A Tutsi family harbouring two new RHCE variant alleles and a new haplotype in the Rh blood group system

Abstract

Background: RHCE*ceEK is a rare RH allele mostly encountered in people of African descent. This allele is defined by four single nucleotide substitutions: c.48G>C, c.712A>G, c.787A>G and c.800T>A. Until now, it has only been reported to segregate with either RHD*01N.01 or RHD*DAR1.00.

Materials and methods: Blood samples were drawn from a 32-year-old Tutsi pregnant woman during an antenatal visit in order to perform her type and screen. To further investigate the results found in the patient, a family study was conducted. Standard haemagglutination methods were used to investigate the subjects' red blood cells and plasma. Molecular workup on RHD and RHCE genes was carried out by DNA microarray, real-time PCR and DNA sequencing techniques.

Results: The patient was phenotyped as group B, D+C-E-c+e+, Hr-. A complex mixture of anti-E, anti-c, anti-Hr and anti-hr^S was detected in her plasma. She was found to carry a normal RHD gene, a conventional RHCE*ceEK allele and an alternative RHCE*ceEK allele (RHCE*ceEK without c.48G>C). The family study showed that the conventional RHCE*ceEK and the alternative RHCE*ceEK alleles were associated with a RHD*01 allele and a RHD*01N.01 allele, respectively. Molecular analysis performed in the proband's mother showed a novel RHCE*ce variant allele on a RHCE*ce^S -like background (RHCE*ce^S with c.609G>A).

Conclusions: This case study brought out new associations between RHD and RHCE alleles encoding the rare Hr- phenotype: the conventional RHCE*ceEK allele linked to the RHD*01 allele and an alternative RHCE*ceEK allele associated with the RHD*01N.01 allele. A novel RHCE*ce variant (RHCE*ce^S with c.609G>A) was also reported.

Keywords: RHCE*ceEK; Hr−; RH:-18; anti-Hr; anti-RH18.