Melasma Workup

Updated: Sep 12, 2017
  • Author: Willis Hughes Lyford, ENS; Chief Editor: William D James, MD  more...
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Workup

Laboratory Studies

Usually, no laboratory tests are indicated for melasma. Some studies have suggested mild abnormalities in thyroid function are associated with melasma, specifically pregnancy- or oral contraceptive pill–associated melasma; as such, it is reasonable to consider checking thyroid function tests. Wood lamp examination usually helps to localize the pigment to the epidermis or the dermis. Note that in many cases, the pigment is found in both locations. [13]

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Histologic Findings

Melanin is increased in the epidermis, in the dermis, or (most commonly) in both locations in melasma patients. Epidermal melanin is found in keratinocytes in the basal and suprabasal area. In most cases, the number of melanocytes is not increased, yet the melanocytes that are present are larger, more dendritic, and more active. Dermal melanin is found in the superficial and mid dermis within macrophages, which often congregate around small, dilated vessels. Inflammation is sparse or absent.

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