Skin Pigmentation Disorders

Disorders of Hypopigmentation

Vitiligo is a common disorder of hypopigmentation where melanocytes are destroyed. It affects approximately 1 percent of the population. There are different theories about the exact mechanism of this destruction; for example, autoimmune attacks against melanocytes may be involved. Genetics may also play a role. Treatment involves stimulating any remaining melanocytes to proliferate, and various strategies such as corticosteroids and ultraviolet light therapy are available. Commercial cosmetics may be used to dye the skin. Alternatively, individuals with extensive hypopigmentation may opt to bleach the remaining dark areas of the skin. Sun protection is important in this case to minimize the risk of future skin cancers.

Albinism is a genetic disorder involving the tyrosine kinase gene. Tyrosine kinase is an enzyme involved in the production of melanin. A defect in this enzyme means that there is no melanin production. There are several types of albinism; overall, individuals with albinism have lighter skin, hair, and eyes than is expected and are more susceptible to skin cancer. There is currently no cure for albinism, but using sun protection can help prevent skin cancer.

Hypopigmentation can also occur in systemic disorders such as tuberous sclerosis; with tinea versicolor, a superficial fungal infection; or after the skin becomes inflamed, which is called post-inflam-matory hypopigmentation. In the latter two cases, the hypopigmentation usually resolves with time once the underlying infection or inflammation has been cleared.

Disorders of Hyperpigmentation

Melasma is an acquired, benign hyperpigmentation of the face and neck. It commonly occurs with pregnancy or with the use of hormonal contraceptives. The cause is unknown, but there appears to be a genetic [Page 1555]predisposition in affected individuals. It may resolve spontaneously, but there are chemical creams that can help lighten the affected skin. As sunlight can worsen discoloration, sun protection is also recommended. Concealing agents, lasers, and chemical peels are other options.

A nevus, or a mole, is a common example of hyperpigmentation. Nevi are benign growths made of collections of melanocytes. Uncommonly, the melanocytes in nevi do not develop normally, but instead become atypical. Having many nevi with atypical melanocytes is a risk factor for malignant melanoma, the cancer of melanocytes. Nevi should be monitored for irregularities or changes and biopsied if needed.

Freckles, or ephelides, are harmless dark spots commonly seen in young, fairer individuals. They darken with sun exposure and fade without it. Sun protection will decrease exposure to the ultraviolet light that leads to increased melanin in the skin and darker freckles. Solar lentigines, or liver spots, occur after long-term sun exposure in older individuals. They do not fade or darken cyclically the way freckles do. Lasers and chemical compounds, such as hydroquinone and tretinoin, can improve the cosmetic appearance of these lesions. Inflammation of the skin can lead to hyperpigmentation, especially in individuals with darker skin. This is called post-inflammatory hyperpigmentation, and can happen after acne, eczema, or trauma. The dark lesions will eventually disappear; chemicals can again be used to hasten this process.

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