Alloimmunization to the D antigen by a patient with weak D type 21

Antibodies of apparent D specificity may be found in D+ patients. We report a D+, multi-transfused Caucasian woman with myelodysplasia who exhibited several alloantibodies. One antibody was a moderately strong (2+) anti-D that persisted for 9 months, until the woman died. Molecular analysis of the patient's RHD gene identified the rare weak D type 21 (938C > T) allele. D alloantibodies do not occur in patients with most weak D types, but some patients with a weak D phenotype, including those with type 21, can produce antibodies to nonself epitopes of the wild-type D antigen.