Abstract
Introduction: Ael is known to be one of the weakest A subgroups and can be identified through either the adsorption-elution technique or molecular analysis. Single nucleotide variation in the ABO gene can potentially disrupt the function of ABO glycosyltransferase, resulting in decreased ABO antigen expression. Case presentation: We reported 1 case of the missense SNV c.1024A>C in the ABO*A1.02 allele was associated with an Ael phenotype. The proband was a 19-year-old male Chinese Han blood donor who was initially stereotyped as type B. Based on the findings from absorption elution, genotype tests, and a family investigation, both the proband and his mother were classified as the AelB phenotype. An uncommon allele was detected in both the proband and his mother, differing by a single nucleotide at position 1,024 from A to C (c.1024A>C) when compared to the ABO*A1.02 allele. The c.1024A>C SNV induces an amino acid substitution, specifically p.Thr342Pro, which consequently leads to the loss of two sheets (p214-p216, p340-p344) in the wild-type A glycosyltransferase (GTA) 3D structure. The removal of these two sheets, situated at the protein's core, implies the occurrence of an interaction within this domain that affects the stability of the protein structure. Conclusion: AelB is prone to misidentification as type B, and the accurate determination of blood type can be achieved through the integration of the adsorption-elution technique and molecular analysis.