Detection of anti-B antibodies in a patient with A1B blood group: A case report and literature review.

ABO antibodies occur naturally and usually exist as alloantibodies. They are the most clinically significant in cases of transfusions. However, there are very few reports on auto-anti-A or B. A 58-year-old man visited our hospital for evaluation of an inguinal mass. Blood typing was performed, while preparing the patient for an excisional biopsy. Forward and reverse typing showed a typical AB and A pattern. Results of the direct antiglobulin and unexpected antibody screening tests were negative. The serum did not react with AB3 cells. The biopsy revealed a diffuse large B-cell lymphoma. After completing four cycles of R-CHOP chemotherapy, the patient achieved complete remission. There were no anti-B antibodies found on repeat ABO typing. This report shares our experience on unexpected anti-B antibody findings in a patient with an A1B blood type. To the best of our knowledge, this is the first report of anti-B antibodies in a patient with an A1B blood type in Korea.