Severe haemolytic disease of a newborn with variant D mimicking blocked-D phenomenon.

Anti-D is still the most common antibody causing severe haemolytic disease of the fetus and newborn (HDFN). In a mother with a very high titer of anti-D, antibodies can coat and block the D antigens on the red blood cells of the newborn. This blocking phenomenon prevents agglutination of the D-positive red cells with the IgM anti-D typing reagent, giving false negative results. Here, we report the case of a newborn with variant D phenotype and severe HDFN, which mimicked the blocked-D phenomenon, which, at the first instance, confused both the treating clinicians and the transfusion service personnel.