J Clin Pathol Qual Control.  2001 Dec;23(2):325-329.

A Case of Cis-AB Child from a Group O Father and a Group A Mother

• Song EY
• Jeon DS
• Seo DH
• Han KS

Abstract

Cis-AB is a rare variant of the ABO blood group, which is characterized by the inheritance of both A and B genes on one chromosome. The cis-AB blood group has been classified into three different phenotypes (A1B3, A2B3, A2B) according to coexisting another ABO genes. In individuals with cis-AB/A1 genotype, the red blood cells react strongly with reagent anti-A and reagent anti-A1 as A1 phenotype, and react weakly with reagent anti-B. Usually the serum react weakly with reagent B cells. We report a case of cis-AB/A1 genotype, which does not express B antigen and shows relatively strong reactivity with reagent B red cells. A 7-year-old girl visited Keimyung University Hospital for paternity because she had been typed as blood group AB at her school although known blood types of her father and mother were O and A, respectively. On ABO blood grouping, her blood group was identified as AweakB with weak anti-B, therefore cis-AB blood group (A2B3) was suspected. However, her father and mother were typed as O and A1 blood group, respectively and we could not explain the inheritance pattern. HLA typing of the family was done and the paternity could be confirmed. To explain this discrepancy, ABO genotyping was performed and the genotypes of the girl, father and mother were determined as cis-AB/O, O/O and cis-AB/A1, respectively. This is the second reported case of cis-AB/A1, without the expression of B antigen in Korea. ABO genotyping was the only tool to clarify the inheritance pattern of ABO genes in this case.

MeSH Terms

B-Lymphocytes
Blood Grouping and Crossmatching
Child*
Erythrocytes
Fathers*
Female
Genotype
Histocompatibility Testing
Humans
Inheritance Patterns
Korea
Mothers*
Paternity
Phenotype
Wills