Post-inflammatory hypopigmentation of skin

What is post-inflammatory hypopigmentation?

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.¹ The surface is usually normal but scaling may be present if the underlying cause is scaly (such as eczema or psoriasis).

Post-inflammatory hypopigmentation causes

Partial loss of pigment may follow any inflammatory skin reaction but this is most noticeable in those with darker skin.² Scarring conditions such as thermal burns, discoid lupus and lichen planus will cause white atrophic hypopigmented areas.¹ Post-inflammatory hypopigmentation is a recognised hazard of laser therapy.³

Differential diagnosis^{4 5}

The differential diagnosis of post-inflammatory hypopigmentation 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 on lighter skins 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.⁶

• Naevus depigmentosus - a congenital non-progressive hypopigmented macule or patch that is stable in its relative size and distribution throughout life.⁷

• Nummular eczema.⁸

• Idiopathic guttate hypomelanosis - this causes widespread hypopigmented macules on the arms and legs of middle-aged women and elderly men and women.⁹

Investigations

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.¹⁰ Laser scanning microscopy may be helpful in diagnosing post-inflammatory hypopigmentation disorders and may offer an alternative to invasive methods.¹¹

Post-inflammatory hypopigmentation treatment

Treatment of the underlying condition is the mainstay of management. With sun exposure the white areas should eventually repigment unless scarring has occurred.¹⁰ A 308 nm excimer laser has been used to stimulate pigmentation in resistant cases, but regular treatment is needed to maintained results.^{12 10}

Creams are available that can be used to camouflage the lighter patches. They are different to skin creams used for make-up because they are designed to last longer and provide heavier masking. They are available on prescription but not all local authorities will allow them to be prescribed.

Prognosis

Depigmentation often resolves spontaneously after weeks or months but may persist on occasion.⁵

When to refer

Referral may be needed in cases of diagnostic difficulty with post-inflammatory hypopigmentation.