The collagenase MMP-9 constitutes a crucial element of inflammation and it is causally involved in severe tissue destruction during inflammatory conditions including inflammatory bowel disease [47], vascular disease [46], lupus erythematosus, Sjögren’s syndrome, sclerodermia, polymyositis, multiple sclerosis [48] and COPD [84]. This evidence concerns the gene MMP9 and polymyositis.