Haematopoietic regeneration by HLA-A*0206-deficient clones in severe aplastic anaemia without definitive immunosuppressive treatment.

We describe the case of a 74-year-old man with severe aplastic anaemia who experienced persistent remission attributed to proliferation of HLA allele-deficient clones. Despite an initial worsening of pancytopenia with eltrombopag and ciclosporin treatment, gradual trilineage haematopoietic recovery occurred, with blood counts normalizing over 3 years. Flow cytometry and deep nucleotide sequencing revealed that haematopoiesis was primarily supported by several clones with somatic mutations that inactivated antigen presentation via HLA-A*0206. This suggests that monitoring haematopoietic regeneration by immune escape clones could be an alternative approach for immune aplastic anaemia patients who possess HLA allele-deficient clones and cannot tolerate standard therapy.

The effectiveness of immunosuppressive therapy in patients with aplastic anaemia secondary to chemoradiotherapy for cancers.

The outcome of immunosuppressive therapy (IST) and prognosis in patients with aplastic anaemia (AA) secondary to chemotherapy or radiotherapy for cancers remains unknown. A total of 43 of 2559 patients with AA referred to our hospital had previously received chemoradiotherapy for various types of solid tumours (n = 25) or haematological malignancies (n = 18). Their cancer status was complete remission (CR) in 27, non-CR in 13, and unknown in three. Small populations of glycosylphosphatidylinositol-anchored protein-deficient [GPI(-)] granulocytes were detected in 16 patients (37·2%). Of 18 patients who were treated with IST, 50% improved regardless of the presence of GPI(-) cells. The overall survival (OS) rate was significantly higher in patients with a history of solid tumours patients than in those of haematological malignancies (median OS, 87 vs. 11 months, P = 0·0003), and in patients treated with IST than in those of untreated patients (median OS, 115 vs. 20 months, P = 0·028). Cancer aggravation occurred in two of four patients who were treated with IST while in non-CR of their original cancers. Progression to myelodysplastic syndromes was observed in two patients not possessing GPI(-) cells. IST should thus be considered for patients with AA secondary to chemoradiotherapy for cancers, particularly when their original solid tumours are in CR.

A frequent nonsense mutation in exon 1 across certain HLA-A and -B alleles in leukocytes of patients with acquired aplastic anemia.

Leukocytes that lack HLA allelic expression are frequently detected in patients with acquired aplastic anemia (AA) who respond to immunosuppressive therapy (IST), although the exact mechanisms underlying the HLA loss and HLA allele repertoire likely to acquire loss-of-function mutations are unknown. We identified a common nonsense mutation at position 19 (c.19C>T, p.R7X) in exon 1 (Exon1mut) of different HLA-A and -B alleles in HLA-lacking granulocytes from AA patients. A droplet digital PCR (ddPCR) assay capable of detecting as few as 0.07% Exon1mut HLA alleles in total DNA revealed the mutation was present in 29% (101/353) of AA patients, with a median allele frequency of 0.42% (range, 0.071% to 21.3%). Exon1mut occurred in only 12 different HLA-A (n=4) and HLA-B (n=8) alleles, including B*40:02 (n=31) and A*02:06 (n=15), which correspond to 4 HLA supertypes (A02, A03, B07, and B44). The percentages of patients who possessed at least one of these 12 HLA alleles were significantly higher in the 353 AA patients (92%, P.

[A loss-of-function mutation in exon1 of limited HLA class I alleles is common in patients with aplastic anemia].

Leukocytes that lack HLA allelic expression (HLA-LLs) caused by a copy-number-neutral loss of heterozygosity in the short arm of chromosome 6 (6pLOH) and somatic mutations in HLA class I genes are commonly identified in patients with acquired aplastic anemia (AA), although the exact mechanisms underlying the HLA loss and HLA class I allele repertoire likely to acquire loss-of-function mutations remain unknown due to the limited number of AA patients that have been studied for loss-of-function mutations in HLA class I genes. We identified a common nonsense mutation at codon19 (c.19C>T, p.R7X) in exon1 (Exon1mut) of different HLA-A and HLA -B alleles in HLA-LLs from AA patients. Screening of 353 Japanese patients with AA using a novel droplet digital PCR assay revealed Exon1mut in 101 (29%) of the patients. Exon1mut occurred in only 12 different HLA-A (n=4) and HLA-B (n=8) alleles that corresponded to 4 HLA supertypes (A02, A03, B07, and B44), suggesting that limited autoantigens presented by these HLA class I alleles to T cells are involved in AA development. These findings provide insight into the immune pathophysiology of BM failure and contribute to identify candidate autoantigens in AA.

Familial immune-mediated aplastic anaemia in six different families.

We studied the pathophysiology of aplastic anaemia (AA) in six different pairs of relatives without a family history of hematologic disorders or congenital AA. Five and four of the six pairs shared the HLA-DRB1*15:01 and B*40:02 alleles, respectively. Glycosylphosphatidylinositol-anchored protein-deficient blood cells were detected in eight of the 10 patients evaluated. In a mother-daughter pair from one family, flow cytometry detected leukocytes lacking HLA-A2 due to loss of heterogeneity in chromosome 6p. Whole-exome sequencing of the family pair revealed a missense mutation in MYSM1. These results suggest that genetic inheritance of immune traits might underlie familial AA in some patients.

Outcomes after allogeneic hematopoietic stem cell transplantation in acute myeloid leukemia patients with der(1;7)(q10;p10).

The prognosis of acute myeloid leukemia (AML) patients with der(1;7)(q10;p10) who underwent allogeneic hematopoietic stem cell transplantation (allo-SCT) is unclear due to its rarity. We retrospectively analyzed 151 AML patients with der(1;7)(q10;p10) and compared the findings with those of 853 AML patients with monosomy 7 or chromosome 7q deletion (-7/del(7q)) using Japanese nationwide registry data. The der(1;7)(q10;p10) group showed significantly better transplant outcomes than the -7/del(7q) group. In the multivariate analysis of the der(1;7)(q10;p10) group, additional chromosomal abnormalities and a poor performance status significantly influenced the survival. In conclusion, allo-SCT is a feasible treatment option for AML patients with der(1;7)(q10;p10).

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.

Hematopoietic stem progenitor cells lacking HLA differ from those lacking GPI-anchored proteins in the hierarchical stage and sensitivity to immune attack in patients with acquired aplastic anemia.

To characterize glycosylphosphatidylinositol-anchored protein-deficient (GPI[-]) and HLA-class I allele-lacking (HLA[-]) hematopoietic stem progenitor cells (HSPCs) in acquired aplastic anemia (AA), we studied the peripheral blood (PB) of 56 AA patients in remission who possessed both (n = 13, Group A) or either GPI(-) (n = 34, Group B) and HLA(-) (n = 9, Group C) cell populations. Seventy-seven percent (10/13) of Group A had HLA(-) cells in all lineages of PB cells, including platelets, while only 23% (3/13) had GPI(-) cells in all lineages, and the median percentage of HLA(-) granulocytes in the total granulocytes (21.2%) was significantly higher than that of GPI(-) granulocytes (0.28%, P < 0.05). The greater lineage diversity in HLA(-) cells than in GPI(-) cells was also seen when Group B and Group C were compared. Longitudinal studies of seven patients in Group A showed a gradual decrease in the percentage of HLA(-) granulocytes, with a reciprocal increase in the GPI(-) granulocytes in four patients responding to cyclosporine (CsA) and an increase in the HLA(-) granulocytes with a stable or declining GPI(-) granulocytes in three patients in sustained remission off CsA therapy. These findings suggest that HLA(-) HSPCs differ from GPI(-) HSPCs in the hierarchical stage and sensitivity to immune attack in AA.

Resolution of Epstein-Barr virus-associated hemophagocytic lymphohistiocytosis associated with rapid immune reconstruction after a single course of CHOP therapy.

Epstein-Barr virus-associated hemophagocytic lymphohistiocytosis (EBV-HLH) is a life-threatening disease characterized by the uncontrolled proliferation of EBV-infected T/NK cells with resultant immune system failure against EBV. While a CD5-HLA-DR+CD8+ T-cell population was previously shown to be EBV-infected cells and a useful marker for monitoring the response to treatment of EBV-HLH, changes in other lymphocyte subsets associated with EBV-HLH treatments have not been closely studied. We herein report a 25-year-old woman with EBV-HLH who presented with a fever, liver failure, and pancytopenia. CD8+ T cells harbored EBV. After failing steroid pulse therapy, one course of CHOP therapy immediately improved her fever and laboratory data and reduced the population of EBV-infected cells. Although the number of EBV-infected cells increased on day 20 of CHOP, a sharp increase in NK cells and normal activated T cells ensued, and the infected cells disappeared without an additional CHOP cycle. She has maintained remission without complications. This rapid immune reconstitution has not been observed in two other patients treated with HLH-2004 protocol-like regimens including prolonged immunosuppressants and etoposide. One cycle of CHOP was thought to have induced the resolution of EBV-HLH by eliminating infected cells as well as inducing the reconstruction of anti-EBV immunity.

Osteosarcoma Manifesting Systemic Inflammation and Histological Features Mimicking Plasma Cell-type Castleman Disease.

A 73-year-old man was referred to our hospital with a persistent fever, anemia, and a mass in the left pubic region. The findings of biopsy evaluations of the mass and a left inguinal lymph node were consistent with Castleman disease (CD) of plasma cell type. His serum interleukin 6 (IL-6) level was remarkably elevated, supporting the diagnosis of CD. However, imaging analyses revealed destruction of the pubic bone by the mass, which was atypical for CD. Therefore, another deeper biopsy was performed, which finally led to the diagnosis of IL-6-producing osteosarcoma. We conclude that clinicians should carefully exclude malignancies prior to making a CD diagnosis.