Alloanti-c/ce in a c+ceAR/Ce patient suggests that the rare RHCE ceAR allele (ceAR) encodes a partial c antigen.

BACKGROUND: ceAR (RHCE ceAR) is a rare RH allele encountered in people of African/Caribbean ancestry, known to encode a partial e antigen. The homozygous ceAR/ceAR genotype encodes the rare blood group Hr-. This study describes alloanti-c/ce in a ceAR/Ce patient, suggesting that ceAR also encodes a partial c antigen.

CASE REPORT: A 21-year-old patient suffering from intermediate beta-thalassemia, with transfusion history, was hospitalized for severe anemia. Blood samples were referred to the National Reference Laboratory for suspicion of a mixture of alloantibodies or an alloantibody to a high-prevalence antigen.

MATERIALS AND METHODS: Standard hemagglutination methods were performed to investigate the patient's RBCs and serum. A molecular analysis of RHD and RHCE was carried out by allele-specific polymerase chain reaction and DNA sequencing.

RESULTS: Blood type performed by the referring laboratory was B, D+C+E-c+e+, K-. Several antibodies were identified: anti-c/ce, anti-Fy(b), anti-Jk(a), and anti-S. Full serologic investigations showed that anti-c/ce could be very likely considered as an alloantibody. The patient's genotype was ceAR/Ce. Anti-c/ce reacted with ceAR/ceEK, ceEK/ceEK, and ceAR/ceBI but not with ceAR/ceAR, ceMO/ceMO, and ce(s)(340)/ce(s)(340) RBCs.

CONCLUSION: This is the first case of alloanti-c/ce related to ceAR, suggesting that this rare RHCE allele encodes a partial c antigen. The presence of the C antigen in the patient allowed for the partial expression of the c antigen encoded by ceAR. The c antigen encoded by ceAR appeared to be different than that encoded by ceEK and ceBI and may share common lacking epitopes with the c antigens encoded by ceMO and ce(s)(340).