- Pityriasis alba
- Pityriasis versicolor
- Depigmented seborrhoeic keratosis
- Idiopathic guttate hypomelanosis
- Sarcoidosis (rare but important)
- Mycosis fungoides (rare but important)
- Most often, but not invariably, on peripheral sites
- Repigmentation occurs in a perifollicular pattern
- Local areas can be treated with topical immunosuppression either with steroid cream or calcineurin inhibitors (tacrolimus, etc.). More widespread vitiligo can be treated with narrow-band UV phototherapy.
- Mainly in children/adolescents, especially with darker skin
- Round or oval non-scaly hypopigmented patches on face/neck/trunk, ill-defined border
- Typically better in autumn/winter
- Doesn’t need treatment; if treated, can use low-potency topical steroids, or topical calcineurin inhibitors
- Generally resolves with puberty.
- Caused by Malassezia yeasts
- Scaly macules are originally hyperpigmented and then hypopigmented (as Malassezia produces azelaic acid and this impairs melanocyte function)
Depigmented seborrhoeic keratoses
- Have same stuck-on appearance as the more usual SKs, but hypopigmented
- Don’t need treatment
Idiopathic guttate hypomelanosis
- Very common in the over-40s, gets more so with age
- Multiple discrete, circumscribed, porcelain-white macules
- Tends to favour sun-exposed sites, though not exclusively so
- Treatment not needed
Sarcoidosis or mycoides fungosis
- Main thing to look for, in both cases, is diffuse/progessive depigmentation not responding to vitiligo treatment.
- Hypopigmentation in the case of sarcoidosis occurs over granulomas in the dermis or SC tissue
- MF is a cutaneous T-cell lymphoma. Patches of hypopigmentation are typically observed on the trunk and proximal extremities, especially the buttocks and pelvic girdle; they’re round and might or might not be scaly.
- Refer for skin biopsy if either condition is expected.
(Another one from the archives: BMJ Sept 2018)