Severe delayed hemolytic transfusion reaction secondary to anti-At(a)

BACKGROUND: Anti-At(a) is a rare red cell (RBC) alloantibody found in the black population. It has been described as causing one case of mild hemolytic disease of the newborn, but its ability to cause hemolytic transfusion reactions is uncertain. CASE REPORT: The patient was a 60-year-old black female with a history of three uneventful pregnancies but no transfusions. On admission, her direct and indirect antiglobulin tests were negative, total bilirubin was 0.5 mg per dL, and lactate dehydrogenase was 224 IU per L. She received nine units of compatible RBCs in the perioperative period of a hemicolectomy. Her hemoglobin rose appropriately and stabilized at 12.6 g per dL by the 6th postoperative day. By Day 10 after surgery her hemoglobin had dropped to 6.8 g per dL, and her total bilirubin and lactate dehydrogenase had risen to 1.4 mg per dL and 783 IU per L, respectively. The direct and indirect antiglobulin tests were now newly positive with strengths of 3+. A warm hemolytic autoantibody was suspected. She was transfused two units of incompatible RBCs for a rapidly falling hemoglobin and symptomatic anemia. On Day 11, the total bilirubin rose to 3.5 mg per dL, and the lactate dehydrogenase was 1154 IU per L with a hemoglobin of 7.6 g per dL. Corticosteroids were begun. Studies of serum and an acid eluate revealed anti-At(a), but no other RBC antibodies. The patient stabilized, and further transfusion was avoided. CONCLUSION: Although anti-At(a) was previously described as being of uncertain clinical significance, this patient demonstrated the ability of the antibody to cause a severe delayed hemolytic transfusion reaction.