Post-inflammatory Hypopigmentation of Skin

This 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).²

Partial loss of pigment may follow any inflammatory skin reaction, but this is most noticeable in those with dark skin. Scarring conditions such as discoid lupus will cause white atrophic hypopigmented areas.

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 (slow progressive cutaneous T cell lymphoma)³
• Nevus depigmentosus (a congenital nonprogressive hypopigmented macule or patch that is stable in its relative size and distribution throughout life)
• Nummular eczema⁴
• Pityriasis alba - a common cause of facial hypopigmentation seen most often in prepubertal children
• 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 appearance, size, site, and distribution of lesions, age and sex of patient. However, skin scraping for mycology and/or biopsy for histopathology may be necessary.

There is very little that can be done although with sun exposure the white areas should eventually repigment unless scarring has occurred.

Depigmentation often resolves spontaneously, but may persistent on occasion.

Referral may be needed in cases of diagnostic difficulty.