INTRODUCTION
Melasma is an acquired skin condition characterized by irregular brown or hyperpigmented patches typically
located on the forehead, cheeks, nose, chin and upper lip.1 It is more commonly seen in women, as well as in people with darker skin tones, particularly people of African-American, Hispanic and Asian descent.2
Melasma is the result of excess melanin deposition in the skin and can be classified into three types: epidermal, dermal and mixed corresponding to whether the increased pigment is localized
to the epidermis, dermis or a combination of the two skin layers respectively. A fourth type of melasma has also been described in individuals with skin type VI and is defined as indeterminate melasma.2 This article focuses on melasma in Latin Americans and will explore etiological influences, quality
of life issues, and provide a stepwise approach to effective therapy.
Etiology
The pathogenesis of melasma is not completely understood, but is thought to be influenced by genetics, UV exposure, thyroid dysfunction and hormonal influences from either pregnancy
or hormonal therapeutic medications.3 A study by Perez et al. proposed that idiopathic melasma (not related to pregnancy
or oral contraception) may be secondary to underlying subclinical ovarian dysfunction with potential alterations in end-organ responsiveness.4
UV exposure is likely the most influential inciting and aggravating
factor in melasma given that the condition is more common in those with darker skin types living in areas of intense radiation.
5 Melanocytes in skin affected with melasma were shown by electron microscopy to be highly dendritic, exhibit rapid increase in DNA synthesis with sun exposure and multiply rapidly.6 Sun exposure was the most frequently reported triggering
or aggravating factor in a study of 197 Tunisian patients with melasma.7
Similarly, Ortonne et al. recently conducted a survey in nine clinics worldwide and reported that 48 percent of the subjects had a family history of melasma and of those with a family history, 97 percent were in a first degree relative. They also reported that 42 percent of the respondents had the onset of their melasma after pregnancy, with 26 percent appearing pre-pregnancy and 26 percent during pregnancy. For those with an onset of melasma during pregnancy, the risk was increased in those who spent more time outdoors.8
While UV radiation has a clearer link in the development of melasma, there have also been studies that implicate visible light as a potential inciting factor. In a recent article, Mahmoud et al. developed a visible light source with minimal ultraviolet and infrared contamination and compared the effects of irradiation
with visible light or UVA on healthy volunteers with skin phototypes IV-VI and those with skin phototype II. The authors reported immediate induction of pigmentation after visible light exposure in healthy volunteers with phototypes IV-VI (n=20). This pigmentation differed from that induced by UVA in that it was initially brown, surrounded by ill-defined erythema and persistent during the two-week study period. These findings were confirmed with diffuse reflectance spectroscopy as well as histology. The volunteers in the study with phototype II skin (n=2) had no pigmentary alterations after irradiation with UVA or visible light. The results of this study and future studies of
