Pure red cell aplasia after allogeneic stem cell transplantation with reduced conditioning.

Conditioning regimens with reduced intensity are used increasingly for allogeneic stem cell transplantation in elderly or extensively pretreated patients. Two cases of pure red cell aplasia after fludarabine-based conditioning and during immunosuppression with cyclosporin are described. Both patients received ABO-mismatched stem cells and had anti-donor isoagglutinins. Red cell recovery occurred after extended immunosuppression when isoagglutinins had disappeared. Colony assays indicated serologic suppression of the erythrocyte lineage in one patient. Since reduced conditioning permits donor cell engraftment primarily by suppression of host T cells, antibody-mediated immunological complications may occur more frequently than after 'classical' conditioning.