The hair root pattern in psoriasis of the scalp.

Several reports suggest that a localized effluvium of scalp hair may occur in patients with psoriasis. The percentages of telogen and catagen hair have been claimed to be normal or increased in isolated cases. In the present study the anagen/telogen ratio was quantified under standardized conditions in psoriatic plaques and uninvolved areas of the scalp in 22 patients and the scalp of 22 normal controls. This assessment was carried out by light microscopic analysis of hair roots, obtained by the hair pluck-method. A consistent increase in the percentages of telogen and catagen hair was shown in psoriatic plaques, compared with the uninvolved areas. Compared with the scalp of normal controls, this percentage was significantly increased in psoriatic plaques, but not in the uninvolved areas.