Korean J Blood Transfus.  2020 Dec;31(3):254-259. 10.17945/kjbt.2020.31.3.254.

Rare ABO Allele Encoding Glycosyltransferase with Dual Specificity Found in a Cambodian Individual with the A 2 B Phenotype

  • 1Department of Health Sciences and Technology, SAIHST, Sungkyunkwan University, Seoul, Korea
  • 2Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea


Cis-AB and B(A) alleles encode an ABO enzyme with dual A and B glycosyltransferase activity. Although globally rare, the cis-AB phenotype is found relatively often in Korean, Japanese, and Chinese populations. Cases of the B(A) allele have been reported mostly in the Chinese population. Forward typing performed in a Cambodian woman with an ABO discrepancy demonstrated a strong reaction with anti-A and anti-B reagents, while there was no reaction with lectin anti-A 1. The anti-A 1 antibody was detected in reverse typing. Through ABO gene sequence analyses of exons 6 and 7, one of the alleles was identified as ABO*B.01. In contrast, the other allele harboring a c.803G>C substitution was either ABO*cisAB.05 or ABO*BA.06 allele. The ABO*cisAB.05 and ABO*BA.06 alleles remain indistinguishable despite routine serological testing and ABO genotyping. To the best of the author’s knowledge, this is the first case report of these variants discovered in a Cambodian individual residing in Korea.


ABO; Genotyping; Cis-AB; B(A)
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