title: Matrix metalloproteinases in myasthenia gravis.
abstract: BACKGROUND
  Myasthenia gravis (MG) is an autoimmune disease with weakness in striated musculature due to anti-acetylcholine receptor (AChR) antibodies or muscle specific kinase at the neuromuscular junction. A subgroup of patients has periocular symptoms only; ocular MG (OMG). Matrix metalloproteinases (MMP) are increased in several autoimmune diseases, including generalized MG (GMG), and have been suggested to play a role in immune cell infiltration, basement membrane breakdown and autoimmune pathogenesis.
  
  
  METHODS
  Total levels of MMP2, MMP3 and MMP9 were measured in serum by ELISA.
  
  
  RESULTS
  The MG patients had increased serum levels of MMP2 (median values 200.7 vs. 159.7 ng/ml, p < 0.001) and MMP9 (median values 629.6 vs. 386.4 ng/ml, p < 0.001) compared to controls. A subgroup of patients had increased MMP3 concentration (p = 0.001). The differences were not dependent on presence of AChR antibodies. No difference was observed between GMG and OMG patients with regard to MMP2 (p = 0.598), MMP3 (p = 0.450) and MMP9 (p = 0.271).
  
  
  CONCLUSIONS
  The increased MMP levels in our MG patients group and the lack of dependence on anti-AChR antibodies suggest that MMP2, MMP3 and MMP9 play a role in the development of MG. The similarities between GMG and OMG support OMG as a systemic disease.
authors.affiliation: Department of Clinical Medicine, University of Bergen, Bergen, Norway. geir.helgeland@gmail.com
authors.forename: Geir
authors.initials: G
authors.lastname: Helgeland
authors.forename: Axel
authors.initials: A
authors.lastname: Petzold
authors.forename: Steven Paul
authors.initials: SP
authors.lastname: Luckman
authors.forename: Nils Erik
authors.initials: NE
authors.lastname: Gilhus
authors.forename: Gordon T
authors.initials: GT
authors.lastname: Plant
authors.forename: Fredrik Robert
authors.initials: FR
authors.lastname: Romi
mesh_terms: D001323:Autoantibodies / Q000097:blood; D001324:Autoantigens / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008297:Male; D020778:Matrix Metalloproteinase 2 / Q000097:blood*; D019278:Matrix Metalloproteinase 3 / Q000097:blood*; D020780:Matrix Metalloproteinase 9 / Q000097:blood*; D008875:Middle Aged; D009157:Myasthenia Gravis / Q000097:blood / Q000201:enzymology*; D011950:Receptors, Cholinergic / Q000276:immunology
chemical_list: D001323:Autoantibodies; D001324:Autoantigens; D011950:Receptors, Cholinergic; D019278:Matrix Metalloproteinase 3; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9