Rh antibodies as a result of altered Rh epitopes on transfused red cells: a case series of seven Brazilian patients.

Background: Rh antibodies produced by patients receiving Rh-matched RBC units may be associated with inheritance of altered RH alleles or a result of altered Rh epitopes on donor red blood cells (RBC). On this background, our aim was to evaluate unexpected Rh antibodies in Brazilian patients receiving regular transfusions and determine the clinical significance of the alloantibody produced.

Material And Methods: We investigated seven patients (5 with sickle cell disease, 1 with myelodysplastic syndrome and 1 with β-thalassaemia) with unexplained Rh antibodies. All patients had complete serological and molecular analyses. A lookback at the donor units transfused to these patients was performed and donors suspected of having Rh variants were recruited for further analysis. Laboratory and clinical findings were used to evaluate the clinical significance of the alloantibodies produced.

Results: The unexpected Rh antibodies found in the patients were not linked to the expression of partial Rh phenotypes according to serological and molecular analyses. Anti-D was found in two patients, anti-C was found in one patient, anti-c was found in one patient and anti-e was found in three patients carrying conventional D, C, c and e antigens respectively. Serological and molecular analyses of donors' samples revealed that six donors whose RBC were transfused to these patients carried partial Rh antigens. Only one anti-e in a patient with β-thalassaemia was autoreactive and could not be explained by RH diversity in his donors. Three of the seven Rh antibodies were associated with laboratory and clinical evidence of a delayed haemolytic transfusion reaction or decreased survival of transfused RBC at first detection.

Discussion: Our study provides evidence that patients exposed to RBC units from donors with Rh variants may develop antibodies and some of these may be of clinical significance.