Objective To detect the expression of promyelocytic leukemia(PML)gene in peripheral blood lymphocytes from patients with psoriasis vulgaris,and to investigate the relationship between PML gene and psoriasis.Methods This study included 50 patients with vulgaris psoriasis who were aged between 18 and 65 years and had never received systemic treatment,as well as 45 healthy controls.Peripheral blood samples were collected from these subjects,and lymphocytes were separated by density-gradient technique.Then,RNA was extracted from the lymphocytes by using RNAprep pure blood kit followed by real time fluorescence-based quantitative reverse transcription-PCR for the detection of PML mRNA expression.Flow cytometry was performed to quantify the expression of PML protein in the lymphocytes.Independent samples t test was carried out to compare the differences in PML expression between the patients and controls.Results The relative quantity (RQ)of PML mRNA was 14.98 ± 3.64 in peripheral blood lymphocytes from the patients,significantly higher than that in the healthy controls(5.50 ± 1.10,t =16.79,P ＜ 0.05).Similarly,a significant increment was observed in the fluorescence intensity of PML protein in peripheral blood lymphocytes from the patients compared with the healthy controls(3.13 ± 0.27 vs.2.43 ± 0.21,t =6.93,P ＜ 0.05).Conclusions PML is overexpressed at the protein and mRNA levels in peripheral blood lymphocytes from patients with psoriasis vulgaris,hinting that PML may play a certain role in the development of psoriasis.