Abstract: Objective To investigate the relation of the expressions of matrix metalloproteinase-2 （MMP-2） and -9 （MMP-9） with polymyositis/dermatomyositis （PM/DM）. Methods Blood samples were obtained from 8 patients with PM, 12 patients with DM and 10 normal human controls. Real-time quantitative RT-PCR and Western-blot were applied to examine the mRNA and protein expressions of MMP-2 and MMP-9 respectively in the peripheral blood mononuclear cells （PBMC） of these patients. Results The mRNA expression levels of MMP-2 and MMP-9 in the PBMC of patients with PM or DM were 2.41 and 1.66 folds as high as those of the normal controls, respectively; these differences were significant between the two groups . Increased expressions of MMP-2 and MMP-9 were also noted in the patients with PM or DM. Conclusion MMP-2 and MMP-9 may play a part in the development of polymyositis and dermatomyositis.

Key words: Polymyositis, Dermatomyositis, Matrix Metalloproteinases