Vitiligo: a manifestation of apoptosis?

Vitiligo is a common cutaneous disorder that has significant biological and social consequences for those affected. It is characterized by a loss of melanocytes from the epidermis, which results in the absence of melanin, i.e. depigmentation. There are numerous hypotheses about the etiology of vitiligo, but no data to definitively prove one theory over another. It is likely that there are numerous causes for the loss of these melanocytes. One way to approach the identification of the etiology is to determine the mechanism by which the melanocytes are destroyed. The two known mechanisms for the destruction of cells are necrosis and apoptosis. One purpose of this paper is to review the extant data that might suggest which of the two mechanisms is operative against melanocytes in patients with vitiligo. The histological data, and some laboratory data, support apoptosis, rather than necrosis, as the mechanism for removal of melanocytes. Apoptosis can be induced by a variety of factors, including immune cytokines, some environmental chemicals (for example substituted hydroquinones such as monobenzone) or other molecular mechanisms. Current therapies, such as corticosteroids and ultraviolet light, do affect apoptosis in a variety of ways. Confirmation of apoptosis as a mechanism, and identification of how apoptosis is initiated to produce vitiligo, can serve as a basis for devising medications that might stop the progression of the disorder. The problem of vitiligo would be essentially solved if there was a medication that is well tolerated in children, adults and pregnant women, and that would halt the progression of the depigmentation. The study of apoptosis, mechanisms of its induction, and the ways to block apoptosis, is one possible way to find both the causes of depigmentation and medications to prevent its progression.