Ultrastructure of psoriatic epidermis.

The ultrastructure of human affected and unaffected psoriatic epidermis was studied in skin biopsies from 5 patients and 3 normal controls. Transmission electron microscopic investigations revealed abnormalities in all cell layers of the affected epidermis. Common to psoriatic keratinocytes from affected epidermis was the reduction of tonofilaments. The essential ultrastructural changes were located in the stratum granulosum and stratum corneum. Thus, absence of the fusion between the keratohyalin granules and the tonofilaments was found in stratum granulosum. The keratinocytes of the stratum corneum showed a large accumulation of ribosomes and vesicles resembling lipid vesicles.