Abstract: Objective To investigate the expression levels of constitutive cyclooxygenase(COX-1)and inducible cyclooxygenase(COX-2)in progressive plaque psoriasis and their clinical significance.Methods Reverse transcription-polymerase ch ain reaction(RT-PCR)technique was applied to semi-quant itatively analyze COX-1 and COX-2mRNA expression in peripheral blood mononuclear cells(PBMC)from 30 psoriatic patients and 30 healthy controls,and the correlation between COX-1/-2 and psoriatic area and severity index(PASI)was evaluated.Results There was a significant difference o f COX-2 mRNA expression level betwee n psoriatic patients and normal controls(P<0.01),but no such difference was found reg arding COX-1 expression(P>0.05).Apositive correlation was noticed between COX-2 and PASI (r=0.68,P<0.01),but not between COX-1 and PASI.Conclusion The increased expression of COX-2 can stimulate over-production of prostaglandins and may be involved in the pathogenesis of progressive plaque psoriasis.

Key words: Psoriasis, Prostaglandin-endoperoxide synthase