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Acquired hyperpigmentation disorders of the skin are among the most common complaints in a general dermatology clinic, especially in patients with skin of color. Among those, melasma is known both for causing significant psychosocial stress and for its difficulty to treat. Melasma is classically characterized by symmetric facial hyperpigmented macules and patches commonly affecting the forehead, malar eminences, periorbital areas, and the upper lip. Despite the advent of powerful pigment-targeting lasers, the treatment for melasma remains challenging. This chapter reviews what is currently understood about the pathogenesis, discusses evidence-based treatments, and offers clinical pearls on difficult-to-treat cases.
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In the United States alone, approximately 5 to 6 million individuals are afflicted with melasma, with a higher incidence worldwide. In Asia, it is a common diagnosis in any dermatology clinic and can reach an incidence of 0.25% to 4% of cases seen in any dermatology institution.1 Melasma is much more commonly seen in women, although men can also be affected (reported 10%),2 suggesting a hormone-related etiology. This strong linkage between melasma and hormones is demonstrated by an increased incidence in the setting of pregnancy, in which case melasma can also be termed chloasma, or “the mask of pregnancy.” In addition, the use of birth control pills or estrogen replacement therapy, ovarian or thyroid dysfunction, and ovarian tumors have also been associated with the onset of melasma.
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Although all skin types can be affected, melasma is seen at a much higher incidence in darker skin phototypes (Fitzpatrick Skin Phototypes IV to VI) with extensive ultraviolet radiation (UV) exposure. This in combination with the appearance of melasma in sun-exposed areas and the presence of solar elastosis on histology all point to a UV-mediated process.
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Medications and other systemic illnesses have also been reported to be associated with the onset of melasma, including phototoxic and photoallergic medications, antiepileptic medications, cosmetics, altered nutrition, and hepatic disease.1
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CLINICAL PRESENTATION
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Onset of melasma typically occurs in a woman's childbearing years (20s through 30s). The appearance of pigment is heightened in the summer when UV exposure is more common.
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At least three clinical patterns have been described: centrofacial (64%), malar (27%), and mandibular (9%). The course is typically chronic, fading when UV exposure is diminished.
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From a treatment standpoint, determining the distribution of pigment in the skin layers is critical. Increased pigment can be seen in either the epidermis (presenting as a brown-to-black pigment) or dermis (presenting as a blue-gray pigment), or both. A Wood's lamp (365 nm) can be useful in separating the types of pigmentation: increased reflectance will be seen in epidermal hyperpigmentation versus none in dermal hyperpigmentation. In one study of 210 patients, using a Wood's lamp, melasma was classified into epidermal (70%), dermal (10% to 15%), and mixed (20%).3 The presence of dermal ...