title: Acute hemolysis of transfused A2 red cells by an auto-HI antibody.
abstract: BACKGROUND
  Anti-HI is a common cold autoantibody that complicates serologic testing for underlying alloantibodies and has only rarely been associated with hemolysis. An unusual case of an acute hemolytic transfusion reaction (AHTR) due to an anti-HI autoantibody in a subgroup A1 patient transfused with A2 red blood cells (RBCs) is reported.
  
  
  METHODS
  A 56-year-old man presented to the hospital with anemia and gastrointestinal tract bleeding. His medical history was significant for congestive heart failure, obesity, and pulmonary hypertension. On admission, he was noted to have a hemoglobin level of 7.7 g per dL and therefore transfusion of RBCs was ordered. The patient was group A, D- with a reactive antibody screen due to a cold autoantibody with HI specificity. Further serologic investigation did not detect any alloantibodies. The patient was issued an electronically cross-matched group A, D- unit of RBCs. Several hours after the transfusion, he was found to be producing "Coca-cola"-colored urine with gross hemoglobinemia visible in a posttransfusion specimen, indicating an AHTR. A transfusion reaction investigation excluded mistransfusion or a missed alloantibody and instead revealed that the patient's anti-HI had a high thermal amplitude and that the implicated unit of RBCs was from the A2 subgroup. The patient subsequently tolerated transfusion of a unit of group A1 RBCs through a blood warmer without any signs or symptoms of hemolysis.
  
  
  CONCLUSIONS
  This case illustrates that anti-HI autoantibodies rarely may behave like alloantibodies and cause AHTRs. Subsequent RBC transfusion with an appropriate ABO group or subgroup through a blood warmer is well tolerated.
authors.affiliation: Blood Transfusion Service, Department of Pathology, Massachusetts General Hospital, Boston, Massachusetts 02114-2696, USA.
authors.forename: Kamran
authors.initials: K
authors.lastname: Darabi
authors.forename: Robert S
authors.initials: RS
authors.lastname: Makar
mesh_terms: D000017:ABO Blood-Group System / Q000276:immunology*; D000208:Acute Disease; D000740:Anemia / Q000628:therapy*; D000744:Anemia, Hemolytic, Autoimmune / Q000276:immunology* / Q000517:prevention & control; D001323:Autoantibodies / Q000097:blood / Q000276:immunology; D001803:Blood Transfusion / Q000295:instrumentation; D003450:Cryoglobulins / Q000276:immunology; D005260:Female; D006361:Heating / Q000295:instrumentation; D006461:Hemolysis / Q000276:immunology*; D006801:Humans; D008875:Middle Aged; D013696:Temperature; D065227:Transfusion Reaction
chemical_list: D000017:ABO Blood-Group System; D001323:Autoantibodies; D003450:Cryoglobulins; C029443:cold agglutinins