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Case Reports
. 2020 Dec;30(6):508-512.
doi: 10.1111/tme.12730. Epub 2020 Oct 26.

A novel ABO allele with a 21-bp duplication identified in two unrelated European individuals with weak A expression

Marianne A Jakobsen  1 , Annika K Hult  2 , Åsa Hellberg  2 , Sofia Lejon Crottet  3 , Ulrik Sprogøe  1 , Martin L Olsson  2   4
Affiliations
Case Reports

A novel ABO allele with a 21-bp duplication identified in two unrelated European individuals with weak A expression

Marianne A Jakobsen et al. Transfus Med. 2020 Dec.

Abstract

Objectives: To carry out genetic and serological analyses of a Swiss blood donor and a Danish patient carrying an aberrant ABO phenotype with weak A expression.

Background: ABO is the most clinically important blood group system but also one of the most complex. The system antigens are determined by carbohydrate structures generated by A and B glycosyltransferases encoded by the ABO gene. Genetic variants of ABO may encode a glycosyltransferase with reduced activity, leading to weak expression of A antigen.

Methods: Samples from two individuals were examined using genetic testing and extended immunohaematological evaluation, including standard serological methods, flow cytometry and analysis of plasma glycosyltransferase activity.

Results: Both individuals were serologically determined to be Aweak B. Genetic testing revealed that both were heterozygous for a novel ABO*A1.01-like allele with an in-frame duplication of 21 nucleotides in exon 7 (c.543_563dup), leading to the insertion of seven amino acids (QDVSMRR). Flow cytometric testing of native red blood cells (RBCs) showed very weak A antigen expression. This was in accordance with the enzyme activity test.

Conclusion: In summary, we describe a novel A allele with a duplication of 21 nucleotides in exon 7 that significantly decreases the enzyme activity and leads to very weak expression of A antigen. (200 words).

Keywords: ABO; blood group variant; weak A allele.

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References

REFERENCES

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