In a recently published article in the April 21, 2010 New England Journal of Medicine, researchers from St. George’s University in London announced that 70% of the general population has the gene variant that causes an increased risk of vitiligo and a reduced risk for developing malignant melanoma. In their study, the researchers performed genetic tests on 1,514 patients with vitiligo and 2,813 control subjects without vitiligo. Study participants were Caucasians of European descent.
The Nature of Vitiligo
Vitiligo is an autoimmune skin disorder, or leukoderma, characterized by a loss of the skin pigment melanin. Skin exposed to the sun is most often affected. The skin in vitiligo typically develops areas with blanched or white dots, macules or patches that occasionally itch and occasionally have hyper-pigmented borders. The degree of pigmentation loss (depigmentation) in vitiligo varies in severity, ranging from mild skin blanching to severe or complete depigmentation. Unpigmented patches often occur near body orifices such as the lips, genitals, gingiva, areolas, and nipples.
Although the skin is most often affected in vitiligo, the hair, retina of the eyes, and the mucous membranes of the mouth, nose, genital and rectal tissue may also be affected. Some individuals with vitiligo may also develop premature graying or whitening of hair, including scalp hair, eyelashes, eyebrows, axillary hair, pubic hair, and beard. Some patients report an exacerbation or worsening of symptoms during periods of both physical and psychological stress, including the physical stress associated with sunburn.
Similar to most other autoimmune disorders, symptoms in vitiligo tend to wax and wane. Because vitiligo often runs a progressive course, unpigmented patches tend to spread to other areas of the body. The rate at which vitiligo spreads is variable. Most affected individuals develop several areas of depigmentation on different areas of skin, causing a generalized vitiligo pattern. Less often, individuals develop a focal pattern of vitiligo, in which one or two areas of unpigmented skin persist for many years in the absence of other skin changes.
Occasionally, affected individuals may notice patches of vitiligo on only one side of the body, which is called a segmental pattern. Segmental vitiligo usually occurs early in life and tends to spread rapidly.
Who Does Vitiligo Affect?
Although 70% of people have the gene variant that causes vitiligo, only about 2% of the world's population (40-50 million people) are reported to have vitiligo. Vitiligo occurs in all races, and it affects both sexes equally. Vitiligo is more likely to occur in people with another autoimmune condition, particularly autoimmune thyroid disease, adrenal insufficiency, alopecia areata, which causes baldness, and pernicious anemia. Studies show that 95% of individuals with vitiligo develop symptoms before age 40 with most new cases occurring in people 10-30 years of age.
Autoimmunity in Vitiligo
According to recent studies, melanocyte (cells that produce melanin) destruction is caused by a cell-mediated autoimmune response related to an increase in suppressor T cells (CD8 cells) and a decrease in helper T cells (CD4 cells) in association with the presence of a type-1 cytokine. Another line of research suggests that melanocytes are destroyed by an increased release of norepinephrine melanocytotoxin by adjacent autonomic nerve endings.
Genetic Association in Vitiligo and Its Implications
The newly discovered gene variant is involved with the immune system, which is not surprising since a genetic association with vitiligo and the immune system has previously been made. What makes the new finding exciting is its association with the TYR genetic locus, which encodes tyrosinase, the key enzyme in melanocytes, an enzyme required for melanin production. This finding opens the doors to new treatments for vitiligo and malignant melanoma. Currently, treatments for vitliigo include ultraviolet light therapies and immunosuppressant creams.
The study’s authors caution that the decreased risk of melanoma in vitiligo doesn’t mean that individuals cannot develop melanoma. They stressed that protection against sunburn is still necessary.
Elaine Moore - I'm a retired medical technologist and medical writer with more than 30 years experience working in hospital laboratories. Currently, I ...
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