TAFRO syndrome is characterized by thrombocytopenia with unknown etiology. The assessment of immature platelet fraction (IPF) is useful for differential diagnoses that include thrombocytopenia. However, the significance of IPF in cases of TAFRO syndrome remains to be reported. We present a case of TAFRO syndrome wherein the patient demonstrated a marked increase in IPF without thrombocytopenia, which offers vital information concerning TAFRO diagnosis and the serial measurements of IPF during treatment. A 65-year-old man presenting with fever was admitted to our hospital. He exhibited mild splenomegaly and lymphadenopathy, as well as rapidly worsening renal failure and fluid retention. These indications prompted the initiation of corticosteroid therapy. A normal platelet count and aberrantly high IPF implied abnormal thrombopoiesis, and subsequent bone-marrow findings suggested TAFRO syndrome. The platelet counts started to decrease following the corticosteroid therapy, but the treatment refractoriness prompted the urgent administration of rituximab. Thereafter, the platelet count nadir remained for approximately one month, whereas the decreasing IPF trend preceded platelet recovery. In the present case, a high pre-treatment IPF was demonstrated before the emergence of thrombocytopenia, and a decreasing trend of IPF was observed before platelet recovery during treatment. Therefore, serial IPF measurements could be useful for the early diagnosis and prognostication of TAFRO syndrome.

A 26-year-old man presented with fever, multiple lymphadenopathies, polyclonal hypergammaglobulinemia, and an elevated serum interleukin-6 (IL-6) level. Multicentric Castleman disease (MCD) was diagnosed by lymph node biopsy. Treatment with prednisolone (PSL) was initiated; however, its efficacy was limited. During PSL tapering, rapidly progressive anemia and thrombocytopenia developed concurrently with increased reticulocyte level, elevated serum LDH level, decreased haptoglobin level, and positive direct Coombs test. Based on these findings, Evans syndrome, which is a concurrent development of autoimmune hemolytic anemia and immune thrombocytopenia, was confirmed. The PSL dose was increased but was ineffective. Therefore, treatment with tocilizumab was initiated, and the clinical findings of both MCD and Evans syndrome improved. The clinical course of this case suggests that tocilizumab could be a treatment option for Evans syndrome complicated with MCD. Three other cases of Evans syndrome complicated with MCD have also been reported; however, this is the first case that shows the efficacy of tocilizumab as treatment for both MCD and Evans syndrome.

A 56-year-old woman was diagnosed with classical Hodgkin lymphoma in December 2012. She achieved complete remission (CR) with six cycles of adriamycin, bleomycin, vinblastine, and dacarbazine (ABVD). In March 2015, she experienced a relapse marked by high fever, respiratory discomfort, and pain in the left thigh owing to tumor involvement of the femur. She was treated with one cycle of brentuximab vedotin (BV), followed by irradiation of the left femoral lesion. She achieved partial remission (PR) but developed recurrence after the third cycle of BV. She achieved PR again with two cycles of standard bleomycin, etoposide, doxorubicin, cyclophosphamide, vincristine, procarbazine, and prednisone (BEACOPP) regimen; therefore, autologous stem cell transplantation (ASCT) was performed. Because the dosing interval used for BV therapy was longer than that in the recommended schedule, we could not definitively attribute her recurrence to BV resistance. Moreover, she maintained a good performance status after recurrence during subsequent cycles of BV therapy. Because of attaining PR after ASCT, she subsequently received a total of 12 BV cycles for consolidation. She achieved CR 3 months after ASCT and has remained in CR until 29 months. For patients who show relapse after initial BV therapy, retreatment with BV should be carefully considered. Patients who show relapse after achieving at least PR with initial BV therapy are potential candidates for post-ASCT BV maintenance therapy to reduce their tumor burden.

Acquired factor V (FV) inhibitor is a rare disorder. Herein we report a case of an 82-year-old Japanese woman with FV inhibitor exhibiting a pseudo decline in the activities of the multiple coagulation factors. After rectal cancer surgery, she received antibiotic therapy for wound infection. As prothrombin and activated partial thromboplastin time was prolonged, heparin for atrial fibrillation was discontinued without improvement. Coagulation factor activity assays revealed deficiencies in II, V, VII, VIII, IX, X, XI, and XII factor activities; in particular, the FV activity was markedly decreased to <1%. The cross-mixing test findings revealed an inhibitor pattern, and multiple coagulation factor inhibitors were positive. The FV inhibitor level was high at 62 Bethesda U/ml. The patient exhibited no bleeding tendency with the prolonged wound infection without immunosuppressive therapy. The inhibitor disappeared four months after the onset.

A 76-year-old man presented with a tracheal tumor associated with severe respiratory obstruction. A tracheotomy was performed due to respiratory failure. F-fluorodeoxyglucose (FDG) -positron emission tomography/computed tomography revealed an abnormal accumulation of FDG (maximum standardized uptake value: 16) in the trachea. A histopathological examination of the tracheal biopsy revealed extranodal NK/T-cell lymphoma, nasal type (ENKL). He was treated with concurrent radiotherapy (50 Gy) for the tracheal tumor and three courses of two-thirds dose ofdexamethasone, etoposide, ifosfamide, and carboplatin. Although the tumor responded remarkably well to this therapy, the patient died of an ENKL recurrence in the lungs and liver 11 months post therapy.

HLA 1-locus-mismatched unrelated donors (1MMUD) are used in allogeneic hematopoietic stem cell transplantation (allo-HCT) for patients who lack an HLA-matched donor. Here we retrospectively reviewed 3,313 patients with acute leukemia or myelodysplastic syndrome who underwent bone marrow transplantation from an HLA allele-matched unrelated donor (MUD) or 1MMUD in 2009-2014. We compared the outcomes of MUD (n＝2,089) and 1MMUD with antithymocyte globulin [ATG; 1MM-ATG (＋) ; n＝109] with those of 1MMUD without ATG [1MM-ATG (−) ; n＝1,115]. In the 1MM-ATG (＋) group, the median total dose of ATG (thymoglobulin) was 2.5 (range, 1.0-11.0) mg/kg. The rates of grade III-IV acute GvHD, non-relapse mortality (NRM), and overall mortality were significantly lower in the MUD group than in the 1MM-ATG (−) group [hazard ratio (HR) 0.77; P＝0.016; HR, 0.74, P<0.001; and HR, 0.87, P＝0.020, respectively]. Similarly, the rates of grade III-IV acute GvHD, NRM, and overall mortality were significantly lower in the 1MM-ATG (＋) group than in the 1MM-ATG (−) group (HR, 0.42, P＝0.035; HR, 0.35, P<0.001; and HR, 0.71, P＝0.042, respectively). Even in the recent cohort, the outcome of allo-HCT from 1MM-ATG (−) was inferior to that of allo-HCT from MUD. Nevertheless, the negative impact of 1MMUD disappeared with the use of low-dose ATG without exacerbating the risk of relapse.

Reportedly, patients with cancer have an increased risk (four- to seven-fold) of developing thrombotic events (TEs) compared with healthy volunteers. Multiple myeloma (MM) is one of the neoplasms that exhibit a high incidence of TEs, and approximately 10% patients with MM develop TEs during their clinical courses. The underlying risk factors of TEs are classified into patient-, disease-, and treatment-related factors. Specific treatment-related risk factors comprise the use of immunomodulatory drugs combined with dexamethasone. As the occurrence of TE in patients hampers the treatment for MM itself, which results in unfavorable outcomes, elucidating TE pathogenesis and adequate prophylaxis for each patient are essential to prevent MM-related TEs.

Among all types of myeloproliferative neoplasms (MPNs), polycythemia vera (PV) and essential thrombocythemia (ET) require careful management of both thrombosis and hemostasis. One recent concern associated with MPNs is the JAK2 mutation (V617F). This mutation is essential for MPN pathology, but it has also garnered attention for its association with thrombosis. Several studies have reported the mechanisms underlying the onset of thrombosis in both PV and ET and have also discussed the association between JAK2 mutations and thrombotic tendencies. Arterial thrombosis is a common clinical symptom that is associated with the diagnosis and course of both PV and ET. Particularly, cerebral infarction has been identified as the leading cause of death in patients with untreated PV. Notably, PV and ET are also associated with a high incidence of venous thromboembolism (VTE). The occurrence of this type of thrombosis at atypical sites, such as cerebral venous sinus thrombosis and splanchnic vein thrombosis (SVT), is not uncommon. Generally, patients with PV and ET have good life expectancy; their treatment essentially focuses on dealing with thrombosis and bleeding. Phlebotomy may be used for treating patients with PV; however, low-dose aspirin is used to prevent the onset of arterial thrombosis. For patients with a history of VTE, oral anticoagulants are commonly prescribed to prevent recurrence.

Paroxysmal nocturnal hemoglobinuria (PNH) arises as a consequence of clonal expansion of hematopoietic stem cells that have acquired a somatic mutation in the PIGA gene. The resulting hematopoietic cells have deficiencies in the GPI-anchored complement regulatory proteins CD55 and CD59, which account for the intravascular hemolysis that is the primary clinical manifestation of PNH. Thromboembolism is a major cause of morbidity and mortality in PNH, particularly in Caucasian patients. In a previous report on the clinical course of PNH patients in the United States and Japan, we showed that thrombosis was significantly more prevalent in white PNH patients than in Asian PNH patients. The pathophysiological mechanisms underlying thrombosis in PNH have not been fully clarified, and multiple factors are likely to be involved. Eculizumab, a humanized monoclonal antibody, targets the terminal complement protein C5 and inhibits terminal complement-mediated hemolysis associated with PNH. Brodsky et al. reported that eculizumab treatment reduces the risk of clinical thromboembolism in patients with PNH. These facts strongly suggest that the main cause of thrombosis in PNH is complement activation and/or hemolysis. In this review, the pathophysiology of thrombosis in PNH is discussed in the context of observations in PNH patients treated with eculizumab.

Multiple myeloma (MM) cells acquire dormancy and drug resistance via their interaction with bone marrow stroma cells (BMSCs) in a hypoxic microenvironment. In this study, we found a positive expression of CD180/MD-1 complex (a non-canonical toll-like receptor) on MM cells, which was markedly up-regulated under adherent and/or hypoxic conditions. Bacterial lipopolysaccharide (LPS) enhanced the growth of MM cells via the activation of MAP kinases, an effect which showed a positive correlation with the expression levels of CD180. LPS administration significantly increased CD180/CD138 double-positive cell number in a murine xenograft model after the inoculation of MM cells directly attached to BMSCs. Notably, the shRNA-mediated knockdown of CD180 terminated the LPS response in vitro and in vivo. Promoter analyses identified IKZF1 (Ikaros) as a pivotal transcriptional activator of the CD180 gene, whose transcription was activated via cell adhesion and hypoxia by increasing Ikaros expression and its binding to the promoter region. Pharmacological targeting of Ikaros with lenalidomide ameliorated the response of MM cells to LPS in a CD180-dependent manner in vitro and in vivo. CD180/MD-1 pathway may represent a novel mechanism for the regulation of the growth of MM cells in BM milieu and may serve as a therapeutic target to prevent the regrowth of dormant MM cells.

A chimeric antigen receptor (CAR) comprises an extracellular ligand recognition domain linked to CD3ζ and induces T-cell activation upon antigen binding. Recently, the potential of CD19-targeted CAR T-cells (CAR-T) to treat multiple myeloma has been explored. A group in the University of Pennsylvania reported that 4 out of 10 patients with refractory myeloma achieved an objective response (sCR: 1, VGPR: 1, and PR: 2). Although the resultant cancer ablation was an arresting sight, it remains unclear whether CD19 is a suitable target for myeloma. Therefore, CAR-T therapy employing alternative target antigens is being attempted. Some current clinical trials are utilizing CAR against differentiation antigens, including CD138, CD38, and kappa light chain. B-cell maturation antigen (BCMA) is also a potential candidate. A group in the NCI described 12 patients with refractory myeloma enrolled in a BCMA-CAR phase 1 clinical trial. Two patients receiving the highest dosage attained an objective response. Nevertheless, considerable research is required for CAR immunotherapy to become universally available to patients with myeloma. The current enthusiasm for the development of this cutting-edge technology is justified because extraordinary evidence indicates that it is effective, although this may not apply to every case. CAR-T therapy for myeloma is currently undergoing rapid, wide-scale growth both in academia and in industry-sponsored clinical development.

The 2016 revised WHO classification of tumors of hematopoietic and lymphoid tissues has incorporated novel molecular markers, such as calreticulin (CALR) mutations, for the diagnosis of myeloproliferative neoplasms (MPNs). Typically, CALR mutations are detected in 25%-30% of patients with essential thrombocythemia (ET) or primary myelofibrosis (PMF) and can lead to frameshifts that produce proteins with a novel C-terminal. In addition, the CALR mutation plays a crucial role in the MPN pathogenesis. The second major revision comprises the change in RBC parameters for polycythemia diagnosis; additionally, it emphasizes BM biopsy for the diagnosis of PV. Previously, PV was often underdiagnosed when considering the Hb levels of >18.5 g/dl for males and >16.5 g/dl for females; thus, the 2016 revision lowered these levels to >16.5 g/dl for males and >16.0 g/l for females. The third major revision is the introduction of a novel entity “prefibrotic/early” PMF (prePMF) to PMF. Although megakaryocytic proliferation and atypia were observed in in BM biopsy specimens of prePMF, these were not accompanied by reticulin fibrosis > grade 1. Thus, the inferior prognosis of prePMF was reported in comparison with “true” ET.

Unique frameshift mutations in the calreticulin (CALR) gene, which encodes a molecular chaperone present in the endoplasmic reticulum, were identified in a subset of patients with myeloproliferative neoplasms (MPNs). Recently, it has been reported that mutant CALR constitutively activates the thrombopoietin (TPO) receptor MPL, even in the absence of TPO, thereby inducing cellular transformation. Hence, the tumorigenic role of mutant CALR in the development of MPNs is now clear; nevertheless, the precise molecular mechanism the interaction between mutant CALR and MPL remains elusive. We recently illustrated that the accumulation of mutant CALR in the Golgi apparatus and its N-glycan binding capacity are needed for its tumorigenic capacity, including the interaction and activation of MPL. These findings implied that mutant CALR recognizes MPL during the receptor maturation using its original property as a molecular chaperone. Although the molecular mechanism underlying the activation of MPL by CALR remains elusive, it became clear that the mechanism of interaction between mutant CALR and MPL is quite different from that of TPO, the natural ligand, and MPL.

During the past decade, substantial advances have been made in our understanding of the genetic basis of myelodysplastic syndromes (MDS), wherein a spectrum of major mutational targets associated with MDS, such as splicing factors and epigenetic regulators, has been revealed. The impact of mutations in these genes on disease subtypes and prognosis has also been evaluated. A mutation in SF3B1, one of the spliceosome machinery components, defines a distinct MDS subtype characterized by ring sideroblasts, indolent clinical course, and favorable clinical outcome. On the other hand, mutation in TP53 is observed in 5-10% of cases and is associated with an aggressive phenotype, higher frequency of copy number abnormalities, and poor prognosis. Even in the setting of hematopoietic stem-cell transplantation, patients with TP53 mutations, particularly in cases where complex cytogenetic abnormalities were also present, showed extremely poor prognosis. Because the importance of molecular profiles in the prognosis of MDS is being better understood, treatment decisions may begin incorporating this information in addition to conventional clinical factors.

Graft-versus-host disease (GVHD) caused by patient and donor human leukocyte antigen (HLA) mismatch is a complication of unrelated hematopoietic stem cell transplantation (UR-HSCT) that leads to reduced success rates. To date, studies on HLA alleles in transplant have provided important information on unrelated donor selection. In this study on the effects of specific HLA alleles on acute GVHD in UR-HSCT, HLA-C^＊14:02 was found to be significantly associated with an increased risk of acute GVHD. Patient HLA-C^＊14:02 and donor HLA-C^＊15:02 mismatch was usually KIR2DL-ligand mismatch in the GVH direction in Japanese UR-HSCT cohort, and the higher risk of severe acute GVHD for KIR2DL-ligand mismatch in GVH direction demonstrated in previous Japanese UR-HSCT study was attributable to this particular mismatch combination. Recently, the risk of acute GVHD after UR-HSCT was reported to be associated with the HLA-DP expression level, which is associated with the variant rs9277534 located in the 3′untranslated region (UTR) of the HLA-DPB1 gene. We constructed phylogenetic trees of HLA-DPB1 alleles using next-generation sequencing (NGS) HLA typing data that included introns and 3′UTRs. Results reported that rs9277534 represented a highly conserved region from exon 3 to the 3′UTR, which may lead to acute GVHD via a mechanism different from that observed using T-cell epitope mismatching algorithms, perhaps reflecting exon 2 polymorphisms. The usage of innovative technologies such as NGS in genetic analysis and HLA typing thus has profound implications in this field.

Post allogeneic hematopoietic stem cell transplantation, CD4^＋CD25^＋Foxp3^＋ regulatory T cells (Tregs) play a central role in the maintenance of self-tolerance and immune homeostasis. In recent years, various immune-modulating agents, including cyclophosphamide, mogamulizumab, and antibodies to inhibitory co-stimulating molecules (CTLA-4 and PD-1), have been used to control donor-derived immunity or host-tumor burden during the peritransplant period; however, the underlying impact of these agents on Treg homeostasis is yet to be characterized. In particular, recent retrospective analyses suggested that blockade (an inhibitory molecule) before and after HSCT was associated with abnormal Treg homeostasis and the development of severe acute GVHD and other immune-mediated complications. Our recent studies, using murine model and clinical sample analyses, aim to define the effects of immune-modulating agents on the reconstitution of each lymphocyte subset, particularly in terms of Treg homeostasis. An enhanced understanding of the reconstituting mechanisms and the target-specificity of post-HSCT GVL response combined with novel immunotherapy will enable the development of a safe and efficient therapeutic strategy.

Graft-versus-host disease (GVHD) -free, relapse-free survival (GRFS) is an important, composite endpoint for clinical trials, which provides a patient-centered measure of transplant success. This review discusses the results of the Japanese Transplant Registry study. This large-scale study examined 23,302 patients with hematological malignancy and characterized GRFS according to a variety of graft sources. The GRFS rate at 1 year was 41% in all patients. GRFS was superior in patients undergoing bone marrow transplantation compared to peripheral blood stem cell transplantation, owing to lower risk of developing grades III-IV acute and chronic GVHD. The best GRFS rates were observed in patients that received HLA-matched related bone marrow transplants; however, this was not the case in HLA-mismatched donors. GRFS after single-cord blood transplantation was almost comparable with HLA-matched unrelated bone marrow transplantation, possibly due to the low risk of chronic GVHD. Other factors associated with increased GRFS rates included female patients; use of anti-thymocyte globulin prophylaxis for standard-risk disease; recent transplantations; gender combinations other than from a female donor to a male patient; absence of prior autologous transplantation; myeloablative conditioning; negative cytomegalovirus serostatus; and use of tacrolimus-based GVHD prophylaxis. These results provide valuable information for deciding the best choice of graft sources and type of GVHD prophylaxis to be used.