A male patient in first remission of acute myeloid leukemia was offered a hemopoietic cell transplant from an unrelated female donor. He received reduced-intensity conditioning (RIC) with Fludarabine 30 mg/m2 iv × 5 day, Busulphan 3.2 mg/kg iv × 2 days, and Alemtuzumab 20 mg/day iv × 5 days, followed by donor blood stem cell infusion. The cell dose was 3.7  ×  106 CD34+ cells per kilogram recipient weight. Cyclosporine A was administered from day +1.

On day 7, the patient developed fever (38.4°C) and dry cough; he was given Gentamycin, Piperacillin, and granulocyte colony-stimulating factor. Three days later amikacin and vancomycin were introduced as the second antibiotic line. Bacterial cultures were negative. Chest X-ray showed no lung consolidation. CT of the chest showed diffuse small opacities in the lower and middle parts of both lungs. Voriconazole and high-dose Sulphametoxazole/Trimethoprim were added to treatment. Over the next days the fever subsided.

On day +21, his hematological findings were: white cell count of 1.2  ×  109/l, with 45% neutrophils; platelet count 22  ×  109/l (without transfusion); hemoglobin of 8.3 g/dl. He received two units of red cells. On day +28, WCC was 3.4  ×  109/l with 62% neutrophils; platelet count was 57  ×  109/l; hemoglobin was 7.5 g/dl.

Patient’s original blood group was A, RhD negative; the donor was AB, RhD positive. The patient was transfused with group A, RhD negative red cells. Prior to transplantation, the patient’s anti-B titer was 128. On day +56, his red cells tested positive with anti-A, negative with anti-B and anti-D; anti-B was detected in the plasma with the titer 16. Direct antiglobulin test was negative.

On day +60, the patient’s hemoglobin was 8.1 g/dl; reticulocytes 7  ×  109/l; platelets 144  ×  109/l; Neutrophils 4.7  ×  109/l; Bilirubin 20 μmol/l; LDH 190 iu/l; and Ferritin 880 ng/ml. DNA analysis of peripheral blood cells chimerism showed 84% CD3+ cells and 100% CD15+ cells of donor origin. The patient was transfused red cells to maintain the hemoglobin above 8.0 g/dl, requiring an average of 1.5 red cell units per week for the following 4 months.

Fig. 6.1
figure 1

Pure red cell aplasia. Bone marrow aspirate showing granulocytic cells, a plasma cell, a few lymphocytes, and a single basophilic erythroblast (arrow) (Courtesy of Professor Judith Marsh, King’s College Hospital)

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Fig. 6.2
figure 2

Pure red cell aplasia. Bone marrow trephine showing several megakaryocytes, numerous granulocytic cells in various stages of maturation, and a paucity of erythroblasts (Courtesy of Professor Judith Marsh, King’s College Hospital)

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Fig. 6.3
figure 3

Blood product selection after ABO-mismatched transplant. Red squares: major ABO mismatch; yellow squares: minor mismatch; blue squares: bidirectional mismatch. Policies are applied until recipient’s anti-A/B is undetectable and DAT negative (for major and bidirectional mismatch), or until complete conversion to donor ABO group and a negative DAT (in minor mismatch)

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Q1. What is your diagnosis and how would you confirm it?

A1. The scenario is suggestive of post-transplant pure red cell aplasia (PRCA) due to a major ABO incompatibility between the recipient and the donor. The incidence of PRCA in this setting is reported to be 10–30%. While platelet and neutrophil regeneration proceeds without impediment, erythroid regeneration is delayed, as evidenced by continuing transfusion dependence and low reticulocyte counts beyond day +60 after transplantation. Bone marrow aspirate or trephine biopsy shows a paucity of erythroid cells, often “arrested” at early erythroblast stage, with normal maturation of other lineages (Figs. 6.1 and 6.2).

Q2. How would you manage post-transplant PRCA ?

A2. There is no established treatment for post-transplant PRCA. Erythroid regeneration often occurs spontaneously, as host hemagglutinin titers decline, although this may take several months. Favorable responses have been reported with steroids, plasma exchange, antithymocyte globulin, and erythropoietin. Immune modulating maneuvers, such as cyclosporine withdrawal or infusions of donor lymphocytes, have been successful in some cases; however, their benefit must be weighed against the risk of GVHD exacerbation.

Cyclosporine A dose was tapered from day +90. By day +120, reticulocyte count was 25  ×  109/l, reaching stable normal levels (>50  ×  109/l) 140 days after transplant. Day +90 anti-B titer was 4, becoming undetectable after day +120.

Q3. What blood group should be the red cells, platelets, and plasma transfused in the setting of ABO-mismatched hemopoietic cell transplantation?

A3. In major ABO mismatch, recipient type red cells should be used until host hemagglutinin(s) has(ve) become undetectable, and the DAT becomes negative. Donor type red cells can be given from this point. In practice, this means that group O red cells should be used, with the exception of a group A (or B) recipient, receiving hemopoietic cells from an AB donor; in this case, group A (or B) red cells can be used (see the case above). Platelets and plasma should be of donor type. In general, group O platelets are the least preferred choice, to avoid transfusion of products with high-titer hemagglutinins. In minor ABO mismatch, red cells should be of donor type (again most commonly group O!), while platelets and plasma should be recipient type. About 5–7% of allogeneic transplants are bidirectional, i.e., recipient group A, donor group B, or vice versa. For these patients, group O red cells and AB plasma are recommended. First choice platelets are group AB; however, as these are not always available, second choice platelets are those of recipient type (Fig. 6.3).

Q4. What is the impact of a RhD mismatch in hemopoietic cell transplantation?

A4. Transplantation from a RhD positive donor into a RhD negative recipient seldom causes sensitization to RhD, as the recipient tends to be profoundly immunosuppressed around the time of transplant. Nevertheless, transfusion of RhD-negative red cells until conversion to donor type is recommended. In the reciprocal situation, donor-derived lymphocytes may produce anti-D, causing passenger lymphocyte hemolysis. Rh antibodies have not been reported to cause red cell aplasia.

COMMENTARY

Unlike its critical importance in solid organ transplantation, the impact of ABO mismatch on survival, relapse, and GVHD incidence after hemopoietic cell transplantation (HCT) is somewhat controversial. While some reports claimed increased incidence of GVHD in ABO minor-mismatched patients, others deny a significant effect. Similarly, ABO-mismatch was found to significantly reduce survival in some studies, but not in others. It should be borne in mind that survival, as well as GVHD incidence after HCT, depend on a multitude of factors, and has improved over the years as a result of more sophisticated HLA typing, newer conditioning regimens, and better supportive therapy. Clearly, the answer to these questions requires a systematic review of a large number of transplanted patients.

Notwithstanding its impact on major transplant outcomes, ABO mismatch is associated with distinct immunological complications after HCT. Minor ABO incompatibility may cause “passenger lymphocyte syndrome” (see “ COMMENTARY ” to Case 5). Major ABO incompatibility can lead to: (1) immediate hemolysis of donor red cells, especially if using bone marrow as source of HSC; in such cases, preventative removal of red cells from donor’s bone marrow should be performed; (2) delayed erythroid engraftment/PRCA; (3) rarely, hemolysis of newly produced donor red cells due to persisting host hemagglutinins, usually occurring around days 60–70 after transplant.

Bolan et al. (2001) argued that host hemagglutinin disappearance is delayed after RIC, compared to standard conditioning transplants, leading to higher incidence of PRCA. Conversely, a study of 134 HSC transplants (Mijovic et al. 2008) showed virtually identical host hemagglutinin kinetics between reduced-intensity and standard conditioning transplants. A notable difference between the two studies was that the latter used Alemtuzumab as part of conditioning, which may have had a profound effect on host immune response.

In addition to alloimmune post-transplant hemolytic reactions, autoimmune hemolytic anemia complicates 2–3% of allogeneic HSC transplants, although some reports quote higher rates in T-cell-depleted transplants. Unlike the “passenger lymphocyte” syndrome and ABO-related PRCA, which occur in the immediate aftermath of HSC transplantation, peak onset of AIHA is 7–10 months after transplantation, with the range of 2–24 months. Post-transplant AIHA is often resilient, but serologically indistinguishable from the idiopathic one.