By Gary M. White, MD
Brown spots after a drug eruption.
Postinflammatory hyperpigmentation (PIH) is the occurrence of dark patches of the skin at the site of a previous (recent) skin rash. It represents excess melanin in the skin caused by inflammation from the previous disorder.
It is common for the skin to darken in the areas of a prior skin condition. Some diseases are notorious for this effect, e.g. acne (in the darker-skinned patient), lichen planus, fixed drug eruption, nummular eczema and phytophotodermatitis. Single lesions can be both dark and varied in color, mimicking melanoma (see photos below).
PIH usually fades over time, but this process may take months and even years. Of course, the causative disease should be treated. Sunscreen may be applied if the area is sun-exposed. In resistant cases, hydroquinone 4% 2/day may be applied. Laser may be considered, especially the Q-switched Nd:YAG laser [JAMA Derm 2017;153;199].
Eczema (red and scaly areas) and the resulting PIH on the abdomen (buckle area) of a woman with a nickel allergy.
Same patient as in the top photo. PIH post drug eruption.
An unusually swirled pattern of PIH.
This lip pigmented lesion of several months was biopsy-proven to be postinflammatory hyperpigmentation.
PIH can be both dark and varied in color, mimicking melanoma. Both of these cases were biopsy-proven PIH.
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