Initial events in psoriasis: quantitative assessment*

SUMMARY Seven 3H-TdR-labelled early psoriatic lesions were quantitatively evaluated after serial sectioning and autoradiography. Epidermal thickness was measured planimetrically, whereas labelled cells as well as the number of nuclei present in the dermis were counted. Marked differences in the number of labelled cells as well as in their grain density were observed. These differences correlated with the density of the dermal infiltrate. It is concluded that psoriatic epidermal hyperplasia possibly develops as a response to antecedent and persisting events in the dermis.