Melasma

 

Melasma is a common hypermelanosis that typically occurs on sun-exposed areas in the face. The pathogenesis is poorly understood, but genetic and hormonal influences in combination with UV radiation are important. Specific precipitants include: birth control pills, estrogen replacement therapy, mild ovarian or thyroid dysfunction, ovarian tumors, cosmetics, nutrition, phototoxic and photoallergic medications, phototoxic drugs, and medication for epilepsy.

Melasma is rarely reported before puberty and is far more common in women, especially those of reproductive age. People with darker skin (type IV, V, or VI) are more frequently affected. The lesions are brownish macules with irregular borders and symmetric distribution in the face , often coalescing in a reticular pattern. Sun exposure intensifies the lesions. There are three major patterns of distribution of the lesions: centrofacial (63 percent: forehead, nose, chin, and upper lip), malar (21 percent: nose and cheeks), and mandibular (16 percent: ramus mandibulae). The anterior chest and dorsal forearms may also be affected.

From its appearance under Wood's lamp, melasma is classically classified into epidermal, dermal, and mixed. Clinically, the epidermal type has sharp borders, whereas the mixed or dermal type has a blotchy appearance. Epidermal pigmentation is accentuated under Wood's lamp, whereas dermal pigmentation is less apparent. In most patients, the melanin distribution is in the basal layer of the epidermis and the dermis.

Sun exposure is one of the most important causative factors, and sun protection should be included in management. Epidermal pigmentation is known to be more sensitive to topical treatment than dermal pigmentation. Hypopigmenting agents as hydroquinone, tretinoin cream, azelaic acid, rucinol, and kojic acid are helpful when used for prolonged periods. The Kligman formula is a popular combination of hydroquinone, tretinoin, and a weak topical corticoid. Chemical peels and laser therapy may be helpful in the treatment of melasma, but can also result in further unwanted hyperpigmentation. Sometimes, melasma slowly disappears after discontinuation of the hormonal stimulus and/or careful sun avoidance