RESPONSE OF THE CLINICALLY UNINVOLVED SKIN OF PSORIATIC PATIENTS TO TAPE STRIPPING DURING ACITRETIN TREATMENT

The aromatic retinoids etretinate and acitretin are widely used in the systemic treatment of severe psoriasis. The purpose of the present in vestigation was to further elucidate the mode of action of acitretin o n abnormal keratinization and epidermal hyperproliferation in an in vi vo model. Studies on the interference of acitretin with epidermal hype rproliferation and abnormal keratinization in psoriatic plaques are di fficult to interpret, as acitretin-induced changes might be due to dir ect effects of acitretin or be the indirect effect of retinoid-induced modulation of cutaneous inflammation. Using an immunohistochemical as sessment, we examined the in vivo effect of systemic acitretin (>35 mg daily) on the expression of filaggrin, involucrin, and on the recruit ment of cycling epidermal cells, in the tape-stripped uninvolved skin of psoriatic patients, a model which provides the opportunity to study epidermal regeneration in the absence of significant accumulation of T-lymphocytes. During acitretin therapy and 3 weeks after withdrawal o f acitretin, we took biopsies from uninvolved skin following tape-stri pping in 6 patients with psoriasis. Six patients with psoriasis who ha d never used acitretin served as controls. We did not observe a Koebne r response in our patients after tape stripping. Filaggrin expression was decreased, while the recruitment of cycling epidermal cells and th e involucrin expression were increased in the biopsies taken from pati ents who did not use acitretin. During acitretin treatment, however, t he filaggrin expression was similar, whereas the Ki-67 positive nuclei and the involucrin expression showed a statistically significant decr ease compared to those parameters in the patients who did not use acit retin. Our findings indicate that epidermal hyperproliferation and abn ormal keratinization are modulated directly by acitretin.