Prevalence of Sjögren's syndrome in Brazilian patients infected with human T‐cell lymphotropic virus

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Excerpt

Human T‐cell lymphotropic virus type I (HTLV‐I) was the first human retrovirus to be discovered 1 and the first to be associated with pathological processes, being the etiologic agent of adult T‐cell leukemia/lymphoma 2 and of a degenerative neurological disorder known as HTLV‐I‐associated myelopathy/tropical spastic paraparesis (HAM/TSP; 3). By activating host lymphocytes, HTLV‐I causes HAM/TSP, which is a progressive chronic inflammatory condition that primarily affects the spinal cord 4. This dysregulation of the immune system results in spontaneous lymphoproliferation and increased T‐cell activation, as well as having been reported to cause several systemic changes, including, but not limited to, changes in the central nervous system (CNS; 5). In fact, HTLV‐I infection has a wide variety of manifestations.
Sjögren's syndrome (SS) is an autoimmune disorder of the exocrine glands; SS results in impaired exocrine gland function caused by progressive lymphocytic infiltration and subsequent replacement of normal glandular parenchyma with connective tissue 6. Although the etiopathogenesis of SS has yet to be fully elucidated, viral infections are believed to play an essential role in the development of the disease 7.
Some studies have shown increased viral activity in patients with HTLV‐I infection and SS 8, whereas others have shown the presence of anti‐HTLV‐I antibodies and expression of certain HTLV‐I genes and proteins in the salivary glands of patients with SS 9. On the basis of the aforementioned evidence, some authors have suggested that HTLV‐I can act as an immune‐activating pathogen for SS 8.
Epidemiological studies have found a high prevalence of seropositivity for HTLV‐I in patients with SS 8 and a high incidence of SS in patients with HTLV‐I infection 8. However, most have investigated Japanese populations 8, and Japan is highly endemic for HTLV‐I infection 13. In areas where HTLV‐I is not endemic, such as the United States, the United Kingdom, France, Spain, and South Korea, there have been no reports of increased prevalence of HTLV‐I infection in patients with SS 11.
Although South America is known to be endemic for HTLV‐I infection and Brazil has the highest absolute number of cases in the world, there is currently no epidemiological information regarding the association between HTLV‐I infection and SS in the Brazilian population. To our knowledge, only one study has examined oral manifestations of HTLV infection in patients in Brazil. The study showed that HAM/TSP was an independent risk factor for xerostomia, which was reported by 26.8% of the patients and was unrelated to the use of drugs that cause xerostomia 17. Given that xerostomia is one of the clinical signs of SS and given the reported association between SS and HTLV‐I infection, we sought to determine whether there is a relationship between the two diseases in patients in Brazil.
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