Histopathology and Molecular Pathology of Vitiligo

Vitiligo is a common skin disorder that manifests as whitish macules. There is no special geographic or sex predilection. Vitiligo is a multifactorial disorder. The various theories proposed include neutral theory, autoimmune theory, zincα2-glycoprotein theory, viral infection, intrinsic theory and melanocytorrhagy theory. However, the currently favored opinion is that there is a convergence of various theories known as the convergence theory. The basic defect is the absence of functional melanocytes from the epidermal melanin unit. This absence can be demonstrated by using special stains like Fontana-Masson, immunohistochemistry like HMB-45 and Melan-A and electron microscopy. Margins of lesions especially early lesions show inflammatory cells principally CD4+ and CD8+ T cells. The cornerstone of management in vitiligo is correct categorization of a case into stable and unstable vitiligo. This distinction is based mainly on clinical criteria. It is recommended that while evaluating biopsies, histopathological examination should be primarily concentrated on evaluating five histopathological variables—spongiosis, epidermal lymphocytes, basal cell vacuolation, dermal lymphocytes and melanophages. These parameters are then scored using a scoring system, and the recommended diagnoses based on these scores are given. Adoption of a systematic reporting system brings more consistency and objectivity in the diagnosis.