INTRODUCTION
Melasma is a commonly acquired hyperpigmentation disorder that most frequently occurs in women with Fitzpatrick skin types III-VI with an average onset between 20-30 years of age.1,2,3 The most commonly affected groups include Hispanic, Asian, and patients of African descent in areas with more intense UV exposure.1,4 Men can also be affected by the condition, but account for less than twenty percent.1,3 In the United States alone, over 5 million people are affected by melasma.4 The etiology is multifactorial with several known exacerbating factors including pregnancy, hormonal contraceptives, intense UV exposure, and thyroid disorders.1,4 Interestingly in a study in Argentinian women that developed melasma during pregnancy or while taking oral contraceptives, there was a 70% incidence of thyroid abnormalities.5 Less commonly, phototoxic medications, cosmetics (especially those that contain oil of bergamot as a masking fragrance), and stress have also been cited as exacerbating factors.4,6 Melasma is characterized by irregularly shaped light to dark brown macules and patches with a symmetric distribution most commonly on the malar region, chin, and forehead.1,4 Underlying hypervascularity may occur in a significant number of patients.7,8
The centrofacial pattern is the most common form of melasma that has a distribution of hyperpigmented patches on the forehead, cheeks, upper lip, and nose.4 The less common mandibular pattern of melasma is characterized by hyperpigmented patches along the mandible ramus and tends to occur later in life with women more commonly presenting in their forties.2 There is some speculation that the mandibular subtype of melasma should instead be considered a form of poikiloderma of civatte since this pattern often occurs in postmenopausal women with signs of actinic damage.4 Non-facial melasma, which is more commonly seen in postmenopausal women, has also been reported to affect the forearms and upper back.1,4,9 Increased erythema and telangiectasias suggest that there may be a vascular component to melasma while another smaller study suggests neural involvement as a possibility.1,4,7
Etiology/Pathogenesis
Melasma is a complex multifactorial condition that has a genetic predisposition. The pathogenesis is not fully understood, but increased stem cell factor, which binds the tyrosine kinase receptor, c-kit, has been shown to play a role.1,2 Alterations in Wnt signaling pathway, α-melanocyte-stimulating hormone, barrier dysfunction, increased oxidative stress, increased mast cells, and fatty acid abnormalities have also been implicated.1,2,10 Furthermore, visible light has been noted to play a role in worsening melasma. In fact, one study examined hyperpigmentation at 7 time points over two weeks and noted that darker skin types had a darker and more sustained hyperpigmentation from visible light when compared to UVA1.11 Another study showed sustained pigmentation from visible light wavelength 415 nm after less than two hours of sun exposure.2,11,12 Melasma also has a vascular component that could influence pigmentation. Specifically, vascular endothelial growth factor is an angiogenic growth factor that is the likely cause of increased vascularity within melasma patches.7
Epidemiology
Melasma is a skin condition that affects men and women of many different skin types. Prevalence of melasma ranges from 8.8% in Latina women in the United States to up to 40% of women and 20% of men in Southeast Asia.4,13 A survey of Arab-American women living in the United States found melasma to be the 5th most common skin condition affecting 14.5% of people, while another multicenter study found that African Americans were more likely to have a positive family history.4,14,15
The centrofacial pattern is the most common form of melasma that has a distribution of hyperpigmented patches on the forehead, cheeks, upper lip, and nose.4 The less common mandibular pattern of melasma is characterized by hyperpigmented patches along the mandible ramus and tends to occur later in life with women more commonly presenting in their forties.2 There is some speculation that the mandibular subtype of melasma should instead be considered a form of poikiloderma of civatte since this pattern often occurs in postmenopausal women with signs of actinic damage.4 Non-facial melasma, which is more commonly seen in postmenopausal women, has also been reported to affect the forearms and upper back.1,4,9 Increased erythema and telangiectasias suggest that there may be a vascular component to melasma while another smaller study suggests neural involvement as a possibility.1,4,7
Etiology/Pathogenesis
Melasma is a complex multifactorial condition that has a genetic predisposition. The pathogenesis is not fully understood, but increased stem cell factor, which binds the tyrosine kinase receptor, c-kit, has been shown to play a role.1,2 Alterations in Wnt signaling pathway, α-melanocyte-stimulating hormone, barrier dysfunction, increased oxidative stress, increased mast cells, and fatty acid abnormalities have also been implicated.1,2,10 Furthermore, visible light has been noted to play a role in worsening melasma. In fact, one study examined hyperpigmentation at 7 time points over two weeks and noted that darker skin types had a darker and more sustained hyperpigmentation from visible light when compared to UVA1.11 Another study showed sustained pigmentation from visible light wavelength 415 nm after less than two hours of sun exposure.2,11,12 Melasma also has a vascular component that could influence pigmentation. Specifically, vascular endothelial growth factor is an angiogenic growth factor that is the likely cause of increased vascularity within melasma patches.7
Epidemiology
Melasma is a skin condition that affects men and women of many different skin types. Prevalence of melasma ranges from 8.8% in Latina women in the United States to up to 40% of women and 20% of men in Southeast Asia.4,13 A survey of Arab-American women living in the United States found melasma to be the 5th most common skin condition affecting 14.5% of people, while another multicenter study found that African Americans were more likely to have a positive family history.4,14,15
