Journal of Mazandaran University of Medical Sciences (Jul 2024)
HLA and Eye Inflammation in Behçet\'s Syndrome
Abstract
Behçet's disease (BD) is a chronic multisystem inflammatory disorder characterized mainly by recurrent oral ulcers, ocular involvement, genital ulcers, and skin lesions, presenting with remissions and exacerbations. Arthritis, gastrointestinal lesions, vasculitis, epididymitis, and central nervous system lesions are also frequently observed disease manifestations in BD patients. This disease is more common in the Asian, Mediterranean, and China regions. The age of onset of the disease is 20 to 40 years. Eye involvement in uveitis is one of the main factors of disability caused by this disease and one of its important complications thatted to blindness. Ocular symptoms of Behcet's disease occur in 40-80% of the etiology of this disease. Ocular Behcet's manifests as uveitis (inflammation of the eye). Uveitis is a prevalent disease that mainly affects young people. It leads to a significant number of visual losses. Uveitis is a common, sight-threatening inflammatory ocular disease and includes multiple heterogeneous clinical entities. The prevalence of various types of uveitis depends upon multiple factors, such as age, sex, race, geographic distribution, environmental influence, genetics, and social habits. Epidemiologic research on uveitis is necessary to understand the etiology and immunopathogenesis of this group of diseases. The prevalence of different types of uveitis depends on several factors such as age, sex, race, geographical distribution, environmental factors, genetics, anatomical location of the inflammatory process (anterior, intermediate, posterior uveitis, pan uveitis), histopathology (granulomatous, non-granulomatous), type of inflammatory process ( acute, chronic, recurrent) and cause (infectious, non-infectious) and social habits. Common sight-threatening ocular complications of Behçet Uveitis (BU) include edema, non-perfusion, neovascularization, and atrophy of the retina and/or optic disc. Among various genetic markers, class I, HLA-B5, and its subclass B51 allele have been reported to have the strongest association with BD, but their roles in idiopathic uveitis are unclear. Many studies have confirmed the association of B*51 with uveitis. In addition to this gene, other genes also play a small role in the occurrence of the disease. BD is associated with the B51 subtype of the HLA-B5 gene, especially the B*5101 allele. The association of HLA-B51 with various manifestations of BD has been reported to be conflicting, partly due to different regional and ethnic backgrounds in various studies. HLA-B27 is the most common type of HLA in patients with uveitis, especially in the anterior uveitis, and it is mostly prognostic because it renders the patients prone to recurrent disease. Genes involved included genes expressing interleukins, chemokines, chemokine receptors, and tumor necrosis factor and genes involved in the complement system. The geographic distribution, the familial forms, and the ethnic origin of patients with Behçet's disease (BD) are many evidence in favor of a genetic background. Although BD usually occurs sporadically, familial aggregation and a higher prevalence in siblings and parents of BD patients have been observed. Although the exact pathogenesis of specific uveitis entities is not clear, accumulating evidence supports a hypothesis that uveitis is caused by an imbalanced immune response induced by an interplay of infectious, traumatic, and environmental factors in individuals with particular genetic backgrounds. In this process, the tissue-resident myeloid cells and the lymphocytes play an important role in both the initiation and the expansion of ocular inflammation.
