Sjogren's Syndrome

Sjögren's syndrome (SS) is a chronic autoimmune disease that is characterised by reduced lacrimal and salivary gland function resulting in dry eyes and dry mouth. It can also result in skin disease, arthritis, nephritis, cytopaenia, pneumonitis, vasculitis, peripheral neuropathy, myelopathy, and cognitive dysfunction.

Pathogenesis

Both genetic and non-genetic factors are thought to be involved. It is thought that SS occurs following an environmental trigger, likely viral (but no single virus has been implicated), in a genetically susceptible individual. The immune response involves both innate and adaptive immunity leading to autoimmunity and chronic inflammation. There is a cycle of mutual stimulation of the innate and acquired immune systems resulting in glandular injury.

The pathologic lesion is a lymphocytic infiltration of affected organs. The most frequently affected tissues are the lacrimal and salivary glands, however infiltrates can occur in extraglandular sites. Other mechanisms contribute to glandular dysfunction including antibodies to the muscarinic receptors that impair neural innervation of the gland as well as deleterious effects of cytokines on neurotransmitter release.

Specific autoantibodies are found in SS, particularly anti-Ro/SSA and anti-La/SSB in 60-80% of individuals. ANA antibodies are positive in around 90% of patients. High RF factor is also common. Autoantibodies can be found many years before the onset of SS. Autoantibodies alone are not sufficient for disease induction.