A novel FY *A allele with the 265T and 298A SNP s formerly associated exclusively with the FY *B allele and weak Fy b 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 Fy a 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 Fy a 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 Fy b antigen expression. This novel allele should be considered in genotyping interpretative algorithms for generating a predicted phenotype.