INTRODUCTION
Melasma is a pigmentary disorder affecting over 5 million people in the United States.1 The term "melasma" is derived from the Greek root word "melas," which means black, referring to the dark, hyperpigmented macules and patches that are clinically characteristic of this condition.2 Sun-exposed areas, such as the face, are most commonly involved, particularly the bilateral cheeks, chin, and nose.2 Melasma is more prevalent in women of childbearing age, especially among those with Fitzpatrick skin types IV-VI and of Hispanic, Asian, African, or Middle Eastern descent. Prevalence ranges from 8.8% among females of Latino descent living in the southern United States, 13.4 to 15.5% in a population of Arab Americans living in southeast Michigan, and up to 40% in some females of Southeast Asian populations.3-5 In addition to the physical presentation, melasma can impact patients' quality of life, with many reporting frustration, embarrassment, and loss of confidence.6
The exact pathogenesis of melasma is complex and multifactorial, and evolving research suggests an interplay of keratinocytes, mast cells, gene regulation abnormalities, neovascularization, and basement membrane disruption.7 Common triggers include sun exposure, pregnancy, oral contraceptives, hormone replacement therapy, cosmetics, medications, and racial or genetic effects.8 Ultraviolet exposure results in an increase in melanogenic activity, leading to long-lasting epidermal pigmentation, specifically in darker skin.9-11 Hormonal influences also play a role in some individuals, given the increased prevalence of melasma during pregnancy, oral contraceptive use, and hormone therapy. Melasma occurs in 14.5% to 56% of pregnant individuals, and 11% to 46% are associated with individuals on oral contraceptives.12 During pregnancy, the increased production of pituitary hormones leads to the transcription of tyrosinase and dopachrome tautomerase, increasing pigmentation.13 In addition, estrogen and progesterone have been associated with the disease due to increased expression of estrogen and progesterone receptors on melasma-affected skin.14 Some cosmetic products have been noted to cause a phototoxic reaction, activating melasma.15 Family history is another important risk factor, with more than 30% of patients reporting a family history of melasma.8
The exact pathogenesis of melasma is complex and multifactorial, and evolving research suggests an interplay of keratinocytes, mast cells, gene regulation abnormalities, neovascularization, and basement membrane disruption.7 Common triggers include sun exposure, pregnancy, oral contraceptives, hormone replacement therapy, cosmetics, medications, and racial or genetic effects.8 Ultraviolet exposure results in an increase in melanogenic activity, leading to long-lasting epidermal pigmentation, specifically in darker skin.9-11 Hormonal influences also play a role in some individuals, given the increased prevalence of melasma during pregnancy, oral contraceptive use, and hormone therapy. Melasma occurs in 14.5% to 56% of pregnant individuals, and 11% to 46% are associated with individuals on oral contraceptives.12 During pregnancy, the increased production of pituitary hormones leads to the transcription of tyrosinase and dopachrome tautomerase, increasing pigmentation.13 In addition, estrogen and progesterone have been associated with the disease due to increased expression of estrogen and progesterone receptors on melasma-affected skin.14 Some cosmetic products have been noted to cause a phototoxic reaction, activating melasma.15 Family history is another important risk factor, with more than 30% of patients reporting a family history of melasma.8
