A Case of Cis-AB without B Antigen Expression / 대한수혈학회지

ABSTRACT

The cis-AB bood type is a rare phenomenon in which both the A and B blood types are inherited from a single parent. The cis-AB persons are not homogeneous with respect to reactivity of their red cells to anti-A and anti-B reagents, and are split into three groups with on the basis of the strength and characteristics of the serologic reactions; these reactivities are A2B3, A1B3 and A2B. A 7-year-old Korean boy was evaluated for paternity because he was presumptively identified as blood group AweakB and known blood types of his father and mother were A. In the repeated ABO blood typing, the child was typed as group A2B3 with weak anti-B, cis-AB being suspected. Both of his mother and father were typed as group A1 in cell and serum typing. In the saliva test and adsorption and elution studies of the parents, B substance was not detected. According to ABO genotyping, the child, mother and father showed cis-AB/O, A1/O and cis-AB/A1, respectively. The paternity was confirmed, but the father had unusual expression of cis-AB genotype. This was the second case of A1/cis-AB with phenotype A1, not expressing B antigen.