Objective To screen for differentially expressed proteins in sera from patients with common types of psoriasis,and to identify plasma protein markers for psoriasis.Methods Serum samples were collected from 6 patients with progressive psoriasis vulgaris,5 patients with erythroderma psoriaticum,and 6 healthy human controls,and then pooled into 3 pools:psoriasis vulgaris pool,erythroderma psoriaticum pool and control pool.After removal of high-abundance albumin and IgG,the pooled samples were analyzed by two-dimensional electrophoresis (2-DE).An electrophoretic gel image analysis software was used to locate differentially expressed protein spots followed by peptide mass fingerprinting with matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS).The National Center for Biotechnology Information (NCBI) protein databases were then searched for the identification of differentially expressed proteins.Results All the three pooled serum samples were well seperated by 2-DE.As the gel image analysis software showed,there were 33 protein spots differentially expressed between the patients with psoriasis vulgaris and the healthy controls,17 between the patients with erythroderma psoriaticum and the healthy controls,and 26 between the patients with psoriasis vulgaris and those with erythroderma psoriaticum.Finally,14 proteins were identified as differentially expressed proteins.The patients with psoriasis vulgaris showed higher expression of complement component 3,interleukin-16,vitamin D-binding protein and α1-antitrypsin compared with the healthy controls; the patients with erythroderma psoriaticum showed increased expression of complement component 3,complement component H,α1-antitrypsin,hemopexin and haptoglobin,but decreased expression of serum amyloid protein compared with the healthy controls,as well as enhanced expression of α1-antitrypsin,complement component H,complement component 4 and haptoglobin compared with those with psoriasis vulgaris.Conclusion Differences exist in serum protein profiles between patients with psoriasis vulgaris and erythroderma psoriaticum,and healthy human controls.