By Disease Name > Pityriasis Alba

Pityriasis Alba

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a common hypomelanosis
white (alba) patches surmounted by fine “bran-like” (pityron is Greek for bran) scales
generally a disorder of young children
gradually disappears with age (self-limited)

 

clinical:

face most common in children
upper arms in young women
early lesion is erythematous, slightly scaling patch with indistinct margin
usually only see subsequent lesion
ddx:  tinea versicolor - KOH (+), rarely facial involvement

 

pathogenesis:

most feel that the initial event is a low-grade eczematous reaction
i.e. may be simply another form of post-inflammatory hypopigmentation caused by mild exczematous dermatitis

 

histology:

decreased melanocytes and melanosomes