CHAPTER 192

Pigment Disorders

Various shades and colors of human skin are created by the brown pigment, melanin. Without melanin, the skin would be pale white with varying shades of pink caused by the blood flowing through it. Fair-skinned people produce very little melanin, darker-skinned people produce moderate amounts, and very dark-skinned people produce the most. People with albinism have little or no melanin.

Melanin is produced by special cells (melanocytes) that are interspersed among the other cells in the top layer of the skin, the epidermis. After melanin is produced, it spreads into other nearby skin cells.

When exposed to sunlight, melanocytes produce increased amounts of melanin, causing the skin to darken, or tan. In some fair-skinned people, certain melanocytes produce more melanin than others in response to sunlight. This uneven melanin production results in spots of pigmentation known as freckles. A tendency to freckle runs in families. Increased amounts of melanin can be produced in response to hormonal changes, such as those that may take place in Addison’s disease, in pregnancy, or with oral contraceptive use. Some cases of skin darkening, however, are not related to increased melanin at all, but rather to abnormal pigments that make their way into the skin. Diseases such as hemochromatosis or hemosiderosis or some drugs that are applied to the skin, swallowed, or injected can cause skin darkening. A buildup of bilirubin (the main pigment in bile) causes the skin to turn yellow (jaundice).

An abnormally low amount of melanin (hypopigmentation) may affect large areas of the body or small patches. Decreased melanin usually results from a previous injury to the skin, such as a blister, ulcer, burn, or skin infection. Sometimes pigment loss results from an inflammatory condition of the skin or, in rare instances, is hereditary.

Albinism

Albinism is a rare hereditary disorder in which little or no melanin is formed.

Albinism occurs in people of all races and throughout the world.

Albinism is easily recognized by its typical appearance. People with albinism have white hair, pale skin, and pink or pale blue eyes. The genetic disorder causing albinism also results in abnormal vision and, often, in involuntary eye movements (nystagmus).

Did You Know…

Albinism occurs in people of all races.

Because melanin protects the skin from the sun, people with albinism are very prone to sunburn and skin cancer. Even a few minutes of bright sunlight can cause serious burns.

There is no cure for albinism. People with the disorder can minimize or prevent problems by doing the following:

Staying out of direct sunlight

Wearing sunglasses with UV (ultraviolet) protection and clothing that protects from the sun

Applying sunscreen that blocks UVA and UVB light with a sun protection factor (SPF) rating of at least 30 (see page 1327)

Clothing, even when it covers the body, varies in how well it protects against UV light. Generally, the tighter the weave and the heavier the weight, the more protection a fabric provides.

Vitiligo

Vitiligo is a disorder in which a localized loss of melanocytes causes patches of skin to turn white.

Patches of whitened skin are present on various parts of the body.

Doctors usually base the diagnosis on the appearance of the skin.

Corticosteroid creams or phototherapy plus light-sensitizing drugs may darken the skin, or, if needed, skin grafts may be used.

The cause of vitiligo is unknown, but it may involve an attack by the immune system on the cells that produce the skin pigment melanin (melanocytes). Vitiligo tends to run in families and may occur with certain other diseases. Vitiligo is associated with autoimmune disorders, thyroid disease being the most common. The relationship between the disorders is unclear; however, 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 sunburn.

Although vitiligo does not pose a medical problem, it may cause considerable psychologic distress.

Symptoms

In some people, one or two well-defined patches of vitiligo appear. In other people, patches appear over a large part of the body. The changes are most striking in people with dark skin. Commonly affected areas are the face, elbows, knees, hands, shins, and genitals. The affected skin is extremely prone to sunburn. The areas of skin affected by vitiligo also produce white hair because melanocytes are lost from the hair follicles.

Diagnosis

Vitiligo is recognized by its typical appearance. A Wood’s light examination is often done to help distinguish vitiligo from other causes of lightened skin (see page 1278). Other tests, including skin biopsies, are rarely necessary.

Treatment

No cure is known for vitiligo, although skin color may return spontaneously. Treatment may be helpful. Small patches sometimes darken when treated with strong corticosteroid creams. Drugs such as tacrolimus or pimecrolimus may be applied to the face, where strong corticosteroid creams may cause side effects. Some people simply use bronzers, skin stains, or makeup to darken the area. Because many people still have a few melanocytes in the patches of vitiligo, exposure to ultraviolet (UV) light in a doctor’s office (phototherapy) restimulates pigment production in more than half of them (see box on page 1294). In particular, psoralens (drugs that make the skin more sensitive to light) combined with ultraviolet A light (PUVA) or narrow-band ultraviolet B light treatment without psoralens can be given. However, phototherapy takes months to be effective and may need to 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 should be protected from the sun with clothing and sunscreen.

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.

SPOTLIGHT ON AGING

Lentigines (commonly called liver spots or age spots) are flat, tan to brown oval spots on the skin. Lentigines commonly result from spending a lot of time in the sun. They appear most frequently on areas that are exposed to the sun, such as the face and back of the hands. Lentigines that result from sun exposure are called solar lentigines. They tend to increase in number as people age. Thus, these spots are more common with advancing age. Lentigines are noncancerous, but people who have them may be at higher risk for melanoma.

Doctors can remove them with freezing treatments (cryotherapy) or laser therapy. Bleaching agents such as hydroquinone are not effective.

Some lentigines that are not related to exposure to sunlight (nonsolar lentigines) sometimes occur in people with certain rare hereditary disorders, such as Peutz-Jeghers syndrome (characterized by many lentigines on the lips and polyps in the stomach and intestine), xeroderma pigmentosum, and Leopard syndrome.

Melasma

Melasma causes dark brown patches of pigmentation to appear on sun-exposed areas, usually the face.

Melasma tends to appear during pregnancy (mask of pregnancy) and in women who take oral contraceptives, although it can occur in anyone. The disorder is most common in sunny climates and among people with darker skin.

Irregular, patchy areas of dark color appear on the skin, usually on both sides of the face. The pigmentation most often occurs in the center of the face and on the cheeks, forehead, upper lip, and nose. Sometimes people have the patches only on the sides of the face. Rarely, melasma appears on the forearms. The patches do not itch or hurt and are only of cosmetic significance.

If the skin is protected from the sun, melasma often fades after pregnancy or when an oral contraceptive is stopped. People with melasma can use sunscreens on the dark patches and avoid sun exposure to prevent the condition from getting worse. Skin-bleaching creams containing hydroquinone and retinoic acid can help lighten the dark patches.