Sjogrens is a late onset chronic autoimmune disease which affects the exocrine glands, mainly the salivary and tears glands, resulting in insufficient secretion by those glands. It is characterized by a progressive lymphoid and plasma cell infiltration of the salivary and tear glands, accompanied by the production of autoantibodies (such as the anti nuclear antibodies anti-Ro/SSA and anti-La/SSB) leading to mucosal (dry mouth) and conjunctival dryness (dry eyes). Hallmarks of Sjogrens are B cell hyperactivity as manifested by hypergammaglobulinemia, circulating autoantibodies and/or immune complexes. Sjogrens may occur alone (primary Sjogrens) or secondary to other autoimmune disorders such as SLE and rheumatoid arthritis. Primary Sjogrens generally affects females (9/10 patients are female) and has an onset at age of about 40. The reasons for the female bias are unknown though hormones such as prolactin have been implicated.
Multiple genetic loci have been shown to contribute to the risk of developing Sjogrens. Of these, the HLA class II DR and DQ are the most important. An association has been demonstrated between Sjogrens and multiple HLA-DRB1, DQA1 and DQB1 alleles. Two HLA types in particular have been implicated, the DRB1*03 – DQB1*02 – DQA1*05:01 and the DRB1*15 – DQB1*06 – DQA1*01:02 haplotypes. The DRB1*03 – DQB1*02 – DQA1*05:01 haplotype has been linked to Sjogrens patients with anti- Sjogrens A and B autoantibodies while the DRB1*15 – DQB1*06 – DQA1*01:02 haplotype has been linked to Sjogrens patients with anti-Sjogrens A autoantibodies only.
Two other non HLA genes have been shown to be significantly associated with genetic susceptibility to primary Sjogrens disease, Signal Transducer and Activator of Transcription 4 (STAT4) and Interferon Regulatory Factor 5 (IRF5).
Sjogrens is diagnosed on the basis of screening questions, eye tests and salivary flow rates tests rather than on genetic testing. Genetic testing in Sjogrens may be of value in providing insights into the mechanism of the disease, thereby potentially suggesting strategies for prevention and treatment.
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