Description, Causes and Risk Factors:
Vogt Koyanagi Harada Syndrome (VKHS) is a rare autoimmune multisystem syndrome. The peak age of presentation is the third and fourth decade with equal sex incidence. Cases have most often been reported from Japan, North and South America and Europe with a seasonal peak during Spring and Autumn.
This syndrome is presumably viral in nature with autoimmune phenomenon that results in destruction of melanocytes especially of the uveal tract, meninges, cochlea, and epidermis. VKHS occurs in three phases namely the prodromal phase or the meningoencephalitic phase, followed a week or two later by the ophthalmic phase of bilateral uveitis (anterior and/or posterior) with auditory impairment occurrings in 50%. The spectrum of other ocular changes includes iridocyclitis, vitreitis and papillitis. During the last or the recovery phase, 80-90% develop poliosis (of brows, eyelashes and scalp), 60-70% develop vitiligo (usually symmetrical) and 50-75% have alopecia areata or diffuse hair loss.
The association of vitiligo, poliosis and ocular changes clearly differentiates this syndrome from any other. Alezzandrini's syndrome is a close differential which is commonly seen in adolescents and is characterized by unilateral impairment of vision and ipsilateral facial vitiligo. The pigmentary changes in VKHS tend to be permanent though some authors have documented clearance after chlorambucil therapy. Hearing is usually completely restored and uveitis may take a year or more to recover and in 66% visual acuity returns to normal.
The etiologic and pathogenic factors in VKH syndrome remain unclear. The clinical course of VKH syndrome with an influenzalike episode suggests a viral or postinfectious origin. Some studies invoke a possible role of Epstein-Barr virus reactivation in this disease. Although a viral cause has been proposed, no virus has been isolated or cultured from patients with VKH syndrome. Morris and Schlaegel found virus like inclusion bodies in the subretinal fluid of a patient with VKH syndrome.
Clinical and experimental data continue to support an immunologic etiology. An autoimmune reaction seems to be directed against an antigenic component shared by uveal, dermal, and meningeal melanocytes. The exact target antigen has not been identified, but possible candidates include tyrosinase- or tyrosinase-related proteins, an unidentified 75-kd protein obtained from cultured human melanoma cells (G-361), and S-100 protein. Evidence suggests that Th1 and Th17 subsets of T cells together with cytokines IL-23 (interleukin-23) and IL-17 (interleukin-17) are likely involved in the initiation and maintenence of the inflammatory process.
VKH syndrome can be associated with other autoimmune disorders such as autoimmune polyglandular syndrome, hypothyroidism, Hashimoto thyroiditis, diabetes mellitus, Guillain-Barr
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