What is postinflammatory hyperpigmentation?
Postinflammatory pigmentation is temporary pigmentation that follows injury (e.g. thermal burn) or inflammatory disorder of the skin (e.g. dermatitis, infection). It is mostly observed in darker skin types. Postinflammatory pigmentation is also called acquired melanosis.
More severe injury results in postinflammatory hypopigmentation, which is usually permanent.
Who gets postinflammatory pigmentation?
Postinflammatory hyperpigmentation can occur in anyone, but is more common in darker skinned individuals, in whom the colour tends to be more intense and persist for a longer period than in lighter skin colours. Pigmentation tends to more pronounced in sun-induced skin conditions such as phytophotodermatitis and lichenoid dermatoses (skin conditions related to lichen planus, such as erythema dyschromicum perstans).
Some medications may also darken postinflammatory pigmentation. These include antimalarial drugs, clofazimine, tetracycline, anticancer drugs such as bleomycin (flagellate erythema), doxorubicin, 5-fluorouracil and busulfan.
What causes postinflammatory hyperpigmentation?
Postinflammatory hyperpigmentation follows damage to the epidermis and/or dermis with deposition of melanin within the keratinocytes (skin cells) and/or dermis..
Inflammation in the epidermis stimulates melanocytes to increase melanin synthesis and to transfer the pigment to surrounding keratinocytes (epidermal melanosis). If the basal layer is injured (e.g. lichen planus), melanin pigment is released and subsequently trapped by macrophages in the papillary dermis (dermal melanosis or pigment incontinence). Dermal pigment tends to be a grey brown.
Postinflammatory pigmentation tends to become darker and more noticeable with sun exposure, so sun protection and broad-spectrum sunscreens are an important part of management. Although peeling agents may reduce epidermal pigmentation, nothing has been found useful to eradicate dermal melanosis.
What are the clinical features of postinflammatory hyperpigmentation?
Postinflammatory hyperpigmented patches are located at the site of the original disease after it has healed. The lesions range from light brown to black in colour. The patches may become darker if exposed to sunlight (UV rays).
How is postinflammatory hyperpigmentation diagnosed?
Postinflammatory hyperpigmentation is diagnosed by taking a careful history and examining the skin. Dermal melanosis gives a characteristic hue to the skin colour (grey-purple-brown).
Sometimes the diagnosis is only made after skin biopsy. Histopathology reveals patchy epidermal melanosis and/or dermal melanosis.
What is the treatment for postinflammatory hyperpigmentation?
Topical treatments for postinflammatory hyperpigmentation
A variety of topical treatments are available to lighten/bleach hyperpigmented lesions in epidermal hypermelanosis. Varying degrees of success are achieved but combinations of the treatments below are usually required for significant improvement.
- Azelaic acid
- Vitamin C cream
- Tretinoin cream
- Corticosteroid creams
- Glycolic acid peels
- Others: kojic acid, arbutin, licorice extracts, mequinol, niacinamide, N-acetyl glucosamine, soy
Physical treatments for postinflammatory hyperpigmentation
These treatments are not effective in dermal hypermelanosis.