Hair follicle kinetics in psoriasis.

The rate of epidermal cell production has been measured in the various parts of scalp hair follicles in patients with psoriasis of the scalp, and in controls with normal scalp skin. An in vitro technique was used in which thin tissue slices were exposed to tritiated thymidine enabling cells about to divide to become autoradiographically labelled. Biopsies from thirteen patients with psoriasis and nine controls were examined in this way. The labelling indices of the interfollicular epidermis was 27-5% in the psoriatics and 9-5% in the controls. The upper part of the external root sheath had a labelling index of 28% in the psoriatic group compared to 13-9% for the controls. The labelling indices of the sebaceous glands, matrices and external root sheaths were very similar in the two groups. The findings support the hypothesis for a dermal stimulating influence causing the increased epidermopoiesis seen in psoriasis.