A delayed transfusion reaction caused by anti-K6.

This case report documents the demonstration of anti-K6 as the single antibody responsible for a delayed transfusion reaction. A 42-year-old white woman received three units of red blood cells for an episode of gastrointestinal bleeding from a duodenal ulcer. Twenty-three days following transfusion, laboratory and clinical evidence of hemolysis was noted. An anti-K6 was identified in the serum and in an eluate prepared from the patient's red blood cells. One of the three units transfused was positive for the K:6 antigen.