A few studies have reported that the incidence of the syndrome varies between three and six per 100,000 per year.Nine out of 10 SS patients are women. In addition to prevalence in women, having a first-degree relative with an autoimmune disease and previous pregnancies have been identified as epidemiological risk factors. Despite the lower risk for men, primary SS in men tends to represent a more severe form of the disease. The role of race and ethnicity in the prevalence of the disease is unknown.Although Sjögrens syndrome occurs in all age groups, the average age of onset is between ages 40 and 60, although as many as half of all cases may be left undiagnosed or unreported. The prevalence of SS generally increases with age.Sjögrens syndrome is reported in 30-50% of people with rheumatoid arthritis and in 10-25% with systemic lupus erythematosus. History
Jan Mikulicz-Radecki (1850–1905) is generally credited with the first description of SS. In 1892, he described a 42-year-old man with enlargement of the parotid and lacrimal glands associated with a round-cell infiltrate and acinar atrophy. However, the criteria that Mikulicz established for diagnosis often led to misdiagnosis of Mikuliczs syndrome. Many conditions, such as tuberculosis, infections, sarcoidosis and lymphoma present with similar conditions to those ascribed to Mikuliczs syndrome. Nevertheless, the term "Mikulicz’s syndrome" is still used occasionally to describe the appearance of lymphocytic infiltrates on salivary-gland biopsies.In 1930, Henrik Sjögren (1899–1986), an ophthalmologist in Jönköping, Sweden, observed a patient with low secretions from the lacrimal and salivary glands.
Studies on the polymorphisms of human leukocyte antigen (HLA)-DR and HLA-DQ gene regions in Sjögrens patients show differential susceptibility to the syndrome as the result of different types of the resulting autoantibody production. Hormones
Since Sjögrens syndrome is associated with a high prevalence in women, sex hormones, especially estrogen, are believed to affect humoral and cell-mediated immune responses affecting susceptibility to the syndrome. Androgens are generally considered to prevent autoimmunity. Studies on mice models suggest estrogen deficiency stimulates presentation of autoantigens, inducing Sjögrens-like symptoms. Microchimerism
Microchimerism of fetal cells (offspring lymphoid cells in maternal circulation) may generate autoimmunity in women who have previously been pregnant. Generation of an autoimmune potential via microchimerism may lead to a switch from a silent form of autoimmunity with age-dependent decrease in self-tolerance. Environment
Viral proteins, engulfed molecules, or degraded self-structures may initiate autoimmunity by molecular mimicry and increase the chances of Sjögrens syndrome development. Epstein–Barr virus, hepatitis C, and human T-cell leukemia virus-1 are among the most studied infectious agents in Sjögrens syndrome. To date, no direct causes and effect relationship has been identified between these pathogens and the development of Sjögrens syndrome. Damaged self-structures targeted for apoptosis may be mistakenly exposed to the immune system, triggering autoimmunity in exocrine glands, which are often prone to autoimmune responses. Pathogenesis
The pathogenetic mechanisms of Sjögrens syndrome have not been fully elucidated, resulting in the lack of pathophysiology knowledge of the management of this autoimmune exocrinopathy.