Sjögren syndrome (SS) is a systemic long-term auto-immune condition which affects glands in the body's moisture-producing surfaces. Leading to dry eyes, dry mouth, dry skin, pain and fatigue. It can also strongly affect other organs, such as the lungs, kidneys, and nervous system.

Research suggest that around 0.2 > 1.2% of the global population is affected. The cause is unknown, but it has been linked to viral infections, environmental factors, and vitamin deficiencies, in combination with genetic predisposition

Glandular dysfunction is thought to arise from destruction associated with lymphocytic infiltration. The degree of glandular destruction, however, does not correlate with the severity of sicca symptoms, suggesting that other mechanisms are involved, including abnormalities in parasympathetic neurotransmission. Autoantibodies against the muscarinic acetylcholine receptor have been implicated in this process, but multiple other autoantibodies have been found.

Source : Clinical Reviews in Allergy & Immunology volume 25, pp. 89–104