[AB-cis phenotype with expression similar to AB-el].

We studied a discrepancy between red blood cells and serum test. The red cell test was identified as an A group, and the serum test as an AB group. Then we performed adsorption-elution and saliva test, in order to demonstrate A, B and H substances. We found that the blood group was AB, and the B antigen belonged to a weak group named Bel. We studied her parent blood groups. Her mother was AB and her father 0. We conclude that the blood group belonged to an cis-AB phenotype and the B antigen was a weak Bel variant.