[FLT3-ITD mutation-positive acute myeloid leukemia undergoing clonal transition with PTPN11 mutation at relapse].

A 28-year-old man was diagnosed with acute myelomonocytic leukemia. He achieved complete remission (CR) after two cycles of induction therapy. However, after consolidation therapy, bone marrow aspiration performed to prepare for allogeneic hematopoietic stem cell transplantation revealed disease relapse. Companion diagnostics confirmed the presence of the FLT3-ITD mutation. The patient received gilteritinib monotherapy and achieved CR. Subsequently, he underwent unrelated allogeneic bone marrow transplantation. One year after transplantation, the patient relapsed, and gilteritinib was resumed. However, the leukemia progressed, and panel sequencing using a next-generation sequencer showed that the FLT3-ITD mutation disappeared. A mutation in PTPN11, which regulates the RAS/MAPK signaling pathway, was also detected. Gilteritinib was discontinued, and the patient achieved CR with salvage chemotherapy. He underwent related haploidentical peripheral blood stem cell transplantation but died of relapse. This was a case in which genetic analysis revealed clonal transition and acquisition of resistance to treatment.

[Ruptured mycotic cerebral aneurysm in an adult T-cell leukemia/lymphoma patient undergoing allogeneic stem cell transplantation].

A 63-year-old man with adult T-cell leukemia-lymphoma underwent allogeneic bone marrow transplantation from an HLA-matched unrelated donor. On day 17 after transplantation, chest computed tomography (CT) showed nodules in the lower lobes of both lungs, and invasive pulmonary aspergillosis (IPA) was suspected. Treatment with liposomal amphotericin B was started, and improvement of infectious lesions was confirmed with CT on day 28. The antifungal agent was changed to voriconazole on day 52 because of progressive renal dysfunction. Disorders of consciousness and paralysis of the left upper and lower extremities developed on day 61. Brain CT showed subcortical hemorrhage in the right parietal and occipital lobes, and the patient died on day 62. An autopsy revealed filamentous fungi, suspected to be Aspergillus, in the pulmonary nodules and a ruptured cerebral aneurysm. Although IPA occurs in 10% of transplant recipients, vigilant monitoring for mycotic cerebral aneurysms is required to prevent hematogenous dissemination of Aspergillus, which is associated with a high mortality rate.

[Kidney transplantation for end-stage renal disease after third allogeneic hematopoietic stem cell transplantation for Philadelphia chromosome-positive acute lymphoblastic leukemia].

An 18-year-old man underwent allogenic bone marrow transplantation (BMT) for Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ALL). Ph+ALL relapsed 3 months after the first BMT, and the patient underwent a second BMT. However, Ph+ALL relapsed 4 months after the second BMT, and he received a haploidentical peripheral blood stem cell transplantation (haplo-PBSCT) from his father. Molecular complete remission was confirmed 29 days after haplo-PBSCT. However, the patient needed dialysis for end-stage renal disease due to thrombotic microangiopathy 3 years and 2 months after haplo-PBSCT. He received a kidney transplantation from his father 7 years and 10 months after haplo-PBSCT, and got off dialysis after the kidney transplantation. Immunosuppressive therapy with methylprednisolone, tacrolimus, and mycophenolate mofetil was started for kidney transplantation, but the dose of immunosuppressive agents was reduced successfully without rejection soon after kidney transplantation. The patient has maintained long-term remission since the haplo-PBSCT, and his kidney function was restored by the kidney transplantation from his father.

Risk factors for CAR-T cell manufacturing failure among DLBCL patients: A nationwide survey in Japan.

For successful chimeric antigen receptor T (CAR-T) cell therapy, CAR-T cells must be manufactured without failure caused by suboptimal expansion. In order to determine risk factors for CAR-T cell manufacturing failure, we performed a nationwide cohort study in Japan and analysed patients with diffuse large B-cell lymphoma (DLBCL) who underwent tisagenlecleucel production. We compared clinical factors between 30 cases that failed (7.4%) with those that succeeded (n = 378). Among the failures, the proportion of patients previously treated with bendamustine (43.3% vs. 14.8%; p < 0.001) was significantly higher, and their platelet counts (12.0 vs. 17.0 × 104 /µL; p = 0.01) and CD4/CD8 T-cell ratio (0.30 vs. 0.56; p < 0.01) in peripheral blood at apheresis were significantly lower than in the successful group. Multivariate analysis revealed that repeated bendamustine use with short washout periods prior to apheresis (odds ratio [OR], 5.52; p = 0.013 for ≥6 cycles with washout period of 3-24 months; OR, 57.09; p = 0.005 for ≥3 cycles with washout period of <3 months), low platelet counts (OR, 0.495 per 105 /µL; p = 0.022) or low CD4/CD8 ratios (

[Polatuzumab vedotin, bendamustine, and rituximab in patients with relapsed/refractory diffuse large B-cell lymphoma, including the outcome as a bridging treatment to CAR-T cell therapy or allogeneic hematopoietic stem cell transplant].

Pola-BR (polatuzumab vedotin, bendamustine, and rituximab) therapy received approval for relapsed/refractory diffuse large B-cell lymphoma (R/R DLBCL) in Japan in March 2021. There have been few reports on the efficacy and safety of Pola-BR therapy in Japanese clinical practice. A retrospective analysis was performed on twenty-nine patients with R/R DLBCL who received Pola-BR therapy at our institution (intent to cellular immunotherapy cohort: 20 patients, stand-alone treatment cohort: nine patients). The overall response rate was 69.0% (complete response 27.6%). The median progression-free survival was 5.1 months, with a 9.5-month median overall survival. In the intent to cellular immunotherapy cohort, 11 of 19 patients received chimeric antigen receptor T-cell (CAR-T) infusions, and one patient received allogeneic stem cell transplantation. Four patients received Pola-BR therapy, including bendamustine before leukapheresis, and all produced CAR-T products successfully. 3 of the 28 patients experienced grade3 or higher adverse events, and two required treatment discontinuation. Our single institution, a real-world cohort of R/R DLBCL patients showed high efficacy outcomes and a tolerable toxicity profile for Pola-BR therapy, which is comparable to previous studies. More cases are needed to determine its impact on CAR-T therapy and stem cell transplantation.

[Manufacturing results of tisagenlecleucel for acute lymphoblastic leukemia: a survey by the CAR-T cell therapy taskforce of the Japan Society of Transfusion Medicine and Cell Therapy].

The frequency of the manufacturing failure of chimeric antigen receptor (CAR)-T cell therapy in clinical practice is unknown. To clarify the current state of how likely CAR-T cell production is to succeed or fail for B-cell acute lymphoblastic leukemia (B-ALL), we analyzed cases in which the production of tisagenlecleucel was performed for patients with B-ALL at 15 facilities in Japan from October 2019 to March 2022. Total 81 patients (47 males and 34 females) were analyzed. The median age at apheresis was 13 years (1-25) with a median number of prior treatments of 4 (1-9). The numbers of patients with histories of allogeneic transplantation, inotuzumab ozogamicin, or blinatumomab treatments were 51 (63.0%), 26 (32.1%), and 37 (45.7%), respectively. The median blast percentage and CD3+ cell counts in peripheral blood were 0% (0-91.5), and 611/µl (35-4,210) at apheresis, and the median number of CD3+ cells shipped was 2.2×109 (0.5-8.3). While cases with a history of heavy prior treatment before apheresis were included, no manufacturing failures were observed. Continuing to monitor the status of manufacturing failures is necessary as the number of B-ALL cases treated with CAR-T cell therapy increases.

Comparison of cryoprotectants in hematopoietic cell infusion-related adverse events.

BACKGROUND: The standard cryoprotectant for human cellular products is dimethyl sulfoxide (DMSO), which is associated with hematopoietic cell infusion-related adverse events (HCI-AEs) in hematopoietic stem cell transplantation including peripheral blood stem cell (PBSC) transplantation (PBSCT). DMSO is often used with hydroxyethyl starch (HES), which reduces DMSO concentration while maintaining the postthaw cell recovery. The cryoprotectant medium CP-1 (Kyokuto Pharmaceutical Industrial) is widely used in Japan. After mixture of a product with CP-1, DMSO and HES concentrations are 5% and 6%, respectively. However, the safety profile of CP-1 in association with HCI-AEs has not been investigated. STUDY DESIGN AND METHODS: To compare CP-1 with other cryoprotectants, we conducted a subgroup analysis of PBSCT recipients in a prospective surveillance study for HCI-AEs. Moreover, we validated the toxicity of CP-1 in 90 rats following various dose administration. RESULTS: The PBSC products cryopreserved with CP-1 (CP-1 group) and those with other cryoprotectants, mainly 10% DMSO (non-CP-1 group), were infused into 418 and 58 recipients, respectively. The rate of ≥grade 2 HCI-AEs was higher in the CP-1 group, but that of overall or ≥grade 3 HCI-AEs was not significantly different, compared to the non-CP-1 group. Similarly, after propensity score matching, ≥grade 2 HCI-AEs were more frequent in the CP-1 group, but the ≥grade 3 HCI-AE rate did not differ significantly between the groups. No significant toxicity was detected regardless of the CP-1 dose in the 90 rats. CONCLUSIONS: Infusion of a CP-1-containing PBSC product is feasible with the respect of HCI-AEs.

[Tisagenlecleucel for relapsed/refractory diffuse large B-cell lymphoma: real-world data from single institute experience].

Chimeric antigen receptor (CAR) T-cell therapy has revolutionized the approach to patients with relapsed or refractory diffuse large B-cell lymphoma (r/r DLBCL). This study retrospectively analyzed patients treated with commercially available tisagenlecleucel at our hospital and evaluated its safety and effectiveness. Of the 21 patients evaluated, any grade and grade ≥3 cytokine release syndrome (CRS) occurred in 85.7% and 9.5% of the patients, respectively. A total of 66.7% received tocilizumab and 28.6% received glucocorticoids for the treatment of CRS. The complete response (CR) rate at 3 months was 61.9% (95% confidence interval [CI] 38.4-81.9). After a median follow-up of 6.3 months following CAR-T infusion, the progression-free survival (PFS) and overall survival rates at 6 months were 53.1% (95%CI 28.3-72.7) and 69.2% (95%CI 43.7-84.9), respectively. Severe cytopenia and hypogammaglobulinemia occurred frequently following CAR-T infusion. Eight patients (38.1%) had comorbidities that would have made them ineligible for leukapheresis in the JULIET trial. However, the presence of comorbidities at the time of leukapheresis had no significant effect on the rates of CR, PFS, and adverse events. Tisagenlecleucel for r/r DLBCL in the real-world setting showed high efficacy and manageable safety profile comparable with the pivotal trial.

Gene rearrangements of MLL and RUNX1 sporadically occur in normal CD34+ cells under cytokine stimulation.

Gene rearrangements of MLL/KMT2A or RUNX1 are the major cause of therapy-related leukemia. Moreover, MLL rearrangements are the major cause of infant leukemia, and RUNX1 rearrangements are frequently detected in cord blood. These genes are sensitive to topoisomerase II inhibitors, and various genes have been identified as potential fusion partners. However, fetal exposure to these inhibitors is rare. Therefore, we postulated that even a proliferation signal itself might induce gene rearrangements in hematopoietic stem cells. To test this hypothesis, we detected gene rearrangements in etoposide-treated or non-treated CD34+ cells cultured with cytokines using inverse PCR. In the etoposide-treated cells, variable-sized rearrangement bands were detected in the RUNX1 and MLL genes at 3 hours of culture, which decreased after 7 days. However, more rearrangement bands were detected in the non-treated cells at 7 days of culture. Such gene rearrangements were also detected in peripheral blood stem cells mobilized by cytokines for transplantation. However, none of these rearranged genes encoded the leukemogenic oncogene, and the cells with rearrangements did not expand. These findings suggest that MLL and RUNX1 rearrangements, which occur with very low frequency in normal hematopoietic progenitor cells, may be induced under cytokine stimulation. Most of the cells with gene rearrangements are likely eliminated, except for leukemia-associated gene rearrangements, resulting in the low prevalence of leukemia development.

Hematopoietic cell infusion-related adverse events in pediatric/small recipients in a prospective/multicenter study.

BACKGROUND: Hematopoietic cell infusion-related adverse events (HCI-AEs) in hematopoietic stem cell transplantations (HSCTs) have been largely attributed to toxicity of dimethyl sulfoxide (DMSO) for cryopreservation, but HSC products also contain various cells and plasma components. Our recent prospective study of 1125 HSCT recipients revealed the highest overall HCI-AE rate in bone marrow transplantation (BMT) using fresh/noncryopreserved products, although products of peripheral blood stem cell transplantation and cord blood transplantation (CBT) are generally cryopreserved with DMSO containing smaller plasma volumes. We aimed to clarify if product volume and component effects are more substantial in small recipients including children. STUDY DESIGN AND METHODS: We performed subgroup analysis on 219 recipients of 45 kg or less body weight (whole small recipients), including 90 children (pediatric recipients), from the original cohort (general recipients). RESULTS: Whereas overall HCI-AE rates did not differ among hematopoietic stem cell sources in the general recipients, bradycardia most often occurred after CBT in whole small recipients. Conversely, whole small and general recipients shared the same trend of having the highest rate of hypertension in BMT. The overall HCI-AE rate was higher in allogeneic HSCT compared with autologous HSCT. Notably, pediatric recipients showed a 10-fold higher incidence of nausea and vomiting in allogeneic HSCT compared with autologous HSCT, suggesting a possible role of allogeneic antigens. Multivariate analysis identified a relatively large infusion volume per body weight as a significant factor correlating with HCI-AE in whole small recipients. CONCLUSIONS: We should be aware of product volume and specific HCI-AEs such as nausea and vomiting in small patients including children.

[Transfusion-associated circulatory overload with pulmonary alveolar hemorrhage following allogeneic bone marrow transplantation].

A 51-year-old man underwent allogeneic bone marrow transplantation (BMT) for recurrent acute myeloid leukemia. Although the patient developed slight edema, pleural effusion, and cardiac effusion 6 months after BMT, his clinical condition improved with furosemide treatment. The patient was transfused with red blood cells for the management of anemia 8 months after BMT. He developed acute respiratory failure with pulmonary alveolar hemorrhage 80 min after the transfusion. He was diagnosed with transfusion-associated circulatory overload (TACO) due to the presence of acute pulmonary congestion and depressed left ventricular systolic function. Reduced circulatory load due to sufficient furosemide led to ventilator weaning 3 days later. Other causes of pulmonary alveolar hemorrhage were excluded, and the patient's condition improved by cardiac failure treatment only. This clinical course indicated that pulmonary alveolar hemorrhage would breakdown the blood vessels due to acute pulmonary congestion. Chemotherapy and prolonged anemia are high risks for cardiac failure in patients with hematological malignancies. Therefore, the possibility of cardiac failure is considered when patients with hematological malignancies have fluid retention, such as cardiac enlargement, edema, and pleural effusion. Moreover, the body fluids should be monitored before and after blood transfusion.

[Prior harvesting and cryopreservation of peripheral blood stem cells from related donors: current situations in Japan].

Although peripheral blood stem cell (PBSC) transplantations in an unrelated transplant setting have been performed since 2010, prior harvesting and cryopreservation of PBSCs from unrelated donors has not been approved in Japan. There are no restrictions with regard to related donors. Therefore, in April 2015, we conducted a nationwide survey and obtained written answers from 123 transplant hospitals throughout Japan. Our survey revealed that as much as 81.3% of transplant hospitals routinely perform prior harvesting and cryopreservation of PBSCs from related donors and that both cell processing and quality management of cryopreserved products have been appropriately conducted in line with domestic guidelines, although post-thaw quality control and storage period setting require further improvements. Moreover, informed consent obtained from both patients and donors with regard to cryopreservation of PBSCs was not always sufficient in some hospitals. We found that the average number of unused or discarded cryopreserved PBSCs is 1.09 per hospital, and the overall nonuse or discard rates of cryopreserved PBSCs were estimated to be as low as 2.67%.

Severe Hypoxemia in a Healthy Donor for Allogeneic Hematopoietic Stem Cell Transplantation after Only the First Administration of Granulocyte-Colony Stimulating Factor.

BACKGROUND: Granulocyte-colony stimulating factor (G-CSF) is widely used to mobilize peripheral blood stem cells (PBSCs) in healthy donors. A few reports have shown that some healthy donors developed acute respiratory distress syndrome or capillary leak syndrome after more than several rounds of G-CSF administration or leukapheresis. CASE REPORT: We report the case of a healthy donor for allogeneic stem cell transplantation who developed severe hypoxemia 1 h after only the first administration of G-CSF. The donor was administered 10 µg/kg G-CSF (lenograstim) subcutaneously for PBSC mobilization. 1 h after the first administration of G-CSF, the donor suddenly presented with dry cough and dyspnea. The oxygen saturation by pulse oximetry (SpO2) in the room air was 88%. An electrocardiogram and chest radiography revealed no abnormalities. We excluded other causes of severe hypoxemia and diagnosed the donor with hypoxemia due to G-CSF administration, which was subsequently terminated. The donor was administered 2 l/min oxygen via a nasal cannula and 100 mg hydrocortisone intravenously. He subsequently recovered, and SpO2 in the room air returned to 98% 10 h after hypoxemia. CONCLUSION: These respiratory symptoms might be related to anaphylactoid or hypersensitivity reaction. The donors should be observed for at least 1 h after the first administration of G-CSF.

Repeated exposure rather than the total volume of transfused components may influence the incidence of allergic transfusion reactions.

BACKGROUND: The plasma fraction of blood components has an essential role in the etiology of allergic transfusion reactions (ATRs). The difference of incidences of ATRs between fresh-frozen plasma (FFP) and platelet concentrates (PCs), in which plasma is the main component, is not clearly understood. This study compares the frequency of ATRs to FFP versus PCs on both first and subsequent (nonfirst) transfusions and considers the factors influencing the risk of ATRs. STUDY DESIGN AND METHODS: Five hospitals agreed to systematically collect and share 2 years of data (January 2010 through December 2011). This was a retrospective observational analysis of data including the number of transfusion episodes and ATRs for FFP and PCs on first-transfusion patients (without transfusion history) and previously transfused patients. RESULTS: The incidence of ATRs to PCs (2.51%) was significantly higher than to FFP (1.68%) on subsequent transfusions (p < 0.001). On the other hand, there were no significant differences in the incidences of ATRs to FFP (2.67%) and PCs (2.82%) on first transfusions. This discrepancy was most pronounced among males: FFP versus PCs on first transfusions, 2.02% versus 2.60% (p = 0.30); and on subsequent transfusions, 1.58% versus 2.46% (p = 0.0007). Among females, FFP versus PCs on first transfusions was 3.59% versus 3.13% (p = 0.61) and on subsequent transfusions was 1.87% versus 2.61% (p = 0.029). CONCLUSION: Repeated exposure rather than the total volume of transfused components may influence the incidence of ATRs.

Clinical impact of hematogones on outcomes of allogeneic hematopoietic stem cell transplantation.

Increased levels of normal B cell precursors, termed hematogones (HGs), are observed in regenerating bone marrow after chemotherapy or hematopoietic stem cell transplantation (HSCT). Recent reports suggest that emergence of HGs is associated with better outcomes following allogeneic HSCT (allo-HSCT). We reviewed the emergence of HGs and the clinical features of 192 patients after allo-BMT. Patients undergoing allo-BMT from related donors were more likely to develop HGs at day 30 compared to unrelated donors. Furthermore, patients undergoing allo-BMT from HLA-mismatched donors were less likely to develop HGs at day 30. The emergence of HGs at day 30 was an independent prognostic factor among patients who underwent BMT. We found no difference in the relapse rate between HG-positive (+) and HG-negative (-) patients undergoing BMT. HG (-) patients had high non-relapse mortality, grade II to IV acute graft-versus-host-disease (GVHD), fungal infection, and lower IgG levels compared to HG (+) patients. The emergence of HGs at day 30 among patients undergoing BMT may be a very useful indicator of subsequent survival outcomes or acute GVHD in common clinical practice.

Azacitidine and gemtuzumab ozogamicin as post-transplant maintenance therapy for high-risk hematologic malignancies.

Disease recurrence remains the principal cause of treatment failure after allogeneic hematopoietic stem cell transplantation. Post-transplant maintenance therapy with azacitidine (AZA) is promising to prevent relapse but the outcomes are unsatisfactory in patients at high risk of recurrence. Herein, we evaluated the outcome in patients who received AZA and gemtuzumab ozogamicin (GO), anti-CD33 antibody-calicheamicin conjugate, as post-transplant maintenance therapy. Twenty-eight patients with high-risk hematologic malignancies harboring CD33-positive leukemic blasts received the maintenance therapy. AZA (30 mg/m2) was administered for 7 days, followed by GO (3 mg/m2) on day 8. The maximum number of cycles was 4. At transplant, 21 patients (75.0%) had active disease. Their 2-year overall survival, disease-free survival, relapse, and non-relapse mortality rates were 53.6%, 39.3%, 50.0%, and 10.7%, respectively. Of these patients, those with minimal residual disease at the start of maintenance therapy (n = 9) had a higher recurrence rate (66.7% vs. 42.1% at 2 years, P = 0.069) and shorter disease-free survival (11.1% vs. 52.6% at 2 years, P = 0.003). Post-transplant maintenance therapy with AZA and GO was generally tolerable but more than half of the patients eventually relapsed. Further improvements are needed to prevent relapse after transplantation in patients with high-risk hematologic malignancies.

Early failure is still a poor prognostic factor in patients with relapsed or refractory large B-cell lymphoma in the era of CAR T-cell therapy.

Patients with refractory or relapsed (R/R) large B-cell lymphoma (LBCL) refractory to first-line chemotherapy or with early relapse have poor outcomes. While chimeric antigen receptor (CAR) T-cell therapy has impressive efficacy after two or more lines of chemotherapy, it's still uncertain if these outcomes remain consistent in the context of third-line CAR T-cell therapy. We conducted a retrospective study of 107 R/R LBCL patients. Patients with relapse 12 months or more after their first-line chemoimmunotherapy (late failure: n = 25) had significantly longer overall survival (OS) than patients with refractory disease or relapse within 12 months (early failure: n = 82) (median OS: not achieved vs. 18.4 months; P < 0.001). Among patients who proceeded to autologous hematopoietic stem-cell transplantation (auto-HSCT), those with late failure had significantly longer event-free survival (EFS) than those with early failure (median EFS: 26.9 vs. 3.1 months; P = 0.012). However, no significant difference in EFS was detected among patients who underwent CAR T-cell therapy (median EFS: not reached vs. 11.8; P = 0.091). Cox regression with restricted cubic spline demonstrated that timing of relapse had significant impact on EFS in patients with auto-HSCT but not in patients with CAR T-cell therapy. Of patients who were scheduled for CAR T-cell therapy, those with late failure were significantly more likely to receive CAR T-cell therapy than those with early failure (90% vs. 57%; P = 0.008). In conclusion, patients with early failure still experienced poor outcomes after the approval of third-line CAR T-cell therapy.

Impact of gene alterations on clinical outcome in young adults with myelodysplastic syndromes.

Young adults with myelodysplastic syndrome (MDS) are rare, and the clinical significance of driver mutations has not yet been analysed. We analysed the gene mutations and copy number alterations (CNAs) in younger MDS patients using next-generation sequencing, targeting 68 genes that were recurrently mutated in myeloid malignancies, to investigate the correlation between their genetic alterations and clinical outcomes. We enrolled 55 patients retrospectively (aged < 50 years). At least one mutation was detected in 56% of the patients. The most frequently mutated genes were ASXL1 and RUNX1, 13% each. We defined higher-risk patients as those with ≥ 2 mutations, except for SF3B1 mutation, and/or CNA. The 3-year overall survival (OS) in patients with a higher-risk was lower than that in those with a lower-risk (50.8% vs. 71.8%, P = 0.024). Among the 44 transplant recipients, patients with higher-risk had a significantly lower OS and tended to have a higher cumulative incidence of relapse (CIR) than those with a lower-risk (3-year OS: 38.0% vs. 64.4%, P = 0.039; 3-year CIR: 44.0% vs. 24.1%, P = 0.076). Our results showed that genetic aberrations can predict clinical outcomes in younger MDS patients, despite the low rate of genetic mutations.

Case report: Immune pressure on hematopoietic stem cells can drastically expand glycosylphosphatidylinositol-deficient clones in paroxysmal nocturnal hemoglobinuria.

Introduction: Paroxysmal nocturnal hemoglobinuria (PNH) is a rare hematological disease characterized by intravascular hemolysis, thrombosis, and bone marrow (BM) failure. Although PNH is caused by excessive proliferation of hematopoietic stem cell (HSC) clones with loss of function mutations in phosphatidylinositol N-acetylglucosaminyltransferase subunit A (PIGA) genes, what drives PNH clones to expand remains elusive. Case description: We present a case of a 26-year-old female who presented with hemolytic anemia, thrombocytopenia, and leukopenia. Flow cytometry analysis of peripheral blood showed that 71.9% and 15.3% of the granulocytes and erythrocytes were glycosylphosphatidylinositol-anchored protein deficient (GPI[-]) cells. The patient was diagnosed with PNH with non-severe aplastic anemia. Deep-targeted sequencing covering 390 different genes of sorted GPI(-) granulocytes revealed three different PIGA mutations (p.I69fs, variant allele frequency (VAF) 24.2%; p.T192P, VAF 5.8%; p.V300fs, VAF 5.1%) and no other mutations. She received six cycles of eculizumab and oral cyclosporine. Although the patient's serum lactate dehydrogenase level decreased, she remained dependent on red blood cell transfusion. Six months after diagnosis, she received a syngeneic bone marrow transplant (BMT) from a genetically identical healthy twin, following an immune ablative conditioning regimen consisting of cyclophosphamide 200 mg/kg and rabbit anti-thymocyte globulin 10 mg/kg. After four years, the patient's blood count remained normal without any signs of hemolysis. However, the peripheral blood still contained 0.2% GPI (-) granulocytes, and the three PIGA mutations that had been detected before BMT persisted at similar proportions to those before transplantation (p.I69fs, VAF 36.1%; p.T192P, VAF 3.7%; p.V300fs, VAF 8.6%) in the small PNH clones that persisted after transplantation. Conclusions: The PNH clones that had increased excessively before BMT decreased, but persisted at low percentages for more than four years after the immunoablative conditioning regimen followed by syngeneic BMT. These findings indicate that as opposed to conventional theory, immune pressure on HSCs, which caused BM failure before BMT, was sufficient for PIGA-mutated HSCs to clonally expand to develop PNH.