Nucleolar ultrastructure in psoriatic skin lesions.

Keratinocytes in psoriatic skin lesions were studied to provide more information on the nucleolar ultrastructure in these cells. In contrast to normal keratinocytes, nucleoli in the keratinocytes of the uppermost layer of stratum granulosum (intermedium) of psoriatic lesions were characterized by the absence of the segregation of nucleolar components. In addition, the keratinocytes without keratohyalin of the uppermost layer of stratum intermedium of psoriatic lesions did not contain degranulated nucleoli. Such observations indicate an alteration of the maturation processes in the keratinocytes of the psoriatic skin lesions and the characteristic nucleolar changes apparently represent the morphological expression of the altered inhibition of the nucleolar (preribosomal) RNA synthesis.