Difficulties in Managing a Sickle Cell Patient with a Variant C Antigen and Multiple Alloantibodies Including Anti-Dombrock a

We present a unique case of sickle cell disease with variant C antigen and multiple alloantibodies including Anti-Dombrock a (Do_a) that presented as a challenge in transfusion management.

A 20-year-old female sickle cell patient is on multiple and frequent transfusions (~25/year). She has a history of anti-Fy_a, anti-C, anti-K, anti-S, anti-M, anti-Le_a, and warm autoantibodies. Recently, she presented with anti-C alloantibody even though she was C antigen positive by antisera testing, so genotyping was done. The 3 nucleotide substitutions detected in the RhD gene (186G>T, 410C.T, 455A>C) and the RhCE gene (48G>C, 733C>G, 1006G>T) constituted a genotype of Dce/C_vare_par and a predicted phenotype of D+altered C+E-c+e+VS+V-hr_B+.

She has also developed indirect antiglobulin testing reactivity that 'comes and goes' despite being given phenotype matched blood. The reactivity that comes and goes was identified as Anti-Do_a using the Do_a negative genotype and an extended antibody ID panel.

Some variant C antigens act as partial C antigen, thus, these patients may make anti-C alloantibody. The frequency of Do_a antigen is 66.7~55% depending on race, but reagent antisera for Do_a antigen is not commercially available yet. Anti-Do_a can disappear in vivo but can cause delayed and acute/hemolytic transfusion reactions. We have been giving her genotype matched blood. Such a patient with multiple RBC antibodies on chronic transfusions presents as a challenge in transfusion management that mandates extensive testing. The extensiveness of the pretransfusion testing in these patients is left to the individual pathologist's decision.

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