Steroid Responsive T-Cell Mediated Pure Red Cell Aplasia Following Allogeneic Hematopoietic Stem Cell Transplantation

Pure red cell aplasia (PRCA) is an unusual complication following allogeneic hematopoietic stem cell transplantation (HSCT), the true incidence of which is not known. Almost all cases reported in the literature describe major ABO-incompatibility between the recipient and the donor as the major risk factor for this complication. Delayed recovery of reticulocyte counts and hypoplasia of erythroblasts in the marrow is attributed to incompatible hemagglutinins in recipients. There are reports of successful treatment of PRCA using different strategies include rapid tapering of calcineurin inhibitors, corticosteroids, donor lymphocyte infusion, rituximab, and/or plasma exchange. Additional causes of PRCA following allogeneic HSCT include parvovirus B19 infection and graft-versus-host disease (GVHD). The pathogenesis of PRCA in parvovirus infection is thought to be viral-mediated suppression of erythroid precursors in the bone marrow and this is due to the tropism of this virus for erythroid progenitor cells. Nonmyeloablative and reduced intensity conditioning regimens have been reported to have an increased risk of PRCA due to persistence of recipient lymphocytes. Here we report two cases of PRCA following allogeneic HSCT from major ABO mismatched donors. Both cases were correlated with the presence of a T-cell clone in the peripheral blood and bone marrow, and there was complete resolution of anemia with a short course of steroid treatment, as well as disappearance of the T-cell clone. Patient # 1 – A 24 year old female of Mediterranean descent underwent an HLA- 8/10 matched and major ABO-mismatched sibling donor bone marrow transplant for Sickle-Beta Thalassemia. She received a myeloablative but reduced toxicity conditioning regimen consisting of busulfan 16mg/kg, fludarabine 140mg/m², cyclophosphamide 105mg/kg, and alemtuzumab 52mg/m². Her immediate post-transplant course was relatively benign and significant for a mild CMV colitis which responded with resolution after treatment with anti-viral therapy. Her red cell transfusion needs had significantly decreased to every four weeks by day 130. However, at day 146 from HSCT, she started requiring red cell transfusions every two weeks, with a drop in the reticulocyte count to 0.6%. No antibodies were detected, and the patient was negative for parvovirus B19 and did not have any evidence of GVHD. However, her bone marrow showed an marked erythroid hypoplasia, and was positive for a T-cell clone with gamma chain gene rearrangement in the T-cell receptor. Due to a new onset of transfusion need, she was treated with a short course of steroids with an excellent response and disappearance of the T-cell clone from peripheral blood. She remained on immunosuppression during this entire period with a calcineurin inhibitor. Patient# 2 – A 10 year old Hispanic girl underwent a 10/10 HLA-matched and major ABO-mismatced sibling donor bone marrow transplant for idiopathic acquired severe aplastic anemia. Her preparative regimen consisted of 200 mg/kg of cyclophosphamide and 16mg/kg of rabbit-anti-thymocyte globulin. Her immediate post-transplant course was complicated by E.coli bacteremia. She had prompt engraftment and became transfusion independent on day 86. A cyclosporine taper was initiated at day 100 but held at day 119 when anemia was first noted. Peripheral blood showed a T-cell clone with gamma and beta chain gene rearrangement. She was started on a moderate dose of steroids with a good response, and has been tapered down to physiologic replacement dose of steroids with normal Hb and transfusion independence. With the resolution of anemia, the gamma chain gene rearrangement is not seen in the T-cell clonality assay, however, the beta chain gene rearrangement persists. To our knowledge, this is the first report of a T-cell mediated PRCA following allogeneic HSCT. Moreover, the PRCA was steroid responsive and not associated with GVHD in both the patients.