Differentials
Exogenous ochronosis
SIGNS / SYMPTOMS
Skin hyperpigmentation associated with use of the bleaching agent hydroquinone. It is caused by the deposition of polymerized homogentisic acid in the skin.
Historically, this condition follows use of hydroquinone products, and distribution correlates with areas of medicine application.
Most commonly seen in people with Fitzpatrick type V or VI skin who have used hydroquinone-containing preparations of >3% concentration for months to years, and who have had significant ultraviolet light exposure without the use of photoprotection.
INVESTIGATIONS
Skin biopsy shows golden-yellow to brown deposition of pigment in the dermis.
Postinflammatory hyperpigmentation
SIGNS / SYMPTOMS
Hyperpigmentation of skin that was previously inflamed due to dermatitis.
Diagnosis is typically made on a history of erythema, pruritus, and dermatitis preceding the hyperpigmentation.
INVESTIGATIONS
Diagnosis is clinical.
Phototoxic reaction
SIGNS / SYMPTOMS
Seen in patients exposed to systemic or topical medications or cosmetics, and then ultraviolet radiation.
Disease usually begins abruptly, in contrast to melasma, which develops gradually.
INVESTIGATIONS
Diagnosis is clinical.
Riehl melanosis
SIGNS / SYMPTOMS
Facial hyperpigmented contact dermatitis due to the use of facial cosmetics.[21]
Typically distribution is patchier than classic melasma and resolves when the offending agent is discontinued.
INVESTIGATIONS
Patch testing can be done to look for reactions to components of cosmetics.
Erythema dyschromicum perstans
SIGNS / SYMPTOMS
Also called ashy dermatosis. Most frequently seen in Hispanic people and can be seen at any age.
Clinically, it presents as multiple blue-gray macules on the neck, chest, and sometimes the face.
The color and distribution, as well as the lack of association with ultraviolet light exposure, help differentiate it from melasma.[22]
INVESTIGATIONS
Skin biopsy is nonspecific, but can show some cell death at the dermal-epidermal junction, as well as pigment incontinence.[22]
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