Autoimmune hemolytic anemia and a further example of autoanti-Kpb

A 65-year-old Caucasian man with myelodysplasia was admitted with autoimmune hemolytic anemia and a Hb of 5.6 g/dL. The patient's serum contained anti-K; the DAT on the patient's RBCs reacted 3+ with anti-IgG and 3+ with anti-C3d. K- RBC units were transfused, but there was no sustained increase in Hb level. The samples were referred to the reference laboratory of the National Blood Service. The DAT results remained the same, with anti-K detected only in the serum. An eluate prepared from the patient's DAT-positive RBCs revealed anti-Kp(b) specificity. This study reports an unusual case of autoanti-Kp(b), which is different from previously published cases in that no free anti-Kp(b) was detectable in the serum.