Conditioning with high-dose cyclophosphamide may not be sufficient to provide a long-term remission of paroxysmal nocturnal hemoglobinuria following syngeneic peripheral blood stem cell transplantation

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Abstract

A patient with paroxysmal nocturnal hemoglobinuria (PNH) received a syngeneic peripheral blood stem cell transplant (PBSCT) with high-dose cyclophosphamide (CY) conditioning. He had a reasonable engraftment and complete hematologic recovery. However, at 12 months after PBSCT, he became symptomatic and peripheral blood cells were almost entirely composed of glycosylphosphatidylinositol-anchored proteins deficient cells. This case suggests that high-dose CY may not exert a significant effect on PNH clones in the long term, although it had been effective in allogeneic BMT. In view of the possible autoimmune basis, it seems to be necessary to include other immunosuppressive therapy including ALG in addition to CY. Bone Marrow Transplantation (2001) 28, 987–988.

Main

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal disorder of hematopoietic stem cells characterized by recurrent intravascular hemolysis, pancytopenia, and a predisposition to venous thrombosis. PNH results from a somatic mutation of the PIG-A gene, that is responsible for glycosylphosphatidylinositol (GPI) anchor deficiency. Although the natural course of PNH is highly variable, patients with PNH finally die due to deep venous thrombosis, bone marrow failure-related complications, myelodysplastic syndrome, and leukemic progression. Among variable managements of PNH patients, bone marrow transplantation (BMT) has been considered to be the only potential curative treatment. In very rare circumstances in which the patient has a syngeneic donor, syngeneic BMT will be preferable to allogeneic BMT, because of the absence of GVHD. Among five reported cases of syngeneic BMT without a conditioning regimen, only one case achieved long-term survival1 and four cases showed a return to pathologic hematopoiesis.2,3,4,5 These data suggest that simple BM infusion without conditioning in PNH may not be an effective therapeutic option as noted in aplastic anemia. In this case, therefore, we have performed syngeneic transplantation by using the same conditioning regimen that has been used in allogeneic BMT.1

Case report

We have performed syngeneic transplantation in a 31-year-old man with high-dose cyclophosphamide conditioning and G-CSF-mobilized peripheral blood stem cells (PBSCs). He had received a syngeneic bone marrow infusion without conditioning 10 years ago. Two years later, he started to have frequent episodes of hemolysis and was maintained with steroids, iron replacement and transfusion. At the time of peripheral blood stem cell transplantation (PBSCT), Hb was 9.5 g/dl, WBC count 3.4 × 109/l and platelet count 79 × 109/l. Bone marrow aspiration revealed about 30–40% cellularity in the tissue section particles. Chromosome analysis showed no abnormality. For the stem cell source and conditioning regimen we used G-CSF-mobilized PBSCs harvested from the same syngeneic donor following cyclophosphamide at a dose of 50 mg/kg i.v. on each of 4 consecutive days. Harvested PBSCs were 25.38 × 108 MNCs/kg and 8.05 × 106 CD34+ cells/kg of the recipient. He was treated in a HEPA-filtered room and received antimicrobial prophylaxis and G-CSF (subcutaneous injection, 5 μg/kg) until neutrophils reached values above 0.5 × 109/μl. His WBC count reached 0.8 × 109/μl on day 9 and 2.2 × 109/μl on day 10 after PBSCT. His platelet count was increased to 53 × 109/μl without transfusion on day 16. He was discharged without any complications on day 19. Flow cytometric analysis of GPI-AP (CD66b (polymorphonuclear neutrophils, PMNs), CD59 (red blood cells, RBCs)) in the peripheral blood was performed by a direct immunofluorescent method before and after the PBSCT. The peripheral blood of the syngeneic donor was also analyzed as a control. Most of the patient's PMNs (98%) and RBCs (85%) were GPI-AP deficient cell population before PBSCT, but the GPI-AP expressed by normal cell populations were successively increased after PBSCT. At 9 months after PBSCT, the majority of the patient's PMNs (92%) and RBCs (90%) expressed GPI-AP. However 12 months after PBSCT, he again became symptomatic and his peripheral blood PMNs (98%) and RBCs (82%) were almost entirely composed of GPI-AP deficient cells. He remains alive with frequent hemolytic episodes and transfusion support (Table 1).

Table 1 Flow cytometric analysis of GPI-anchored protein (GPI-AP) on the peripheral blood PMNs and RBCs from the PNH patient before and after syngeneic PBSCT with high-dose cyclophosphamide

Discussion

We used high-dose CY as a conditioning regimen because it has been reported to be an effective immunosuppressive agent that could be beneficial to patients with severe aplastic anemia and PNH with aplastic anemia in BMT and has never shown secondary clonal disorder.6,7 The patient had reasonable engraftment and complete hematologic recovery but rapidly relapsed between 9 months and 12 months after syngeneic PBSCT. When we considered that clinically, development of PNH needs an abnormal PNH clone resulting from somatic mutation in PIG-A and an environment injurious to other hematopoietic stem cells through GPI-mediated mechanism, we could draw some inferences from this relapsed PNH case.8 First, CY alone may be not sufficient to eradicate the PNH clone and also in view of the possible autoimmune basis of aplastic anemia and of bone marrow aplasia with PNH, could not provide sufficient immune suppression. In the setting of a mixed chimeric state, it might be possible to imagine a scenario where the original disease process could attack the normal donor marrow and the minimized PNH clone could expand again. Unfortunately, we could not determine the characteristics of relapsed PNH clone because we did not evaluate the underlying PIG-A mutation.5,9 Second, allogeneic transplantation following non-myeloablative conditioning regimens has cured PNH regularly1,6,10 whereas relapse is common after syngeneic transplantation.2,3,4,5 This suggest that an allo-reactive mechanism might contribute to the success of BMT for PNH, either by helping to eradicate autoreactive T cells, or the PNH clone, or both.

Syngeneic transplantation in PNH could also provide useful insights into the pathophysiology of the disease as it has in aplastic anemia. We thought that in this case, PNH relapse might result from persistence of the autoimmune process, with emergence of a new PNH clone or re-growth of the original PNH clone. This case might support the hypothesis that an autoimmune process might be closely related to pathological environment for the clonal selection of PNH clone through a GPI-mediated mechanism.5,8 We suggest that it might be helpful to include other immunosuppressive agents such as anti-lymphocyte globulin (ALG) in transplant conditioning in patients with PNH in addition to CY.

References

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Cho, S., Lim, J., Kim, Y. et al. Conditioning with high-dose cyclophosphamide may not be sufficient to provide a long-term remission of paroxysmal nocturnal hemoglobinuria following syngeneic peripheral blood stem cell transplantation. Bone Marrow Transplant 28, 987–988 (2001) doi:10.1038/sj.bmt.1703259

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Keywords

  • paroxysmal nocturnal hemoglobinuria
  • high-dose cyclophosphamide
  • syngeneic peripheral blood stem cell transplantation

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