Combination of Factors?
Researchers think Sjogren's syndrome is caused by a combination of genetic and environmental factors. Several different genes appear to be involved, but scientists are not certain exactly which ones are linked to the disease since different genes seem to play a role in different people. For example:
- There is one gene that predisposes Caucasians to the disease.
- Other genes are linked to Sjogren's syndrome in people of Japanese, Chinese, and African American descent.
Simply having one of these genes will not cause a person to develop the disease, however. Some sort of trigger must activate the immune system.
Scientists think that the trigger may be a viral or bacterial infection. It might work like this:
- A person who has a Sjogren's syndrome associated gene gets a viral infection.
- The virus stimulates the immune system to act, but the gene alters the attack, sending fighter cells (lymphocytes) to the eye and mouth glands.
- Once there, the lymphocytes attack healthy cells, causing the inflammation that damages the glands and keeps them from working properly.
Fighter cells are supposed to die after their attack in a natural process called apoptosis, but in people with Sjogren's syndrome, they continue to attack, causing further damage.
Scientists think that resistance to apoptosis may be genetic. The possibility that the endocrine and nervous systems play a role is also under investigation.