Postinflammatory hypopigmentation is the localized partial or total loss (depigmentation) of skin pigmentation that occurs after resolution of cutaneous inflammation or after skin trauma.
Postinflammatory hyperpigmentation (PIH) is similarly induced as a consequence of skin inflammation or trauma but results in darkening or hyperpigmentation of the skin.
These pigmentation changes can occur in all ages, skin colors, and sexes, but they affect patients with darker skin colors with greater frequency and severity.
The inflammatory process of these pigmentary alterations may be incited by skin conditions that induce inflammation, such as rash (eg, eczema, drug reaction), acne, bug bites, skin infection, or skin trauma (eg, procedural, mechanical, or thermal skin injury).
Although clinically benign, these pigmentary alterations can cause significant cosmetic and psychosocial distress.
Inflammation can result in an over- or underproduction of melanin in the epidermis through the effect of inflammatory mediators.
Time to resolution of these pigmentary changes is dependent on the underlying cause and severity of inflammation; it ranges from weeks to years. This is a separate diagnosis from scars, which result in persistent microstructural changes of the skin after trauma or inflammation.
What to Look For:
Asymptomatic hypopigmented, depigmented, or hyperpigmented macules or patches in the same distribution and configuration as the primary inflammatory lesions.
A history of preceding inflammatory changes to the skin helps guide this diagnosis.
Appreciation of the configuration and distribution of the pigmentary changes can help ascertain the inciting diagnosis.
A nonexhaustive differential for postinflammatory hypopigmentation includes:
- Pityriasis alba
- Progressive macular hypomelanosis
- Pityriasis versicolor
- Mycosis fungoides
- Eruptive hypomelanosis
- Chronic arsenic exposure
- Lichen striatus
A nonexhaustive differential for postinflammatory hyperpigmentation includes:
- Drug-induced hyperpigmentation
- Addison disease
- Acanthosis nigricans
- Exogenous ochronosis
- Periorbital hyperpigmentation
- Idiopathic eruptive macular hyperpigmentation
- Pityriasis versicolor
- Lichen planus pigmentosus
- Erythema dyschromicum perstans
- Pityriasis rosea
- Lichen simplex chronicus
- Phototoxic drug eruption (from minocycline, amiodarone, or chemotherapy)
- Fixed drug eruption
- Drug-induced flagellate pigmentation