title: Membrane autoantibodies in systemic lupus erythematosus: a case of autoimmune hemolytic anemia, antiphospholipid antibodies, and transient acquired activated protein C resistance.
abstract: BACKGROUND
  Warm autoimmune hemolytic anemia and antiphospholipid antibodies (which include lupus anticoagulants and anticardiolipin [ACL] antibodies) are associated, respectively, with approximately 10 and 40 percent of cases of systemic lupus erythematosus (SLE). This study reports a case of SLE presenting with an unusual constellation of findings that included an immunoglobulin M (IgM) cold autoantibody of high thermal amplitude, high-titer ACL antibodies, and transient acquired activated protein C resistance.
  
  
  METHODS
  A previously untransfused, nulligravid 17-year-old woman without a significant medical history presented with signs and symptoms of SLE and an extravascular hemolytic anemia. Spontaneous agglutination was noted in blood samples collected for testing. Serologic testing revealed a normal-titer, high-thermal-amplitude IgM red blood cell (RBC) autoantibody but no additional RBC antibodies in the patient's plasma. Additional testing was significant for a high-titer ACL IgM and a positive test for activated protein C resistance (a screening test for the Factor [F]V Leiden mutation), which prompted initiation of prophylactic anticoagulation. Confirmatory DNA testing for FV Leiden, however, was negative. The patient's symptoms, anemia, RBC autoagglutinins, ACL antibodies, and activated protein C resistance all resolved after 6 weeks of immunosuppression.
  
  
  CONCLUSIONS
  This case illustrates the wide range of clinical and laboratory findings that autoantibodies against cellular membranes may produce. IgM autoagglutinins of high thermal amplitude associated with a significant extravascular hemolytic anemia may be a presenting feature of SLE. Concomitant antiphospholipid antibodies may interfere with partial thromboplastin time-based tests of hypercoagulability such as that for activated protein C resistance.
authors.affiliation: Department of Pathology, Massachusetts General Hospital, Boston, Massachusetts, USA.
authors.forename: John F
authors.initials: JF
authors.lastname: Staropoli
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Van Cott
authors.forename: Robert S
authors.initials: RS
authors.lastname: Makar
mesh_terms: D020016:Activated Protein C Resistance / Q000209:etiology*; D000293:Adolescent; D000744:Anemia, Hemolytic, Autoimmune / Q000209:etiology*; D017152:Antibodies, Antiphospholipid / Q000097:blood / Q000276:immunology; D000918:Antibody Specificity; D001323:Autoantibodies / Q000097:blood* / Q000276:immunology; D003165:Complement System Proteins / Q000276:immunology; D003298:Coombs Test; D003450:Cryoglobulins / Q000276:immunology*; D004903:Erythrocyte Aggregation; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood / Q000276:immunology; D007075:Immunoglobulin M / Q000097:blood*; D008180:Lupus Erythematosus, Systemic / Q000097:blood / Q000276:immunology*; D011517:Prothrombin Time
chemical_list: D017152:Antibodies, Antiphospholipid; D001323:Autoantibodies; D003450:Cryoglobulins; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D003165:Complement System Proteins