Fluorouracil (5-FU) induced acute immune haemolytic anaemia.

A female patient on Fluorouracil (5-FU) therapy for rectal carcinoma developed acute intravascular haemolysis with her fifteenth drug injection; a similar episode occurred later after a controlled challenge with the drug. A 5-FU-dependent complement-activating IgM antibody, which reacted with RBC in an indirect antiglobulin test, was detected in her serum. The antibody did not react with cord RBC, but a blood group specificity could not be determined. An excess of 5-FU in the indirect antiglobulin tests resulted in inhibition of these reactions.