Post-inflammatory hyperpigmentation (PIH) is common, a sequel to many types of skin and treatments. Excessive hyperpigmentation is associated with prior conditions such as skin infections, allergies, mechanical injuries, drug reactions, phototoxic reactions, trauma (e.g. burns), inflammatory diseases such as lichen planus, lupus erythematosus, and atopic dermatitis.
Post-inflammatory hyperpigmentation is also seen after treatment with a variety of electromagnetic devices, such as ultrasound, radiotherapy, laser, light-emitting diode, visible light, and microdermal grinding. Usually, post-inflammatory hyperpigmentation is most severe in diseases with epidermal basal cell involvement such as lupus erythematosus or lichen planus.
Pathophysiological mechanisms.
1, Post-inflammatory hyperpigmentation is caused by 1 of 2 mechanisms leading to epidermal or dermal hyperpigmentation. The epidermal inflammatory response (e.g., dermatitis) leads to oxidation of arachidonic acid resulting in prostaglandins, leukotrienes, and other products. These inflammatory products alter the activity of immune cells and melanocytes.
2. These inflammatory products stimulate the synthesis of melanocytes in the epidermis, leading to an increase in melanin and subsequent transfer of melanin to the surrounding keratin-forming cells. The increase and transfer of melanin granules leads to epidermal hyperpigmentation.
3, The difference is that dermal hyperpigmentation is the result of inflammation that destroys the basal cell layer, leading to melanin shedding and subsequent capture by macrophages in the dermal papillae, called pigment incontinence.
4, Fibroblast-derived melanogenic growth factor may be evident in the regulation of melanocyte function by mesenchymal-epidermal interactions.
5, Epidemiological prevalence Post-inflammatory hyperpigmentation is a common skin reaction, more commonly seen in dark-skinned populations. It is more pronounced and more severe in light-induced dermatoses and mossy skin disease species.
6. The incidence is the same for both sexes.
7, Age can occur at any age.
Medical history.
The diagnosis of post-inflammatory hyperpigmentation should be that the area in which the hyperpigmentation occurred has had a prior pathological process or injury.
Physical examination.
The location of the hyperpigmentation is dependent on the site where the previous skin inflammation occurred. The color of the lesions ranges from light brown to black. If the pigmentation is located in the epidermis it appears light brown, if the pigmentation is located in the dermis it appears dark gray or cyanotic.
Cause.
Excessive hyperpigmentation is associated with previous diseases such as skin infections, allergies, mechanical injuries, drug reactions, phototoxic reactions, trauma (e.g., burns), inflammatory diseases such as lichen planus, lupus erythematosus, and atopic dermatitis.
Post-inflammatory hyperpigmented lesions become darker after UV exposure and a variety of chemicals and medications, such as tetracycline, bleomycin, adriamycin, 5-fluorouracil, marineland, arsenic, silver, gold, antimalarial drugs, hormones, clofazimine.
Laboratory tests.
Wood’s lamp can help distinguish between post-inflammatory hyperpigmentation of the epidermis and post-inflammatory hyperpigmentation of the dermis. Epidermal lesions tend to have clearer borders under Wood’s lamp, while dermal lesions have blurred borders even under Wood’s lamp.
Ancillary tests.
If prior inflammatory skin disease is unclear or absent, a skin biopsy may be performed to rule out an underlying cause of hyperpigmentation.Fontana-Masson silver-stained melanin provides insight into the location of melanin granules in the epidermis and/or dermis.
Histopathological manifestations.
1, Post-inflammatory hyperpigmentation of the epidermis shows increased melanin in the basal layer of the epidermis, and occasionally huge melanin granules within the epidermis are seen.
2. Post-inflammatory hyperpigmentation of the dermis involves melanin in the upper dermis with an increase in melanophagic macrophages in the dermal papillae (pigment incontinence).