Melasma Workup

Updated: Apr 26, 2020
  • Author: Willis Hughes Lyford, MD; Chief Editor: William D James, MD  more...
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Approach Considerations

Melasma is almost invariably a clinical diagnosis and does not require any type of skin biopsy or laboratory workup. If the diagnosis is in question, ruling out other conditions based on the patient's history and physical examination should be the initial approach. 

Biopsy can be considered to confirm a diagnosis or to support a suspected diagnosis if the presentation is atypical or diagnosis is unclear.


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. [18]


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.


Imaging Studies

Not indicated