The Control of Diseases of Tissue Reactivity by Cortisone

PATHOLOGY OF PSORIASIS. THE primary lesion is often a well defined pinhead size papule covered with fine silvery scales. The individual lesions spread at the periphery and often unite with other patches to form large plaques and sheets. Histological examination shows excessive growth of the epithelium with a badly formed horny layer (parakeratosis) and a downward growth of the interpapillary processes. As the patch enlarges healing and hyperparakeratosis occur behind the advancing periphery. There is a cellular infiltration around the papillary and subpapillary vessels and leucocytes collect between the horny cells.