Sjögren's syndrome is thought to be caused by an abnormal reaction of the body's immune system.
Lymphocytes are cells in the body's immune system that travel between the blood and the lymphatic system (including the spleen and lymph nodes). They protect the body from infection and cancer. In Sjögren's syndrome, these cells recognize certain tissues in the body, particularly the glands that produce tears and saliva, as "foreign" and attack them, causing inflammation, damage and other symptoms.
A person who develops Sjögren's syndrome probably inherits the risk from one or both parents and is then exposed to some type of environmental trigger (for example, a viral infection). The exact cause is not known. This means that both genetic and non-genetic factors play a role. Genome sequencing of people with Sjögren's syndrome in both the United States and Asia has added greatly to experts' understanding of the genetic factors by identifying at least five different risk-related major gene regions.