A novel B(weak) hybrid allele lacks three enhancer repeats but generates normal ABO transcript levels.
Background and Objectives Weak expression of A/B histo-blood group antigens is often explained by single nucleotide substitutions at the ABO locus. However, hybrid alleles containing segments from different ABO alleles can result in unexpected phenotypes and may complicate genotype analysis. We investigated the basis of weak B phenotype in a referred sample. Materials and Methods A healthy young w