Although Pneumocystis pneumonia (PCP), a life-threatening infection, has been reported in patients with non-Hodgkin B-cell lymphoma (BNHL) who were treated with rituximab-containing chemotherapies (R-CTX), the PCP prophylaxis regimen awaits establishment to date. This study reports a retrospective analysis of the efficacy and safety of a low-dose trimethoprim/sulfamethoxazole (TMP/SMX) in patients with BNHL receiving R-CTX. We retrospectively analyzed 156 patients newly diagnosed with BNHL who received R-CTX at our institute from 2010 to 2015. We collected patients’ clinical and laboratory data, including lymphocytes count, IgG level, PCP prophylaxis regimens, and adverse events (AEs). Patients were categorized into the following two groups based on the TMP/SMX regimen: group A (33 patients; 80 mg/400 mg×3/week) or group B (65 patients; 160 mg/800 mg×2/week). Both lymphocytes count and IgG level declined during R-CTX. No patient developed PCP. Patients in group B exhibited a significantly higher incidence of AEs (18.2% vs. 63.1%; p<0.05) and increased AST (6.1% vs. 26.6%; p<0.05), compared with those in group A. Thus, TMP/SMX (80 mg/400 mg×3/week) effectively prevents PCP and is preferable because of the lower rates of AEs.

A 66-year-old male presented with fever and erythema at our hospital, and leukoerythroblastosis, anemia, thrombocytopenia, and multiple low-density lesions in the moderately enlarged spleen were detected. Skin tissue revealed CD8⁺ T cells with the expression of cytotoxic molecule markers involving fat lobules, and subcutaneous panniculitis T-cell lymphoma (SPTCL) was diagnosed. The bone marrow displayed no infiltration of lymphoid tumor cells, but hyperplasia of granulocytes and megakaryocytes with grade 2 stromal fibrosis. In addition, the bone marrow exhibited diffuse ¹⁸F-fluorodeoxyglucose (FDG) accumulation on FDG positron-emission tomography/computed tomography (FDG-PET/CT). Although chemotherapy improved SPTCL, the patient died from leukocytosis with leukoerythroblastosis. We obtained negative results for the JAK2 V617F mutation, and CD34⁺ cells were elevated in the bone marrow compared with the levels at initial examination. The final diagnosis was concurrent myelodysplastic syndrome (MDS) with fibrosis and SPTCL. This report highlights that it is essential to consider MDS or other myeloproliferative neoplasms (MPN) as possible complications when malignant lymphoma complicates myelofibrosis in the absence of bone marrow infiltration of lymphoma cells. Perhaps, the assessment of clonal markers of MPN and FDG accumulation patterns in the bone marrow by FDG-PET/CT could enable differentiation.

Here, we report the case of a 9-year-old girl with acute myeloid leukemia (AML) developed from systemic mastocytosis (SM). She experienced bladder and rectal disturbance due to an extramedullary nodule in the paraspinal region of the sacrum. Cytogenetic and genetic analyses of leukemic cells revealed the KIT D816Y mutation besides t (8;21) (q22:q22) /RUNX1-RUNX1T1. Despite receiving proton beam therapy after conventional chemotherapy, the patient relapsed after 2 months. As SM-AML with the KIT D816 mutation in adults exhibits a poor prognosis, hematopoietic stem cell transplantation is recommended. Owing to a few reports of SM-AML in children, the standard therapy for pediatric cases has not been established to date. Based on our experience and the related literature, the prognosis of childhood SM-AML could be as poor as in adults. Hence, further investigation, including mutational analyses of the KIT gene, is warranted to establish a risk-oriented strategy for managing childhood SM-AML.

Although sickle cell disease (SCD) is common in endemic areas of malaria, it is one of the rare diseases in Japan. Hence, SCD and its complications are not well established in Japan. An 11-year-old girl was referred to the specialized pediatric center of our hospital. She was born in Brazil and diagnosed with SCD after birth. However, she did not have a routine checkup in Japan. Owing to influenza viral infection, she developed vaso-occlusive pain crisis (VPC) and needed hospitalization for pain management. After admission, she developed dyspnea, needing intratracheal intubation and mechanical ventilation. A chest X-ray revealed bilateral pulmonary infiltration, suggesting acute chest syndrome (ACS) complicated with SCD. Intensive care, including transfusion of red blood cells, successfully improved her condition. Reportedly, half cases of VPC develop ACS, and the mortality of ACS is very high. Hence, when managing VPC cases, the prevention of ACS, through transfusion of red blood cells or infectious control, is imperative. Thus, Japanese hematologists and pediatricians should recognize SCD and its complications owing to an anticipated increase of foreign travelers or migrants in the future.

A 47-year-old male was admitted to our hospital because of left hypochondrium part pain and was diagnosed with splenomegaly with splenic infarctions in May 2016. His complete blood cell count was almost within normal limits, and a bone marrow biopsy revealed normal cellularity with no fibrosis. In addition, no abnormal uptake was noted on FDG PET/CT. In August 2016, he underwent splenectomy for splenomegaly. The histological examination revealed fibrotic stenosis of the blood vessels in the spleen. After splenectomy, his platelet count elevated and remained at >1,000×10⁹/l 3 months later. Finally, he was diagnosed with latent essential thrombocythemia (ET) because the JAK2V617F mutation was positive. Accordingly, oral hydroxyurea was initiated. Thrombosis could be a complication in myeloproliferative neoplasms (MPN). In our case, ET was masked, perhaps, because of hypersplenism and splenomegaly because of splenic vein thrombosis. Hence, examination of the JAK2V617F mutation in patients with splanchnic vein thrombosis is recommended because of the possibility of latent MPN.

Distinguishing between IgG4-related disease (IgG4-RD) and hyper-interleukin (IL) -6 syndrome, such as immune mediated conditions, autoimmune diseases, and idiopathic multicentric Castleman disease (iMCD) is challenging. Here, we report the case of a 69-year-old man with cervical lymphadenopathy who was admitted to our hospital and histologically diagnosed with hyper-IL-6 syndrome mimicking IgG4-RD phenotypically. Laboratory data detected polyclonal hypergammaglobulinemia comprising IgG, including IgG4 (2,350 mg/dl). Computed tomography revealed presence of systemic lymphadenopathy, enlarged bilateral submandibular glands, and infiltrative shadow in the right lower lung. Magnetic resonance imaging revealed diffusely enlarged pancreas the size of a sausage and hypointense rim on T2, suggesting autoimmune pancreatitis as part of IgG4-RD. Biopsy of the cervical lymph node revealed proliferation of IL-6-positive mature plasma cells in the expanded interfollicular area with an elevated IgG4+/IgG+ cell ratio (approximately 70%). These histological findings were consistent with hyper-IL-6 syndrome rather than IgG4-RD; however, the serum IL-6 level was slightly elevated. Bone marrow aspiration detected both IgG4- and IL-6-positive mature plasma cells. Although this case cannot be diagnosed as IgG4-RD because it failed to meet its diagnostic criteria, administration of oral prednisolone (0.5 mg/kg) resulted in rapidly improved lymphadenopathy, enlarged pancreas, and serological findings. This report can be helpful for the diagnostic assessment of polyclonal hypergammaglobulinemia conditions.

A 48-year-old male underwent an osteosynthesis surgery for right patellar fracture without bleeding episodes around the surgery. After 7 months, he presented with a bleeding episode after a nail extraction surgery from his knee joint. He was diagnosed with mild hemophilia A after his second surgery. The patient’s clinical course suggested that he had mild hemophilia A, although he had a past surgical history without any bleeding episodes. Early diagnosis is important in patients with mild hemophilia A because bleeding episodes complicated with surgery can be prevented by the administration of prophylactic replacement therapy.

Fanconi anemia (FA) is a genetic disorder characterized by progressive bone marrow failure, increased susceptibility to leukemia and cancer, and genomic instabilities. Protein products encoded by 22 FA genes, identified till date, cooperate in a molecular pathway called the FA pathway to repair DNA interstrand cross-links induced by chemotherapeutic agents, such as mitomycin C and cisplatin. An accumulating number of studies have shown several new functional aspects of the FA pathway, particularly in the context of the pathogenesis of bone marrow failure. This review focuses on the following topics: (1) aldehydes as intrinsic interstrand cross-linkers; (2) cytokine-induced hematopoietic stress; (3) increased transforming growth factor-β signaling; (4) mitochondrial functions of FA proteins. These findings are expected to offer new therapeutic opportunities for bone marrow failure in FA.

Sideroblastic anemia (SA) signifies a group of heterogeneous congenital and acquired disorders characterized by anemia and the presence of ring sideroblasts in the bone marrow. Congenital SA is a rare disease caused by mutations of genes involved in heme biosynthesis, iron-sulfur cluster biosynthesis, and mitochondrial protein synthesis. In addition, SA can occur after exposure to certain drugs or alcohol and because of copper deficiency (secondary SA). Of note, SA also correlates with myelodysplastic syndrome (idiopathic SA). Recent progress in the genome analysis technology has enabled the identification of novel causative genes for SA, elucidating the molecular pathophysiology of these disorders. Accordingly, the significance of genetic diagnosis for SA has been increasing. This review discusses the current understanding of genetic mutations involved in the pathophysiology of SA.

Acquired aplastic anemia (AA) is a hematopoietic disorder caused by an immunologic attack on hematopoietic stem cells (HSCs). The presence of cells with a paroxysmal nocturnal hemoglobinuria (PNH) phenotype or with copy-number neutral loss of heterozygosity of chromosome 6p (6pLOH) suggests an immune-mediated pathophysiology underlying AA. Recently, genomic studies have revealed clonal hematopoiesis by HSCs with altered genes. PIGA, DNMT3A, ASXL1, BCOR, 6pLOH, and HLA class I allele mutations are common in patients with AA. The genomic landscape of AA is distinct from that of the myelodysplastic syndrome or age-related clonal hematopoiesis. This suggests that escape from an autoimmune attack is strongly associated with clonal hematopoiesis in AA. Eltrombopag (EPAG), a thrombopoietin receptor agonist, has recently emerged as a novel therapeutic agent for AA. Further studies are needed to clarify whether EPAG induces clonal expansion of these clones.

Congenital hemolytic anemias are classified into three major categories: red cell membrane disorders, hemoglobinopathies, and red cell enzyme disorders. The membrane disorders are caused by abnormalities in erythrocyte membrane proteins and are often associated with disease-specific deformations of red blood cells. Historically, membrane disorders have been classified according to morphology. In recent years, however, comprehensive genetic analysis with next-generation sequencing has been performed in patients with hemolytic anemia for whom making an accurate diagnosis is difficult. These studies have led to the identification of new causative genes, but there have been inconsistent associations in some cases between the diagnosed disease and the patient’s clinical manifestations. Thalassemia is a hemoglobinopathy caused by a quantitative abnormality of one or the other of the globin chains in hemoglobin. Most Japanese patients with thalassemia have mild forms of the disease, which is different from reports in other countries. However, with globalization, the proportion of Japanese patients with intermediate or severe anemia is increasing. Therefore, it is incumbent on hematologists in Japan to be knowledgeable regarding prenatal diagnosis of and gene therapy for thalassemia.

Among the hematologic tumors, lymphoid malignancies, especially B-cell lymphomas (BLs), are categorized according to the WHO classification into a large number of entities, which are aggregates of clinically and biologically diverse diseases. It is thought that various molecular genetic abnormalities are involved in lymphoid tumorigenesis. Recent advances in genetic analysis technology have resulted in the discovery of many novel and recurrent genetic abnormalities. In particular, those associated with diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL), and mantle cell lymphoma have been identified utilizing molecular pathology techniques, which is important aspect for the future development of novel therapeutic drugs and indications for clinical trials. In this section, the possibility of patient-stratification based on genetic abnormalities of DLBCL and FL, which are particularly prevalent among mature BLs, are described. I also introduce the genetic features and clinical importance of BL and MCL identified in a small number of patients in Japan.

Mature T- and NK-cell neoplasms are a heterogeneous hematological malignancy. The current treatment of mature T- and NK-cell lymphoma depends on combination chemotherapy with or without auto/allogeneic hematopoietic stem cell transplantation. Recent comprehensive, integrated genetic analyses have revealed distinct genetic and molecular subgroups, which are related to different therapeutic responses. Thus, the genetic landscape of mature T- and NK-cell neoplasms is essential for the development of novel treatment modalities and offers opportunities for individualized therapy. This review aims to discuss the recent progress regarding genetic and molecular analyses of mature T- and NK-cell neoplasms toward stratified therapy.

Hodgkin lymphoma is characterized by CD30 overexpression and downstream NF-κB pathway activation in Hodgkin/Reed-Sternberg (H/RS) cells. Accordingly, CD30 and its aberrant downstream signaling have been investigated as potential treatment targets for the disease. Given that H/RS cells are surrounded by a variety of immune cells that constitute a unique inflammatory and immunoinhibitory microenvironment, efforts have also been made to treat the disease by reversing the abnormal tumor immune milieu. In recent years, a CD30 antibody-drug conjugate and immune checkpoint inhibitors have been approved for the treatment of Hodgkin lymphoma and have demonstrated remarkable treatment efficacy. These new agents have not only contributed to improved survival of patients refractory to conventional chemotherapy but have also enabled further understanding on the molecular pathogenesis of Hodgkin lymphoma in relation to the key signaling of the PD-1 and JAK/STAT pathways.

Differentiation of hematopoietic stem/progenitor cells should be tightly regulated depending on the environmental changes to maintain homeostasis. For example, erythropoiesis repression and myelopoiesis induction are widely recognized as infectious/inflammatory conditions. Transcription factors are expected to play significant roles in achieving such alterations. However, the precise mechanism by which the differentiation trajectory shift is controlled under environmental changes has not fully been elucidated. In this study, we showed that Bach transcription factors organize the erythro-myeloid differentiation in hematopoietic stem/progenitor cells in response to the environmental changes. Under the steady state, Bach transcription factors support erythroid differentiation and repress myeloid differentiation by regulating the expression of their target genes. In contrast, the functions of Bach transcription factors were repressed, which induced myelopoiesis and repressed erythropoiesis, under emergency conditions, such as infection/inflammation. Competitive roles of Bach transcription factors and C/EBP, the key regulator of myelopoiesis, might be important for tuning erythro-myeloid differentiation trajectory and its shift in response to infection/inflammation. Disfunction of Bach transcription factors was considered to be related to anemia in chronic inflammation and myelodysplastic syndromes. In addition, considering previous findings, Bach2 might possess important roles in the conditioning of the hematopoietic system for subsequent emergency conditions.

Recent development of massive parallel-sequencing technology has revealed the genetic basis of pediatric T-cell acute lymphoblastic leukemia (T-ALL). However, epigenetic profiles of T-ALL, such as DNA methylation, have not been well characterized. To describe the epigenetic landscape of T-ALL, we investigated DNA methylation profiles of 79 cases with pediatric T-ALL by using the EPIC methylation array, which allowed us to perform more profound analyses, including the OpenSea region. Moreover, we conducted combined analyses of methylation data using our previous expression and mutation data. Based on DNA methylation profiles, pediatric T-ALL was clustered into four distinct subtypes, which exhibited remarkable association with genetic signatures and expression features, as well as profiles of normal T-cell development. Furthermore, our study revealed the importance of methylation status at binding sites of polycomb-repressive complex components and transcription factors, such as SPI1, in the classification of pediatric T-ALL based on DNA methylation status. These results might be helpful in the development of new therapeutic strategies for pediatric T-ALL.

Hematopoietic stem cells (HSCs) reside at the top of the differentiation hierarchy and differentiate into multiple hematopoietic cell lineages via a finely-tuned process. HSCs have been shown to locate in a specific microenvironment (niche) that integrates HSC function, including self-renewal, and differentiation. Accumulating evidence has revealed that various types of cells in and around the bone marrow participate in HSC function regulation as niche-comprising cells. Furthermore, recent studies have identified the stromal cells closely associated with bone marrow vasculatures as HSC niche components. The remarkable advances in experimental technologies have enabled the identification of functional differences among distinct niche cell types in the bone marrow. In this article, we review recent evidence regarding the HSC niche by focusing on the cell types associated with bone marrow vasculatures and discuss future research directions.

Regular prophylaxis using factor (F) VIII products to prevent bleeding in patients with hemophilia A (PWHAs) results in markedly suppressed onset of arthropathy and greatly contributes to improved quality of life. However, some issues remain with the use of clotting factor replacement therapy. The need for multiple intravenous infusions is associated with substantial mental and physical burden, and the inhibitor development results in difficulty of hemostatic management. To overcome these unmet needs, a recombinant humanized anti-FIXa/FX bispecific antibody mimicking FVIIIa function (emicizumab) was created. In phase 1/2 clinical studies, Japanese patients with PWHAs were treated with once-weekly subcutaneous administration of emicizumab. The annual bleeding rates were markedly reduced, irrespective of inhibitor use. A phase 3 global study for PWHA with inhibitor demonstrated a statistically significant efficacy, whereas thrombotic microangiopathy and thromboembolism were reported in 5 patients treated with emicizumab concomitantly with multiple infusions of activated prothrombin complex concentrates. In Japan, emicizumab (HEMLIBRA^®) was approved for treatment of PWHAs with inhibitor on March 2018. In conclusion, emicizumab has promising features. Its subcutaneous bioavailability and long half-life (T1/2; approximately 30 days) enable effective bleeding prophylactic treatment at inhibitor status. Additional studies are warranted to establish clinical data on its safety and to define suitable assays for hemostatic monitoring.

Although immune thrombocytopenia (ITP) and thrombotic thrombocytopenic purpura (TTP) appear similar, their symptoms differ. The number of domestic patients diagnosed with ITP and TTP annually has been estimated to be around 24,000 and 400, respectively. Moreover, no major differences in the incidence rate, age of onset, and prognosis have been observed between Europe, the United States (US), and Japan. Both ITP and acquired TTP are autoimmune diseases that require immunosuppressive therapy, though lethal TTP requires the use of plasma exchange in combination with immunosuppression. In Europe and the US, the monoclonal antibody rituximab has been widely used for ITP and TTP since approximately 10 years ago. However, no public health insurance indication has been available for rituximab in Japan. For this reason, investigator-initiated clinical trials were conducted. As a result, rituximab had subsequently been indicated for ITP in 2017. Meanwhile, TTP was designated as an intractable disease in Japan in 2015, and the first clinical practice guidelines were published in 2017. A single-arm study involving rituximab was conducted on high-risk patients in whom treatment with five plasma exchanges was ineffective or ADAMTS13 inhibitor was >2 BU/ml. Approval for the new indication of rituximab for acquired TTP is expected in 2019.