Vitiligo

Vitiligo is a disorder in which a localized loss of melanocytes results in smooth white patches of skin.
The cause of vitiligo is unknown, but it may involve an attack by the person's immune system on melanocytes. Vitiligo tends to run in families and may occur with certain other diseases. Thyroid disease is present in almost one third of people with vitiligo, but the relationship between the disorders is unclear. People with diabetes, Addison's disease, and pernicious anemia also are somewhat more likely to develop vitiligo. The disorder may occur after physical trauma or a sunburn. Although vitiligo does not pose a medical problem, it may cause considerable psychologic distress.

Symptoms and Diagnosis
In some people, one or two sharply demarcated patches of vitiligo appear; in others, patches appear over a large part of the body. The changes are most striking in dark-skinned people. Commonly affected areas are the face, elbows and knees, hands and feet, and genitals. The unpigmented skin is extremely prone to sunburn. The areas of skin affected by vitiligo also
produce white hair, because the melanocytes are lost from the hair follicles. Premature graying of scalp hair may occur even when the underlying skin is unaffected by vitiligo.
Vitiligo is recognized by its typical appearance. A Wood's light examination is often performed to help distinguish vitiligo from other causes of lightened skin. Other tests and biopsies are rarely necessary.

Treatment
No cure is known for vitiligo, although some people regain their color spontaneously. Treatment may be helpful. Small patches sometimes darken when treated with corticosteroid creams. Some people use bronzers, skin stains, or makeup to darken the area. Because many people still have a few melanocytes in the patches of vitiligo, phototherapy restimulates pigment production in more than half of them. In particular, psoralens (light-sensitive drugs) combined with ultraviolet A light (PUVA) and narrow-band ultraviolet B light treatments are most beneficial. However, phototherapy takes months to be effective and must be continued indefinitely.
Areas that do not respond to phototherapy may be treated with various skin-grafting techniques and even transplantation of melanocytes grown from unaffected areas of the person's skin. All affected areas of skin must be protected from the sun with sunscreen and clothing.
Some people who have very large areas of vitiligo sometimes prefer to bleach the pigment out of the unaffected skin to achieve an even color. Bleaching is done with repeated applications of hydroquinone cream to the skin for weeks to years. The effects of bleaching are irreversible.
[Merck]