|Classification and external resources|
Histopathologic image of focal lymphoid infiltration in the minor salivary gland associated with Sjögren's syndrome. Lip biopsy. H & E stain.
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Sjögren's syndrome (pronounced /ˈʃoʊɡrɨn/ SHOH-grin or /ˈʃʌrɡrɨn/ SHUR-grin in English) is a chronic autoimmune disease in which the body's white cells destroy the exocrine glands, specifically the salivary and lacrimal glands, that produce saliva and tears, respectively. The immune-mediated attack on the salivary and lacrimal glands leads to the development of dry mouth (xerostomia) and dry eyes (keratoconjunctivitis sicca), which takes place in association with lymphocytic infiltration of the glands That inflammatory process eventually severely damages or destroys the glands.
There are two types of Sjögren's syndrome, primary or secondary form. Primary Sjögren’s syndrome presents alone, in the absence of other autoimmune or connective tissue disorders and only impacts the salivary and lacrimal glands. Secondary Sjogren’s syndrome presents along with other autoimmune or connective tissue disorders, such as rheumatoid arthritis (RA) or systemic lupus erythematosus (SLE). People with secondary Sjogren's frequently continue to develop additional autoimmune disorders, such as Interstitial Cystitis.
In the United States, most of the population, as well as many medical providers, know little or nothing about Sjogren's syndrome. As the second most common form of arthritis, greater awareness and understanding is important for patients, their support system, and the medical profession. The average time to diagnosis of the syndrome is now 4.7 years. In 2014, The Sjogren's Syndrome Foundation announced a five-year goal to cut the time to diagnoses in half. 
- 1 History
- 2 Signs and symptoms
- 3 Etiology
- 4 Diagnosis
- 5 Pathogenesis
- 6 Treatment
- 7 Prognosis
- 8 Complications
- 9 Prevention
- 10 Epidemiology
- 11 Research
- 12 See also
- 13 References
- 14 External links
Johann von Mikulicz-Radecki (1850-1905) is generally credited with the first description of Sjögren’s syndrome. 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 Mikulicz established for diagnosis, often led to misdiagnosis of Mikulicz’s syndrome. Many conditions, such as tuberculosis, infections, sarcoidosis, and lymphoma present with similar conditions to those listed under Mikulicz’s 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. Sjögren introduced the term keratoconjunctivitis sicca for the symptom of dry eyes (Keratoconjunctivitis). In 1933, he published his doctoral thesis, describing 19 females, most of whom were postmenopausal and had arthritis, showing clinical and pathological manifestations of the syndrome. Sjögren clarifies that keratoconjunctivitis sicca, resulting from water deficiency, had no relation to xerophthalmia, resulting from vitamin A deficiency. Sjögren’s thesis was not well received as the Board of Examiners criticized some clinical aspects.
After extensive research and data collection, Sjögren published an essential paper in 1951, describing 80 patients with keratoconjunctivitis sicca, 50 of whom also had arthritis. His subsequent follow-up conference trips pertaining to his paper led to an international interest in Sjogren’s syndrome. The term keratoconjunctivitis sicca coined by Sjögren himself began to be identified as Sjögren’s syndrome in literature.
Signs and symptoms
The hallmark symptom of Sjögren's syndrome is a generalized dryness, typically including xerostomia (dry mouth) and keratoconjunctivitis sicca (dry eyes), part of what are known as sicca symptoms. Sicca syndrome also incorporates vaginal dryness, chronic bronchitis and lacks signs of arthritis. Sjögren's syndrome may cause skin, nose, and vaginal dryness, and may affect other organs of the body, including the kidneys, blood vessels, lungs, liver, pancreas, peripheral nervous system (distal axonal sensorimotor neuropathy) and brain. Skin dryness in some Sjögren's patients may be the result from lymphocytic infiltration into skin glands. The symptoms develop insidiously, and the diagnosis is not considered for several years because the complaints of sicca are attributed to medications, a dry environment, aging, or believed to be too insignificant to pursue.
Sjögren's syndrome is associated with increased levels in cerebrospinal fluid (CSF) of IL-1RA, an interleukin 1 antagonist. This suggests that the disease begins with increased activity in the interleukin 1 system, followed by an auto-regulatory up-regulation of IL-1RA to reduce the successful binding of interleukin 1 to its receptors. It is likely that interleukin 1 is the marker for fatigue, however, increased IL-1RA is observed in the CSF and is associated with increased fatigue through cytokine induced sickness behavior. On the other hand, Sjögren's syndrome is characterized by decreased levels of IL-1ra in saliva, which could be responsible for mouth inflammation and dryness. Patients with secondary Sjögren's syndrome also often exhibit signs and symptoms of their primary rheumatic disorders, such as SLE, Rheumatoid Arthritis or Systemic Sclerosis.
Although the cause of Sjögren’s syndrome is unknown, it is believed to be under the influence of a combination of genetic, environmental and several other factors, as is the case with many other autoimmune disorders.
The observation of high prevalence of autoimmune disorders in families of Sjögren’s syndrome is linked with a genetic predisposition to the syndrome. Studies on the polymorphisms of Human Leukocyte Antigen (HLA)-DR and HLA-DQ gene regions in Sjögren’s syndrome patients show differential susceptibility to the syndrome due to different types of the resulting autoantibody production.
Since Sjögren’s 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 that estrogen deficiency stimulates presentation of autoantigens, inducing Sjogren’s syndrome-like symptoms.
Microchimerism of fetal cells (offspring lymphoid cells in maternal circulation) may generate autoimmunity in women who have been previously 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.
Environmental (exogenous) Factors
Viral proteins, engulfed molecules, or degraded self-structures may initiate autoimmunity by molecular mimicry and increase the chances of Sjögren’s syndrome development. Epstein-Barr virus (EBV), Hepatitis C (HCV), and human T-cell leukemia virus-1 (HTLV-1) are among the most studied infectious agents in Sjögren’s 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.
Diagnosing Sjögren's syndrome is complicated by the range of symptoms a patient may manifest, and the similarity between symptoms of Sjögren's syndrome and those of other conditions. Also, patients who have symptoms of Sjögren's syndrome approach different specialities regarding their symptoms which make the diagnosis to be hard. Since the symptoms of this autoimmune disorder such as dry eyes and dry mouth are very common among people, and mostly observed from the age of 40 and above, it is often mistaken as age related, thus ignored. On the other hand, some medications can also cause symptoms that are similar to those of Sjögren's syndrome. However, the combination of several tests, which can be done in a series, can eventually lead to the diagnosis of Sjögren's syndrome
Blood tests can be done to determine if a patient has high levels of antibodies that are indicative of the condition, such as anti-nuclear antibody (ANA) and rheumatoid factor (because SS frequently occurs secondary to rheumatoid arthritis), which are associated with autoimmune diseases. Typical Sjögren's syndrome ANA patterns are SSA/Ro and SSB/La, of which SSB/La is far more specific; SSA/Ro is associated with numerous other autoimmune conditions but are often present in Sjögren's 
Rose Bengal test measures state and function of the lacrimal glands. This test includes a nontoxic dye call Rose Bengal which is placed on to the surface of the eyes. The dye’s distinctive colour help in determining the state and functioning of tear film and the rate of tear evaporation. If any distinctive colour change is observed will point towards the condition of Sjögren's syndrome, but man related diagnostic tools will be used to confirm the condition of Sjögren's syndrome.
Schirmer's test measures the production of tears: a strip of filter paper is held inside the lower eyelid for five minutes, and its wetness is then measured with a ruler. Producing less than five millilitres of liquid is usually indicative of Sjögren's syndrome. This measurement analysis vary among patients depending on other eye related conditions and medications that they are on when the test is taken. A slit-lamp examination can reveal dryness on the surface of the eye.
In case of dry mouth and dryness in oral cavity, these symptoms are caused by the reduced production of saliva from salivary glands which composed of parotid gland, submandibular gland and sublingual gland. To check the status of salivary glands and the production of saliva, salivary flow rate is performed. Here, the patient is asked to spit as much as he/she can in to a cup and the resulting saliva sample is collected and weighed. This test results can determine whether the salivary glands are functioning adequately. If not enough saliva is produced it could mean that the patient has Sjögren's syndrome. An alternative test is nonstimulated whole saliva flow collection, in which the patient spits into a test tube every minute for 15 minutes. A resultant collection of less than 1.5 mL is considered a positive result 
A lip/salivary gland biopsy can reveal lymphocytes clustered around salivary glands, and damage to these glands due to inflammation. This test involves removing a sample of tissue from the patient’s inner lip /salivary gland and examining under microscope. In addition a sialogram, a special X-ray test is performed to see if there is any blockage in the salivary gland ducts (i.e. parotid duct) and the amount of saliva that flows in to the mouth.
There is also a radiological procedure which is a reliable and accurate test for Sjögren's syndrome. A contrast agent is injected into the parotid duct, which opens from the cheek into the vestibule of the mouth opposite the neck of the upper second molar tooth. Widespread puddling of the injected contrast scattered throughout the gland indicates Sjögren's syndrome. The Revised Classification Criteria for Sjögren's Syndrome requires the presence of signs, symptoms, and lab findings. Patient-reported symptoms must include both ocular symptoms, such as daily, persistent, troublesome dry eyes for more than three months, and oral symptoms, such as needing to drink water to swallow food. Objective evidence of eye involvement relies on Schirmer's test and the Rose bengal score (or similar). Histopathology studies should show focal lymphocytic sialadenitis. Objective evidence of salivary gland involvement is tested through ultrasound examinations, the level of unstimulated whole salivary flow, a parotid sialography or salivary scintigraphy. Autoantibodies against Ro (SSA) and/or La (SSB) antigens are also expected. SS can be excluded from people with past head and neck radiation therapy, Acquired immunodeficiency syndrome (AIDS), pre-existing lymphoma, sarcoidosis, graft-versus-host disease, and use of anticholinergic drugs (since a time shorter than four times the life of the drug).
The pathogenetic mechanisms of Sjögren's syndrome have not been fully elucidated, resulting in the lack of pathophysiology knowledge of the management of this autoimmune exocrinopathy. Although the numerous factors contributing to the progression of this disease has made it difficult to find out the exact origin and cause, major advances over the past decade have contributed to a proposed set of pathogenic events that occur prior to the diagnosis of Sjogren’s syndrome.
Sjögren's Syndrome was originally proposed to be a specific, self-perpetuating immune system-mediated loss of exocrine glands, specifically acinar and ductal cells. Although this explains the more obvious symptoms, i.e. the lack of salivary and lacrimal fluid, it does not explain the more widespread systemic effects that are seen in the progression of the disease.
In the presence of a susceptible genetic background, both environmental and hormonal factors are thought to be capable of triggering the infiltration of lymphocytes, specifically CD4+ T cells, B cells and plasma cells, causing glandular dysfunction in the salivary and lacrimal glands.
The genetic locust most significantly associated with primary Sjögren's syndrome is the major histocompatibility complex/Human leukocyte antigen (MHC/HLA) region, as demonstrated by the preliminary results of the first genome-wide association study (GWAS). This GWAS included data from a discovery cohort of 395 patients of European ancestry with primary Sjögren's syndrome, and 1,975 healthy control individuals, and from a replication study that comprised 1,234 cases and 4,779 healthy controls. Associations with polymorphisms located at six independent loci were also detected; IRF5, STAT4, BLK, ILI2A, TNIP1, and CXCR5. This also suggested the activation of the innate immune system, notably through the IFN system, B-cell activation through CXCR5-directed recruitment to lymphoid follicles and B-cell receptor (BCR) activation involving Blk, and T-cell activation owing to HLA susceptibility and the IL-12-IFN-γ-axis.
Patients of different ethnic origin carry different HLA susceptibility alleles, of which, HLA-DR and HLA-DQ are involved in the pathogenesis of Sjögren's syndrome. For example, patients from Northern and Western Europe and from North American show a high prevalence of B8, DRw52, and DR3 genes. It has been shown that HLA class II alleles are associated with the presence of specific subsets of autoantibodies, rather than with the disease itself. Autoantibodies refer to the loss of B-cell tolerance leading to production of antibodies directed against diverse organ-specific and non-organ specific antigens. Association between HLA and Sjögren's syndrome is restricted to patients with anti-SSA/Ro or anti-SSB/La antibodies. Seropositivity for anti-Ro and anti-La is associated with greater severity and longer duration of disease, and findings of their high abundance from the salivary glands of Sjögren's syndrome patients suggests their imperative role in the pathogenesis of Sjögren's syndrome.
Beyond genetics, epigenetic abnormality related to DNA methylation, histone acetylation or microRNA expression probably have key roles in the pathogenesis of autoimmune diseases, including Sjögren's syndrome, though research in this area is very limited and minimal.
Environmental factors, such as glandular viral infection, could prompt epithelial cells to activate the HLA-independent innate immune system through Toll-like receptors (TLRs). Although a number of infectious, exogenous agents have been implicated in the pathogenesis of Sjogren’s, such as Epstein-Barr virus (EBV), human T-lymphotropic virus type 1, and hepatitis C virus, their association with Sjögren's appears weak. While EBV is present in the salivary glands of normal individuals, a high incidence of EBV reactivation in Sjögren's patients has been reported with increased levels of EBV DNA. This indicates viral reactivation and inability of lymphoid infiltrates to control EBV replication in Sjögren's, leading to the initiation or perpetuation of an immune response in target organs. Nonetheless, it remains to be clarified exactly how reactivation of EBV is induced in lesions of patients with Sjögren's, and which specific molecular mechanisms are involved in the process of viral reactivation.
Inflammation – Molecular Pathway
Epithelial cells in Sjögren's syndrome lesions are active participants in the induction and perpetuation of the inflammatory process. Environmental and hormonal factors, in concert with an appropriate genetic background, are believed to trigger Sjögren's, which dysregulates epithelial cells and allows aberrant homing and activation of dendritic cells (DCs), T cells, and B cells. Dendritic cells, are antigen-presenting cells (APC), which process antigen material and present it to other T cells. Following the migration of lymphocytes into the glands in response to chemokines and specific adhesion molecules, T cells interact with epithelial cells. Epithelial cells are further activated by proinflammatory cytokines (IL-1β, IFN-γ, and TNF), which are produced by adjacent T cells. The early accumulation of plasmacytoid dendritic cells in the target tissues, which produce high levels of Type 1 IFNs, seems to be important, as these cells can further dysregulate the immune response through abnormal retention of lymphocytes in the tissues and their subsequent activation. IFN-α stimulates the production of B-cell-activating factor (BAFF) by epithelial cells, DCs, and T cells. BAFF stimulates aberrant B-cell maturation, leading to the mergence of self-reactive B cells, which locally produce autoantibodies, in a germinal-centre-like structure (GC-like), which is also the location of lymphomagenesis.
Dysregulated apoptosis is believed to play a role in the pathogenesis of a variety of autoimmune diseases, though its role in Sjögren's syndrome is controversial. Both Fas and Fas ligand, are overexpressed in primary Sjögren's syndrome patients, while expression of bcl-1, which is known to downregulate apoptosis, was found to be significantly reduced in acinar and ductal epithelial cells of Sjögren's patients compared to healthy controls. In situ studies did not show increased apoptosis among glandular epithelial cells but reduced apoptosis among infiltrating mononuclear cells. Reduced apoptosis was also implicated in the accumulation of auto-reactive B-cells found in the glands. The relationship of autoantibodies expressed in Sjögren's to apoptosis is still in research.
Sex hormones seem to influence humoral and cell-mediated immune response, with estrogen being considered one of the biggest factors responsible for gender immunologic dimorphism. Various animal models have indicated a role for estrogen deficiency in Sjögren's syndrome; mice that lack aromatase (estrogen deficiency) develop a lymphoproliferative disease that resembles Sjögren's.
There is neither a known cure for Sjögren's syndrome nor a specific treatment to permanently restore gland secretion. Instead, treatment is generally symptomatic and supportive. Moisture replacement therapies such as artificial tears may ease the symptoms of dry eyes. Some patients with more severe problems use goggles to increase local humidity or have punctal plugs inserted to help retain tears on the ocular surface for a longer time. Additionally, cyclosporine (Restasis) is available by prescription to help treat chronic dry eye by suppressing the inflammation that disrupts tear secretion. Prescription drugs are also available that help to stimulate salivary flow, such as cevimeline (Evoxac) and pilocarpine. Salagen, a man-made form of pilocarpine, can be used to help produce tears as well as saliva in the mouth and intestines. It is derived from the Jaborandi plant.  In women with Sjögren's syndrome vaginal dryness is reported often and thus vaginal lubrications are recommended to avoid any irritation or pain that result from dryness in the vaginal area.
Nonsteroidal anti-inflammatory drugs may be used to treat musculoskeletal symptoms. For individuals with severe complications, corticosteroids or immunosuppressive drugs may be prescribed, and sometimes IVIG (intravenous immunoglobulin). Also, disease-modifying antirheumatic drugs (DMARDs) such as methotrexate may be helpful. Hydroxychloroquine (Plaquenil) is another option and is generally considered safer than methotrexate. However, these prescribed drugs have a range of side effects such as nausea, loss of appetite, dizziness, hair loss, stomach aches/cramps, headache, liver toxicity and increased risk of infections. Also studies have shown that patients who are on immune suppression drugs are likely to develop cancer later on.
In the advanced stage, despite the use of tear replacement drops, the eyes always feel burning, scratchy, sore. The sufferer is always aware of some discomfort; the eyes feel worse in the morning and late evening. The use of tear replacement drops becomes tedious and ineffective. At this point it may be appropriate to consider punctal plugs.
Each eye has two sites at the inner corner of each eyelid where tears drain from the eye. The upper eyelid 'puncta' drains approximately 40% of the tears away and the lower puncta drains away the remaining 60% of the tears. If there is a problem with the quantity of tears, as there is in Sjögren's disease, plugging the lower puncta can result in the tears that the patient has remaining on the eye longer.
Punctal plugs can be inserted into the lower or upper tear drainage canals of the eyes. The procedure takes only a few minutes and is painless. It can be done in the optometrist or ophthalmologist's office. Generally, collagen plugs are inserted first. These plugs will dissolve within a few days, so it gives the patient a chance to see if there is any improvement in comfort. Generally, the improvement is immediate. The patient may proceed to use of permanent plugs, although these too can be removed if necessary.
Preventive dental treatment is also necessary (and often overlooked by the patient), as the lack of saliva associated with xerostomia creates an ideal environment for the proliferation of bacteria that cause dental caries (cavities). Treatments include at-home topical fluoride application to strengthen tooth enamel and frequent teeth cleanings by a dental hygienist. Existing cavities must also be treated, as cavities that extend into the tooth can not be effectively treated through teeth cleaning alone, and are at a high risk of spreading into the pulp of the tooth, leading to the loss of vitality and need for extraction or root canal therapy. This treatment regimen is the same as that used for all xerostomia patients, such as those undergoing head and neck radiation therapy which often damages the salivary glands, as they are more susceptible to radiation than other body tissues.
Unfortunately, many patients, not realizing the need for dental treatment, do not see a dentist until most of their teeth are beyond the point of restoration. It is not uncommon for a dentist to see a xerostomia patient with severe, untreatable cavities in almost every tooth. In severe cases, the only viable treatment may be to extract all of the patient's teeth and treat with prosthetics such as dentures or implants.
Sjögren's can damage vital organs of the body with symptoms that may plateau or worsen, or go into remission as with other autoimmune diseases. Some people may experience only the mild symptoms of dry eyes and mouth, while others have symptoms of severe disease. Many patients can treat problems symptomatically. Others are forced to cope with blurred vision, constant eye discomfort, recurrent mouth infections, swollen parotid glands, hoarseness, and difficulty in swallowing and eating. Debilitating fatigue and joint pain can seriously impair quality of life. Some patients can develop renal involvement (autoimmune tubulointerstitial nephritis) leading to proteinuria, urinary concentrating defect and distal renal tubular acidosis.
Published studies on the survival of Sjögren's patients are limited in varied respects, perhaps owing to the relatively small sample sizes, and secondary sjogren’s syndrome associated to other autoimmune diseases. However, results from a number of studies indicated that compared to other autoimmune diseases, Sjögren’s is associated with a notably high incidence of malignant non-Hodgkin lymphoma (NHL). NHL is the cancer derived from white blood cells. About 5% of patients with Sjögren's syndrome will develop some form of lymphoid malignancy. Patients with severe cases are much more likely to develop lymphomas than patients with mild or moderate cases. The most common lymphomas are salivary extranodal marginal zone B cell lymphomas (MALT lymphomas in the salivary glands) and diffuse large B-cell lymphoma.
Lymphomagenesis in primary Sjögren's patients is considered as a multi-step process, with the first step being chronic stimulation of autoimmune B cells, especially B cells that produce Rheumatoid Factor (RF) at sites targeted by the disease. This increases the frequency of oncogenic mutation, leading to any dysfunction at checkpoints of autoimmune B-cell activation to transform into malignancy. A study's finding has concluded the continuous stimulation of autoimmune B cells, leading to subtle germinal abnormalities in genes having specific consequences in B cells, which underlies the susceptibility to lymphoma.
Apart from this notably higher incidence of malignant NHL, Sjögren’s patients show only modest or clinically insignificant deterioration in specific organ-related function, which explains the only slight increases in mortality rates of Sjögren’s syndrome patients in comparison with the remainder of the population.
Among the complications discussed above, Sjögren's syndrome in women who become pregnant has been linked to increased incidence of neonatal lupus erythematosus with congenital heart block requiring a pacemaker. Type I cryoglobulinemia is a known complication of Sjogren's syndrome.
There is no prevention mechanism for Sjögren's syndrome due to its complexity as an autoimmune disorder. However, lifestyle changes can reduce the risk factors of getting Sjögren's syndrome or reduce the severity of the condition with patients who have already been diagnosed. Diet is strongly associated with inflammation that is mostly seen in many autoimmune related diseases including Sjögren's syndrome. An experimental study show that Sjögren's syndrome patients show high sensitivity to gluten which directly relates to inflammation. A typical western diet is known to contain many pro-inflammatory substances that predisposes towards inflammation and autoimmune disorders, thus adequate alteration in the diet will help to reduce the risk of Sjögren's syndrome. Moderate exercise is also found be helpful in Sjögren's syndrome patients mainly reducing the effect of lung inflammation.
Sjogren’s syndrome is the second most common rheumatic autoimmune disorder, next to only rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). There are no geographical differences in the prevalence of Sjögren’s Syndrome. Sjögren's syndrome has been reported in all areas of the world, although regional epidemiology is not a thoroughly researched area. Depending on the criteria for determining prevalence, studies estimate the prevalence of Sjogren’s syndrome at 500,000 to 2 million patient in the United States. Moreover, other broader studies of prevalence of Sjögren's syndrome range widely with some reports of up to 3% of the population prevalence. Few studies that have been conducted on the incidence of Sjögren's syndrome report that the incidence of the syndrome varies between 3 and 6 per 100,000 per year.
Nine out of ten Sjögren's patients are reported to be women. In addition to prevalence in women, having a first grade relative with an autoimmune disease and previous pregnancies have been identified as epidemiological risk factors. Differences in prevalence due to race and ethnicity are unknown.
Although Sjögren's occurs in all age groups, the average age of onset is between ages 40 and 60, although experts note that up to half of all cases may be left undiagnosed or unreported. The prevalence of Sjogren’s syndrome generally increases with age.
Sjogren’s syndrome has been known to be reported in 30-50% of patient’s with rheumatoid arthritis, as well as 10-25% with systemic lupus erythematosus.
Research on multifactorial autoimmune diseases such as Sjögren's syndrome focuses on expanding the knowledge surrounding the disorder, improving diagnostic tools and finding ways to prevent, manage, and cure the disorder. The United Kingdom Primary Sjögren's Syndrome Registry, a tissue biobank of samples taken for research, supported by the Medical Research Council, UK was established in 2010.
As an autoimmune disease, susceptibility to Sjögren's syndrome is greatly influenced by the human leukocyte antigen. DQA1*05:01, DQB1*02:01, and DRB1*03:01 alleles were identified as risk factors, while DQA1*02:01, DQA1*03:01 and DQB1*05:01 alleles were found to be protective factors for the disease. The relationship between alleles and specific race was also established. HLA-DQ2 and HLA-B8 are generally found in Caucasian patients, while HLA-DR5 is related to Greek and Israeli patients. Multiple genome-wide association scans may be conducted in the future to identify key risk variants.
Viruses that can trigger the immune response of the syndrome include human T-lymphotropic virus type 1 (HTLV-1), Epstein-Barr virus (EBV), human immunodeficiency virus (HIV) and hepatitis C virus (HCV). The UK Primary Sjögren's Syndrome Registry supports clinical trials and genetic studies of Sjögren's syndrome and is open to patients wishing to participate in research studies and researchers studying the disease.
Some research showed that the lack of vitamin A and vitamin D are associated with this disease. Vitamin D deficiency was found to be related to neurological manifestations and the presence of lymphoma among patients. On the other hand, vitamin A levels were inversely associated with extra-glandular manifestations of the disease.
In 2005, an animal model of Sjögren's syndrome was developed by immunizing mice with peptides from 60 kDa Ro-antigen. Days after immunization, the salivary flow decreased. Also, lymphocyte infiltrates and salivary dysfunction were observed which were similar to the symptoms seen in human Sjögren's syndrome.
Saliva is a potential diagnostic tool of Sjögren's syndrome because the salivary component is changed after onset of the disease. With the new miniaturization technology, called ‘lab on a chip’, the diagnosis can be more convenient.
With regard to therapeutics, multiple monoclonal antibodies were under investigation in 2007. The most promising seemed to be the anti-CD20 rituximab and the anti-CD22 epratuzumab, while the anti-TNF-α and IFN-α seemed less effective.
There are well known and established people who have been diagnosed with this disorder. World champion tennis player Venus Williams has been diagnosed and said she had struggled with fatigue for years. Olympic soccer player Shannon Boxx is another notable case who suffers from Sjögren's syndrome and Lupus. 
- Benign lymphoepithelial lesion
- Keratoconjunctivitis sicca
- List of cutaneous conditions
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