Localised hypopigmentation

Causes

  • Vitiligo
  • Pityriasis alba
  • Pityriasis versicolor
  • Depigmented seborrhoeic keratosis
  • Idiopathic guttate hypomelanosis
  • Sarcoidosis (rare but important)
  • Mycosis fungoides (rare but important)

 

Vitiligo

  • 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.

Pityriasis alba

  • 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.

Pityriasis versicolor

  • 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)

About Dr Sarah

I'm a GP with a husband and two young children.
This entry was posted in Credits 2020, Dermatology. Bookmark the permalink.

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