Warm autoimmune hemolytic anemia with anti-Jk a specificity following babesiosis masquerading as a delayed hemolytic transfusion reaction.

Healthcare providers should be cognizant of the potential for babesiosis-induced WAIHA, particularly in individuals who continue to hemolyze despite undetectable parasitemia. Furthermore, this case highlights the possibility for warm autoantibodies to demonstrate Kidd antigen specificity. Though Kidd antigen variants are rare, antigen genotyping may be beneficial, particularly in the context of recent RBC transfusions, which typically preclude accurate serological phenotypic assessment.