Epidemiology, pathogenesis, animal models, and treatment of Sjögren's syndrome

Sjögren's syndrome is characterized by dry eyes (xerophthalmia) and dry mouth (xerostomia). Although general agreement exists about the ocular features of Sjögren's syndrome, significant controversy surrounds the classification criteria for defining the oral component. This has resulted in confusion in both the clinical and the research literature. The recent litigation involving silicone breast implants has forced clinicians to evaluate critically whether the condition of a particular patient fulfills specific diagnostic criteria for Sjögren's syndrome. Research studies have focused on potential genetic and environmental factors in the pathogenesis of Sjögren's syndrome. Studies of various ethnic populations have demonstrated an association with particular HLA-DR and -DQ alleles. However, the associated alleles are different for each ethnic group. No single environmental agent has been identified as a critical cofactor. Studies have concentrated on herpesviruses (Epstein-Barr virus and human herpesvirus type 6), hepatitis C virus, and retroviruses. Epstein-Barr virus isolated from patients has altered the ability to transform and lytically infect particular types of lymphocytes. Hepatitis C can lead to sicca symptoms, even in patients with relatively normal salivary gland biopsy findings. One report of Japanese patients indicated the presence of human T cell lymphotropic virus type I-like tax genes in the salivary biopsy specimens of a subset of patients and no gag, pol, or env sequences; this finding suggested a potential infection by a defective retrovirus. Studies on the pathogenesis have indicated that cytokines produced in the salivary gland are similar to T helper type 1 lymphocytes (interferon gamma).(ABSTRACT TRUNCATED AT 250 WORDS)