[Rare erythrocyte phenotypes imitating weak variant of antigen A]

Two phenotypes with defect of sialic acid in the cell membrane of erythrocytes due to some unknown factor, imitating the weak variant of antigen A are reported. One of them found in a healthy candidate for blood donation was called Tn. The second one associated with thrombocytopenia and anaemia differed from all as yet classified ones in that it had simultaneously increased expression of antigen H and lack of reaction with Dolichos biflorus lectin. For demonstrating the diagnostic difficulties differentiation against the weak variant of antigen A approaching A3 is described.