TRANSITION FROM SYMPTOMLESS TO LESIONAL PSORIATIC SKIN

Numerous investigations have been carried out to describe the cellular biological changes in lesional and symptomless psoriatic skin. Althou gh these studies have increased our knowledge of the pathogenesis of p soriasis, our insight into the relevance of the individual changes in the whole pathogenic process is still limited. Studies on the transiti on between symptomless and lesional skin are of importance in assessin g the pathogenic relevance of the individual aspects. In this paper, t he literature is reviewed with respect to the transitional changes; in particular, studies on changes at the margin of the psoriatic lesion and the response of the symptomless skin to standardized injury are re viewed. From the available studies it may be concluded that changes in the stroma (i.e. increased expression of tenascin and increased endot helial alkaline phosphatase activity) are early pathogenic features. T he appearance of a predominantly lymphocytic infiltrate, in particular the extravasation of Cd4+ T lymphocytes, and the suprabasal expressio n of keratin 16 are intermediary stages. Relatively late in the pathog enesis are increased recruitment of cycling epidermal nuclei, parakera tosis, decreased expression of filaggrin and premature expression of i nvolucrin. In order to discover the pathogenic relevance of molecules which might have an impact on the development of psoriasis, sequential studies during transition from symptomless to lesional skin are worth while.