Ultrastructural studies of nuclei and nucleoli in psoriatic epidermis, compared with those in normal epidermis

Quantitative and qualitative differences of the nuclear and nucleolar structures in normal and psoriatic (involved and uninvolved) epidermis were revealed with the electron microscope. The size of nuclei and nucleoli was increased, the frequency of nuclear bodies was increased, and the relative amount of heterochromatin was decreased in involved skin compared to normal or uninvolved skin. There was no significant difference between normal skin and uninvolved skin of psoriasis. In addition to these changes, multiple fibrillar centers within nucleoli and small masses of chromatin in the epidermal nucleoplasm were observed very frequently in involved skin, while rarely or not at all in normal and uninvolved skin. These results suggest that involved psoriatic keratinocytes have increased metabolic activity and abnormal protein synthesis, having undergone gene derepression.