B para-Bombay phenotype in China caused by homozygous mutation for site 328 G > A of FUT1 gene: a case report

The aim of this paper is to accurately identify a case of B para-Bombay and to analyze the genetic mutation. ABO and Lewis blood groups were identified by standard serological methods, and trace antigens on RBCs were detected by adsorption-elution test, while blood group substances in the saliva were detected by agglutination inhibition test. The ABO gene exons 6-7, FUT1 gene exon 4 and FUT2 gene exon 2 were directly sequenced. Serological results showed that there were B antigens on RBCs without H antigens, anti-A and anti-HI antibodies in serum, and B and H blood group substances in the saliva. The Lewis phenotype was Le (a-b+). According to gene sequencing analysis, ABO, FUT1 and FUT2 genotypes were B101/O02, h^328G/Ah3^28G/A and Se^357C/TSe^357C/T, respectively. This rare phenotype can be mislabeled as "O" if any of the detailed investigations are not performed. Therefore, in order to ensure the safety of blood transfusion, genetic and serological tests are necessary for the correct identification of difficult blood groups.