain people are born with genes that make them more vulnerable to an environmental factor that has yet to be identified, such as a virus or a specific type of bacteria.
It is thought that if the person is exposed to the environmental factor something that they have inherited in their genes may trigger a malfunction somewhere in their body. Most experts believe that the malfunction occurs in the immune system and causes the body to attack healthy tissue.
The scientific evidence for the genetic basis for Behçet’s disease lies in the fact that a large number of people who have developed the condition have a specific type of gene called HLA B51.
Recent research carried out in 2010 has also identified two other genes (IL10 and IL23R-IL12RB2) that are relatively common in people with Behçet’s disease.
Unknown environmental factor
The evidence that a possible environmental factor is involved in Behçet’s disease is that ethnic groups, who are known to be at risk of developing the condition, can reduce their risk by leaving their native country. For example, rates of Behçet’s disease among immigrant Turkish communities are significantly lower than among native Turks.
Similarly, the condition is virtually unheard of among Japanese immigrants to the United States of America despite the condition being quite widespread in Japan compared to most other countries.
Furthermore, there are a large number of cases of Behçet’s disease that develop in people who do not have any of the genes that are associated with an increased risk of developing the condition.
Possible environmental factors include:
- viral infections - such as the herpes simplex virus (HPV) - the virus that causes cold sores, the hepatitis family of viruses or parvovirus B19, which causes the childhood skin condition known as slapped cheek syndrome
- bacterial infections - such as mycobacteria which causes the lung infection tuberculosis, H. pylori which can cause stomach ulcers and streptococcal bacteria, which is a common cause of throat infections
- exposure to chemicals that are used in agricultural, such as fertilisers and pesticides
