Post-inflammatory hypopigmentation presents as poorly defined whitening of the skin, which is irregular in outline. Often the loss of pigment is partial rather than complete. The surface is usually normal but scaling may be present if the underlying cause is scaly (such as eczema or psoriasis).
Partial loss of pigment may follow any inflammatory skin reaction but this is most noticeable in those with dark skin. Scarring conditions such as thermal burns, discoid lupus and lichen planus will cause white atrophic hypopigmented areas. Postinflammatory hypopigmentation is a recognised hazard of laser therapy.
The differential diagnosis includes:
- Vitiligo - this is normally well defined, geographic in shape and there is complete loss of pigment.
- Pityriasis versicolor - this is made up of coalescing oval/round macules which may be slightly scaly.
- Pityriasis alba - this is seen on the face of children as slightly scaly, poorly defined macules and patches. It is common in children with dark skin but is seen in Caucasians in the summer. It is assumed to be a mild form of eczema with hypopigmentation.
- Hypopigmented mycosis fungoides - a slow progressive cutaneous T-cell lymphoma.
- Naevus depigmentosus - a congenital non-progressive hypopigmented macule or patch that is stable in its relative size and distribution throughout life.
- Nummular eczema.
- Idiopathic guttate hypomelanosis - this causes widespread hypopigmented macules on the arms and legs of middle-aged women and elderly men and women.
It may be possible to make the diagnosis on clinical grounds, based on the appearance, size, site and distribution of lesions, the age of the patient and the sex of the patient. However, skin scraping for mycology and/or biopsy for histopathology may be necessary. Laser scanning microscopy may be helpful in diagnosing hypopigmentation disorders and may offer an alternative to invasive methods.
Primary Care management
Treatment of the underlying condition is the mainstay of management. With sun exposure the white areas should eventually repigment unless scarring has occurred.
Depigmentation often resolves spontaneously after weeks or months but may persist on occasion.
When to refer
Referral may be needed in cases of diagnostic difficulty.
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