title: Antiphospholipid antibodies among anti-U1-70 kDa autoantibody positive patients with mixed connective tissue disease.
abstract: OBJECTIVE
  The association between antiphospholipid antibodies (aPL) and recurrent venous and/or arterial thrombotic events, fetal loss, and thrombocytopenia in systemic lupus erythematosus (SLE) has been well documented. Such an association has not been carefully assessed in mixed connective tissue disease (MCTD). Our aim was to assess the prevalence and clinical significance of aPL in anti-U1-70 kDa autoantibody positive patients with MCTD.
  
  
  METHODS
  We compared 48 consecutive anti-U1-70 kDa autoantibody positive patients with MCTD versus 59 consecutive anti-U1-70 kDa autoantibody negative patients with SLE to determine the frequency of aPL and clinical features of the aPL syndrome.
  
  
  RESULTS
  Among the patients with MCTD 7/48 (15%) had anticardiolipin antibodies (aCL) versus 24/59 (41%) patients with SLE (p < 0.005) and versus 2/150 (1%) apparently healthy blood donors (p < 0.001). Among patients with MCTD with aPL, 2 were IgG, 3 IgM, and 2 both IgG and IgM isotypes; among patients with SLE 5 were IgG, 11 IgM, and 8 both IgG and IgM isotypes. No clotting events or other features of the aPL syndrome were found among the patients with MCTD compared with 26 events documented among the group of aCL positive patients with SLE (p < 0.001). There were 10 patients with SLE with deep vein thrombosis, one with a pulmonary embolism, 2 with recurrent fetal loss, one with chorea, 2 with livedo reticularis, one with severe thrombocytopenia, and one with avascular necrosis.
  
  
  CONCLUSIONS
  aCL were increased in patients with MCTD compared to controls. Furthermore, aCL were increased in SLE compared with both patients with MCTD and controls. Finally, while clotting events and other manifestations of the aPL syndrome occurred among the group of aCL positive patients with SLE these were distinctly absent from the aCL positive MCTD group.
authors.affiliation: Department of Internal Medicine, University of Missouri, Columbia 65212, USA.
authors.forename: G R
authors.initials: GR
authors.lastname: Komatireddy
authors.forename: G S
authors.initials: GS
authors.lastname: Wang
authors.forename: G C
authors.initials: GC
authors.lastname: Sharp
authors.forename: R W
authors.initials: RW
authors.lastname: Hoffman
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D017153:Antibodies, Anticardiolipin / Q000032:analysis*; D016736:Antiphospholipid Syndrome / Q000150:complications / Q000276:immunology; D001323:Autoantibodies / Q000276:immunology*; D001324:Autoantigens / Q000276:immunology; D003710:Demography; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000150:complications / Q000276:immunology*; D008875:Middle Aged; D008947:Mixed Connective Tissue Disease / Q000150:complications / Q000276:immunology*; D008970:Molecular Weight; D017412:Ribonucleoprotein, U1 Small Nuclear / Q000276:immunology*
chemical_list: D017153:Antibodies, Anticardiolipin; D001323:Autoantibodies; D001324:Autoantigens; D017412:Ribonucleoprotein, U1 Small Nuclear