A novel FY*A allele with the 265T and 298A SNPs formerly associated exclusively with the FY*B allele and weak Fyb antigen expression: implication for genotyping interpretative algorithms

Background and Objectives An Australian Caucasian blood donor consistently presented a serology profile for the Duffy blood group as Fy(a+b+) with Fya antigen expression weaker than other examples of Fy(a+b+) red cells. Molecular typing studies were performed to investigate the reason for the observed serology profile. Material and Methods Blood group genotyping was performed using a commercial SNP microarray platform. Sanger sequencing was performed using primer sets to amplify across exons 1 and 2 of the FY gene and using allele-specific primers. Results The propositus was genotyped as FY*A/B, FY*X heterozygote that predicted the Fy(a+b+w) phenotype. Sequencing identified the 265T and 298A variants on the FY*A allele. This link between FY*A allele and 265T was confirmed by allele-specific PCR. Conclusion The reduced Fya antigen reactivity is attributed to a FY*A allele-carrying 265T and 298A variants previously defined in combination only with the FY*B allele and associated with weak Fyb antigen expression. This novel allele should be considered in genotyping interpretative algorithms for generating a predicted phenotype.