Functional and morphological analysis of the horny layer of pityriasis alba.

The affected skin of pityriasis alba showed functional defects in both hygroscopicity and water-holding capacity detectable by water sorption-desorption test. Furthermore using skin surface biopsy technique in 5 patients, we noted that the mean area of corneocyte obtained from the affected skin of pityriasis alba was smaller and that the surface of that area showed a more prominent villous pattern than the adjacent normal skin in scanning electron microscopical observation. In this study we demonstrated the abnormalities of the horny layer in pityriasis alba, which suggest that the condition is similar to a dermatitic change and that its hypopigmentation may be due to postinflammatory mechanisms.