RESUMO
OBJECTIVE@#To investigate the serological and molecular characteristics of a pedigree carrying an allele for ABO*BW.11 blood subgroup.@*METHODS@#The ABO blood type of 9 pedigree members were determined by serological methods. Exons 6 and 7 of the ABO gene were amplified by PCR and directly sequenced. The patient and her father were also subjected to clone sequencing analysis.@*RESULTS@#Serological tests demonstrated that the proband and her younger brother had an ABw subtype, whilst her father and two daughters had Bw subtype. Clone sequencing found that the exon 7 of the ABO gene of the proband had a T>C substitution at position 695, which was identified as a BW.11 allele compared with the reference sequence B.01. This BW.11 allele was also identified in the proband's father, brother and two daughters. Due to allelic competition, the A/BW.11 and BW.11/O alleles demonstrated significantly different phenotypes.@*CONCLUSION@#The c.695T>C substitution of the ABO gene may lead to allelic competition in the Bw11 subtype. Combined molecular and serological methods is helpful for precise blood grouping.