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

BACKGROUND

RHCEceEK 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 RHD01N.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 was detected in her plasma. She was found to carry a normal RHD gene, a conventional RHCEceEK allele and an alternative RHCEceEK allele (RHCEceEK without c.48G>C). The family study showed that the conventional RHCEceEK and the alternative RHCEceEK alleles were associated with a RHD01 allele and a RHD01N.01 allele, respectively. Molecular analysis performed in the proband's mother showed a novel RHCEce variant allele on a RHCEce -like background (RHCEce with c.609G>A).

CONCLUSIONS

This case study brought out new associations between RHD and RHCE alleles encoding the rare Hr- phenotype: the conventional RHCEceEK allele linked to the RHD01 allele and an alternative RHCEceEK allele associated with the RHD01N.01 allele. A novel RHCEce variant (RHCEce with c.609G>A) was also reported.