Objective: To explore the genetic basis for an individual with a para-Bombay phenotype.
Methods: A proband with mismatched forward and reverse serotypes for the ABO blood group was identified. Weakly expressed ABH blood type antigen on the surface of red blood cells was verified by absorption and release test, and the blood group substances in saliva was detected by sialic acid test. Exons 6 and 7 of the ABO gene and exons of the FUT1 and FUT2 genes were subjected to direct sequencing.
Results: The proband was found to be of O type by forward ABO serotyping and AB type by reverse ABO serotyping, though H and substance A and B were detected in her saliva. DNA sequencing revealed that she has harbored c.35C/T, c.328G/A, and c.504delC compound heterozygous variants of the FUT1 gene. Haploid analysis showed that her FUT1 genotype was h328A/h35T+504delC, which has been uploaded to the NCBI website (No. MW323551).
Conclusion: The para-Bombay phenotype of the proband may be attributed to the novel compound heterozygous variants including c.504delC of the FUT1 gene, which may affect its function by altering the activity of FUT1 glycotransferase.