Published: April 2012
Normal skin color depends on melanin, hemoglobin (oxidized and reduced), and carotenoids. Melanin is the major color determinant and is responsible for variations in skin color. Pigmentary disorders typically indicate an increased amount of melanin, leading to darker color of the skin, called hypermelanosis or hyperpigmentation (Box 1). Decreased or absent pigment makes the skin appear lighter or white, known as hypomelanosis or hypopigmentation (Box 2). The disorders can be genetic or acquired.
Melasma is an acquired hypermelanosis, seen predominantly on sun-exposed areas in women. Most patients are pregnant women in whom the darkening is considered physiologic, although nonpregnant women taking oral contraceptives or estrogens can also develop melasma. Women of all ethnic groups are equally affected, but dark-skinned persons tend to be more affected. Approximately 10% of affected persons are men, thereby suggesting other causes.
Affected patients have asymptomatic brown patches symmetrically on the upper lips, cheeks, forehead, and chin. Pigmentation tends to be persistent but can fade slowly after pregnancy or after discontinuing oral contraception.
The diagnosis is usually straightforward. Biopsy shows increased pigment in the epidermis and dermis.
The use of sunscreen (SPF 30 or greater) is essential to minimize further darkening. Bleaching agents with hydroquinone (a hydroxyphenolic compound that inhibits the conversion of dopa to melanin), in concentrations of 2% to 4%, can help to minimize (lighten) the pigmentation. Alternatively, tretinoin cream and α-hydroxy acids can be effective. Mixed topical combinations of hydroquinone, tretinoin, and a fluorinated corticosteroid are particularly effective as short-term treatment. If the pigmentation is deeper (within the dermis), laser therapy combined with topical therapy is often very effective.
|Box 1 Disorders of Hypermelanosis|
|● Albright's syndrome|
|Freckles and lentigines; multiple lentigines syndrome|
|● Silver (argyria)|
|● Gold (chrysiasis)|
|● Addison's disease|
|● Melasma (pregnancy, oral contraceptives, estrogens)|
|● Chemotherapeutic (busulfan, bleomycin)|
|● Phenothiazines (chlorpromazine)|
|● Antibiotics (minocycline)|
|● Vitamin B12 deficiency|
|Box 2 Disorders of Hypomelanosis|
|Tuberous sclerosis (ash leaf macules)|
|● Phenolic compounds|
|Papulosquamous or eczematous|
|● Pityriasis alba|
|● Pityriasis versicolor|
|Idiopathic guttate hypomelanosis|
Any inflammatory condition in the skin (e.g., eczema, psoriasis), especially in dark-skinned patients, can lead to postinflammatory hyperpigmentation, a common late sequela characterized by patches of brown skin. Pigmentation follows the pattern of the initial disease, making the diagnosis straightforward in most patients.
Vitiligo is an acquired disorder of melanocytes characterized by complete loss of pigment within the skin to yield depigmented macules and patches. The disease usually begins in childhood or early adulthood and is occasionally associated with autoimmune disorders, most often thyroid disease (30% of patients have Graves’ disease or hypothyroidism), and less so pernicious anemia, Addison’s disease, diabetes mellitus, myasthenia gravis, and alopecia areata. Affected patients can have circulating autoantibodies, including antithyroglobulin, antimicrosomal antibodies, and antiparietal cell antibodies.
Vitiligo affects approximately 1% of the population and both genders equally. Approximately 30% to 40% patients have a family history of vitiligo, and disease has occurred in monozygotic twins.
Disease usually occurs in childhood or early adulthood. The depigmented patches are sharply delineated, surrounded by normal or darker skin, and are usually symmetrical. A segmental pattern occasionally occurs, usually in children. Vitiligo often follows trauma, with disease common on extensor sites, such as the hands, elbows, and knees. Another pattern is orificial, with depigmented areas surrounding orifices (nares, mouth, vagina, urethra, and anus).
Treatment of choice for limited disease is mid- to high-potency topical corticosteroids, although topical calcineurin inhibitors, such as tacrolimus or pimecrolimus, can also be very beneficial. If treatment is successful, repigmentation usually occurs within 3 to 4 months. Narrow-band ultraviolet B and PUVA (topical or systemic psoralens followed by ultraviolet [UV] A exposure) therapy twice weekly is effective treatment for extensive disease. Unresponsive areas can be camouflaged with make-up or self-tanning creams containing dihydroxyacetone. Epidermal grafting can help some patients with stable disease.
Oval (ash leaf) hypopigmented macules are the earliest cutaneous sign of tuberous sclerosis. Such light patches can occur at birth or in early infancy; they are often multiple and irregularly scattered on the body. A Wood’s light examination highlights the macules and helps to identify them in fair-skinned patients. Other cutaneous signs of tuberous sclerosis include facial angiofibromas (adenoma sebaceum), fibrous plaques on the forehead, periungual fibromas (Koenen’s tumors), and connective tissue nevi (shagreen patches). Ash leaf spots can resemble nevus depigmentosus, a single, stable, well-circumscribed hypomelanotic macule present at birth.
Idiopathic guttate hypomelanosis is a common benign acquired disorder characterized by small, well-defined, round white macules on the sun-exposed areas of the legs and forearms. The patches are usually asymptomatic and can resemble vitiligo. Women are more commonly affected. Treatment is not necessary.