A 60-year-old woman with myelodysplastic syndrome/myeloproliferative neoplasm-unclassifiable underwent unrelated bone marrow transplantation from a human leukocyte antigen (HLA) 8/8 allele-matched male donor. Neutrophil engraftment was achieved on day 29. Fluorescence in situ hybridization of sex chromosomes demonstrated complete donor chimerism. The red blood cell and platelet transfusion dependence continued, and the neutrophil count decreased gradually. Despite prolonged administration of broad-spectrum antibiotics for febrile neutropenia, blood cultures on days 46 and 58 returned positive for Stenotrophomonas maltophilia (SM). Contrast-enhanced computed tomography revealed multiple nodules of septic emboli in the lungs and kidneys, suggesting a disseminated SM infection. Antibiotic therapy was conducted based on antimicrobial susceptibility testing. However, the blood cell count failed to normalize and a secondary graft failure was diagnosed. A HLA-haploidentical peripheral-blood stem-cell transplantation from the patient’s son was performed on day 134 after the initial transplantation. Neutrophil engraftment was achieved on day 11. Red blood cells and platelets were also engrafted. After the resolution of the SM bacteremia, the patient was discharged on day 63. The prognosis of the SM bacteremia with neutropenia is poor. Antibiotic treatment based on antimicrobial susceptibility testing and a second transplant from an HLA-haploidentical donor likely contributed to the successful outcome in this patient.

A 28-year-old male patient presented with multiple lymphadenopathies and extranodal masses. He was diagnosed with stage IVB ALK-positive anaplastic large cell lymphoma after the right axillary lymph node biopsy. A partial metabolic response with fluorodeoxyglucose accumulation was observed in the residual disease of the upper left hilar lymph node after eight courses of brentuximab vedotin, cyclophosphamide, adriamycin, and prednisolone. We started alectinib at 600 mg daily, which achieved a complete metabolic response (CMR) after three months. The CMR was maintained and alectinib was continuously administered without adverse events at the last follow up. Alectinib showed high efficacy and tolerability, though the optimal period and long-term adverse effects of administration remain unclear. Therefore, further studies are necessary.

This report describes a 56-year-old man who was diagnosed with myeloid sarcoma (MS) of the testis and right shoulder after receiving allogenic stem cell transplantation (allo-SCT) at the age of 47 for acute myeloid leukemia (AML) with inv (16) (p13.1;q22). Nine years after allo-SCT, he complained of a painful right testicular mass. He underwent orchiectomy, and the pathologic diagnosis was MS. Inv (16) was identified by fluorescence in situ hybridization (FISH) using testicular tumor specimens. 18F-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) revealed FDG accumulation in the right shoulder. FISH analysis of bone marrow aspirate revealed no increase in blasts and ruled out CBFB-MYH11 fusion. Reinduction chemotherapy, consolidation, and local radiation therapy for the left testis and right shoulder were administered to him. After that, he received a second allo-SCT from an unrelated donor who was HLA-matched. As of 2 years after the second allo-SCT, recurrence of neither AML nor myeloid sarcoma has been observed. The recurrence of MSs without bone marrow involvement is frequently reported in single, multiple single organs, or multiple single regions. Even if MSs recur in a distant location, combining systemic and local treatment may be a better treatment strategy.

An 80-year-old Japanese male patient presented to our hospital with complaints of fatigue. His peripheral blood tests revealed pancytopenia with predominant lymphocytes and without blasts. The bone marrow (BM) aspiration was unsuccessful due to a dry tap, and the subsequent BM biopsy revealed hypocellular marrow with fibrosis. He was diagnosed with myelodysplastic syndrome (MDS) with excess blasts (EB)-2 based on CD34-positive cells. The chromosome analysis of the BM revealed monosomy 7, and the SAMD9 W22^* mutation was detected (variant allele frequency [VAF] of 51.22%) using next-generation sequencing. An identical mutation was observed in the buccal mucosa (VAF of 50%), which was confirmed as a germline mutation. The SAMD9 gene mutation is reported as one of the causative genes for MIRAGE syndrome and child-onset MDS. The present case was considered a loss-of-function mutation due to the near full-length SAMD9 deletion. This is the first adult case of MDS with SAMD9 W22^* as a germline mutation.

Bing-Neel syndrome (BNS) is a rare disease manifestation of Waldenström’s macroglobulinemia characterized by abnormal lymphoplasmacytoid cells infiltration of the central nervous system. In September 2019, a 46-year-old man presented to a previous hospital with hand tremors, nausea, and dysuria. Demyelination of cerebral white matter and the spinal cord was discovered using MRI. Steroid pulse therapy was used to treat inflammatory demyelinating disease, and it provided temporary relief, but the symptoms returned when the steroids were stopped. He was referred to our hospital in June 2020, for further evaluation with the possibility of hematological malignancy. BNS was diagnosed based on the presence of abnormal lymphoplasmacytoid cells in the bone marrow and cerebrospinal fluid (CSF), as well as the presence of the MYD88^L265P mutation in the CSF specimen. In July 2020, BR (bendamustine, rituximab) therapy was administered, but it was ineffective. Oral administration of tirabrutinib, which was recently approved for WM, began in August 2020. He has achieved long-term remission and steroid withdrawal, with no notable side effects. This is the second report of successful treatment of BNS with tirabrutinib. More research is needed to confirm tirabrutinib’s efficacy in the treatment of BNS.

We examined the incidence and clinical features of thyroid dysfunction in 661 patients who received allogeneic hematopoietic stem cell transplantation (allo-HSCT) in our hospital. At a median of 2.5 (1.0-11.3) years, 28 patients (4.2%) developed subclinical hypothyroidism, and 16 patients (2.4%) developed hypothyroidism. Eight of 16 patients (50%) with hypothyroidism were positive for anti-thyroid antibodies. Ten of 44 patients (22.7%) with thyroid dysfunction were discovered more than 5 years after allo-HSCT. Thyroid dysfunction with late onset was common in allo-HSCT recipients, and thyroid function should be monitored on a regular basis.

Deep sequence analysis for BCR-ABL revealed that native BCR-ABL decreased slowly after an exponential decrease within three months of tyrosine kinase inhibitor (TKI) treatment. BCR-ABL^Ins35bp was present at diagnosis and increased to account for 15-30% of total BCR-ABL when IS BCR-ABL was reduced to 1%. Native BCR-ABL and BCR-ABL^Ins35bp correspond to early relapse and fluctuating minimal residue disease, respectively, in the STOP-TKI trial. These findings highlight the clinical significance of quantifying BCR-ABL^Ins35bp. We discovered pseudosplice sites at both ends of 35 bp within ABL intron 8, and TKI off-target effect inhibited RNAPII S2P and reduced native BCR-ABL expression but induced BCR-ABL^Ins35bp mis-splicing.

Acquired pure red cell aplasia (PRCA) develops in a variety of contexts and thus, should be regarded as a syndrome. The three major subtypes of acquired PRCA are idiopathic PRCA, T cell large granular lymphocytic leukemia (T-LGLL)-associated PRCA, and thymoma-associated PRCA. Although the Japanese National Research Group on Idiopathic Bone Marrow Failure Syndromes of the Ministry of Health, Labor and Welfare of Japan has made significant contributions to our understanding of PRCA, details of its clinical characteristics, and pathophysiological mechanisms remain largely unknown. A recent epidemiological analysis using the JSH Hematologic Disease Registry revealed that approximately 100 new cases with acquired PRCA were diagnosed annually in Japan, which was higher than previously thought to be. The median age of the patients was 73 years. A prospective observational study on chronic PRCA (PRCA2016) is currently ongoing, and it may provide new clinical insights into acquired PRCA. Dysregulation of T cells has been shown to play a central role in PRCA. We studied T cell clonalities and STAT3 mutations in 90 PRCA patients and discovered that clonal T cell expansions were frequently recognized and closely associated with STAT3 mutations in the three major types of PRCA.

Human leukocyte antigen (HLA) class I allele-lacking [HLA (−)] leukocytes provide compelling evidence that cytotoxic T-lymphocytes are involved in the development of aplastic anemia (AA). However, the clinical significance and precise mechanisms underlying clonal hematopoiesis by HLA (−) hematopoietic stem progenitor cells remain unknown. In HLA (−) cells from patients with AA, we discovered a common nonsense mutation at codon19 (c.19C>T, p.R7X) in exon1 (Exon1^mut) of different HLA-A and HLA-B alleles. Exon1 mutation detection using droplet digital polymerase chain reaction (ddPCR) is a powerful tool for diagnosing immune pathophysiology in patients with bone marrow failure. We also looked at the prognosis of 633 patients with AA, including 127 with HLA (−) leukocytes who had been followed up for a long time. In Japanese patients with AA, HLA (−) leukocytes and concomitant aberrant clones were not associated with clonal evolution to MDS/AML. In patients with AA and both marker (−) leukocytes, HLA (−) leukocytes may indicate a lower risk of developing secondary paroxysmal nocturnal hemoglobinuria (PNH). Detecting HLA (−) leukocytes is critical for managing patients with AA and assisting physicians in selecting appropriate therapy.

Hematopoietic stem cells (HSCs) possess multilineage differentiation capability, which sustains the production of blood and immune cells throughout life. However, the precise mechanisms by which HSCs initiate differentiation toward a particular lineage and the factors that attenuate their lymphopoietic potential with aging are yet to be elucidated. Our group has investigated this issue for over two decades. We initially developed a method for segregating early lymphoid progenitors from HSCs and identified two molecules: endothelial cell-selective adhesion molecule (ESAM), highly expressed in HSCs, and special AT-rich sequence binding protein 1 (SATB1), expressed in early lymphoid progenitors. ESAM marks HSCs across species, including humans. In addition to its significance in stress-induced hematopoiesis, ESAM is also useful in identifying features of human acute myeloid leukemia stem cells. Further, we determined the role of SATB1 in the early HSC differentiation processes toward the lymphoid lineage. Remarkably, SATB1 expression in HSCs significantly decreased with aging, whereas its exogenous induction in aged HSCs rejuvenated their lymphopoietic potential. Furthermore, SATB1-expressing HSCs demonstrated robust lymphopoietic and long-term reconstituting capability, whereas HSCs without SATB1 skewed toward the myeloid lineage. Thus, our continuing research has revealed the significance of ESAM and SATB1 in the fundamental biology of HSCs.

Hematopoietic stem cells (HSCs) are tissue-specific stem cells that are critical for homeostasis and regeneration of the hematopoietic system. Multiple mechanisms exist that help maintain the size and integrity of the HSC pool after exposure to various insults to provide all lineages of blood cells throughout life. Clonal hematopoiesis, an age-related clonal mosaicism detected in the hematopoietic system and governed by aberrant HSC clones with somatic mutations, has recently been identified as an important risk factor for hematological malignancy and cardiovascular disease. Cells with a somatic mutation can present neoantigens via the major histocompatibility complex and can be recognized and eliminated by antigen-specific T cells. However, whether this mechanism also acts to maintain HSC pool integrity remains largely unclear. In this review, I have summarized mechanisms known to support the lifelong maintenance of HSC numbers and function, introduced recent findings that indicate active interaction between HSCs and T cells, and discussed potential effects of its dysregulation on hematological diseases.

After a long-term hospitalization following a ski accident in college, I decided to choose a specialty in hematology and oncology. In graduate school, after learning the basics of biostatistics and the methodology of clinical trials, I had the opportunity to go through a series of clinical trial tasks, from launching to writing a clinical study report, which led to the study drug approval. This has greatly motivated me to be actively involved in this field. At the Dana-Farber Cancer Institute, I studied outcomes research under a supervisor, and at a time of difficulty, my good role model, Dr. Stephanie Lee, had urged me, saying, “That which does not kill you makes you stronger.” Subsequently, I devoted myself to the establishment of a data center for a Japanese pediatric leukemia/lymphoma study group, currently a subcommittee of the Japan Children’s Cancer Group, and to develop an academic research organization for conducting ICH-GCP-compliant international clinical trials, including the originally developed EDC system. I was struggling in balancing work and parenting. Fortunately, I was supported by my encounters with respectable people.

The female physician career symposium entitled “Thinking about the Careers of Diverse Female Physician” was held at the 2021 annual meeting. Herein, I introduced my carrier not only to female but also male physicians to establish their unique original carrier path and recognize their worth of existence. Until reaching the final goal of your research and job, you will always be in an uphill course with some valley to be overcome by efforts. Similarly, life is always uphill, and the time of marriage and child-rearing is inevitably a valley to be filled with support by your environment and originality to appeal to the worth of existence.