Melasma
Melasma is a common acquired pigmentary disorder characterized by a slowly progressive, symmetrical hypermelanosis with an irregular coloration, ranging from light brown to gray and dark brown. This variation in color depends upon which component of the skin is affected. The differentiation of pigment location is an important element to discern, as treatment of melasma involving the dermis is much more recalcitrant to therapeutic interventions. When it is difficult to distinguish epidermal from dermal involvement based solely on the appearance of the lesion, a Wood's lamp examination proves useful in all Fitzpatrick skin types except V and VI. During this exam, the lamp highlights epidermal melasma, but not dermal melasma.
Histologic studies demonstrate increased melanin in either the epidermis (basal and suprabasal layers), dermis (melanin-laden macrophages in a perivascular array in the superficial and middermis), or both. An increase in the activity of melanocytes exists, resulting in increased formation, melanization, and transfer of melanosomes to the epidermis/dermis (Ortonne et al., 2003). Multiple factors contribute to the development of melasma including UV exposure, pregnancy, hormone therapy, genetic influences, certain cosmetics, endocrine or hepatic dysfunction, and selected anti-epileptic drugs. Yet, most of the cases in men and up to one-third of the occurrences in women are idiopathic (Ortonne et al., 2003). Of the environmental sources, UV radiation is the most influential (Barankin, Silver, & Carruthers, 2002; Ortonne et al., 2003).
The importance of sun contact as a cause of melasma is evident by its exclusive presence in sun-exposed areas, particularly the face. A study of 76 Puerto Rican females with melasma demonstrated that it most commonly (63%) affects the cheeks, forehead, upper lip, nose, and chin (centrofacial pattern). Twenty-one percent of the lesions involve the cheeks and nose (malar distribution) and only 16% cover the mandible (mandibular pattern) (Sanchez et al., 1981). However, a study of 30 black patients (mainly women) with melasma revealed involvement of the malar region more frequently (73%) (Kanwar, Dhar, & Kaur, 1994; Kimbrough-Green et al., 1994). While melasma affects all races, individuals with Fitzpatrick skin type IV to VI (especially women of Hispanic, Caribbean, and Asian origin who live in areas of intense UV radiation) exhibit a higher incidence (Grimes, 1995). Also, women are much more likely to develop this disorder than their male counterparts, though men can be affected. Table 1 summarizes the characteristics of melasma.
Dermatology Nursing. 2004;16(5) © 2004 Jannetti Publications, Inc.
Cite this: Hyperpigmentation: An Overview of the Common Afflictions - Medscape - Oct 01, 2004.
