Melasma: The Daily PANCE Blueprint
A 31-year-old woman who is 5 months pregnant asks about dark patches on her face that appeared over the summer. She has symmetric, light-to-medium brown patches with irregular borders on her cheeks, upper lip, and forehead. They are flat, smooth, and not itchy, and they got darker after a beach vacation. Before this pregnancy she took a combined oral contraceptive for several years. Which is the most likely diagnosis?
A. Postinflammatory hyperpigmentation
B. Lentigo maligna
C. Melasma
D. Tinea versicolor
E. Acanthosis nigricans
Answer and topic summary
The answer is C. Melasma
Melasma causes symmetric, brown, flat patches on sun-exposed areas of the face (cheeks, forehead, upper lip, nose, and chin), driven by estrogen and UV light. That is why it appears in pregnancy (the “mask of pregnancy”), with oral contraceptives, and after sun exposure, and it is most common in women with darker skin types. A Wood lamp can help show whether the pigment sits in the epidermis or the dermis. Treatment starts with strict broad-spectrum sun protection, ideally a tinted sunscreen with iron oxides that also blocks visible light, and pregnancy-related melasma often fades after delivery. Hydroquinone and topical retinoids are avoided in pregnancy; azelaic acid is a safer choice, and triple-combination cream can be used afterward. Postinflammatory hyperpigmentation follows a prior rash or injury in its exact shape. Lentigo maligna is a single, asymmetric, slowly enlarging spot with uneven color in an older adult and needs a biopsy. Tinea versicolor has fine scale and favors the trunk. Acanthosis nigricans is velvety and thickened, in skin folds such as the neck and axillae.
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