Antibodies to phosphatidylethanolamine as the only antiphospholipid antibodies found in patients with unexplained thromboses

The objective of this study was to assess the interest of antiphosphatidyle thanolamine antibodies (aPE) in unexplained thrombosis (UT) defined as thro mbotic episode without any of the main autoimmune and hereditary thrombophi lic defects. Results from 98 UT were compared to those of (I) 142 patients with thrombophilia: 67 antiphospholipid syndrome (APS) and 75 hereditary he mostatic defects (HHD); (II) 110 patients without thrombosis: 60 with syste mic lupus erythematosus (SLE) and 50 with infectious diseases (ID). As comp ared to controls (100 blood donors), aPE prevalence was significantly highe r in both autoimmune contexts (APS: 43%: SLE: 40%, p <0.0001) and among non -autoimmune pathologies. only in UT (18%, p = 0.001) conversely to HHD (8%) or ID (10%), aPE prevalence in UT was not statistically different from tha t found in Primary APS (32%. p =0.076) but lower;han in Secondary APS (65%, p <0.005). In UT, aPE were mainly of IgM isotype like in Primary APS and t hey were found alone whereas in SLE they were always associated with classi cal antiphospholipid antibodies. No significant association was found betwe en any isotype of aPE and a site of thrombosis in UT as well as in APS. In conclusion, this study demonstrates an increase of the prevalence of aPE in patients with unexplained thrombosis. Thus, aPE investigation appears to b e of interest in UT and their persistent presence could define a biological variant of APS.