This review is a commentary on an article entitled “Genetic variants in C5 and poor response to eculizumab” (N Engl J Med. 2014; 370: 632-639). The molecular basis for the poor response to eculizumab in Japanese patients is unclear. Of 345 Japanese patients with paroxysmal nocturnal hemoglobinuria (PNH) who received eculizumab, 11 showed a poor response. All 11 had a single missense C5 heterozygous mutation, c.2654 G>A, which predicts the polymorphism p.Arg885His. The prevalence of this mutation among patients with PNH (3.2%) was similar to that in healthy Japanese persons (3.5%). This polymorphism was also identified in a Han Chinese population. Non-mutant and mutant C5 both caused hemolysis in vitro, but only non-mutant C5 bound to and was blocked by eculizumab. In vitro hemolysis due to non-mutant and mutant C5 was completely blocked by N19-8, a monoclonal antibody that binds to a different site on C5 than does eculizumab. The functional capacity of the C5 polymorphism p.Arg885His, together with its failure to undergo blockade by eculizumab, accounts for the poor response to this agent in patients who carry this mutation.

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Myelodysplastic syndrome (MDS) is a clonal hematopoietic stem cell disease characterized by impaired hematopoiesis and an increased risk of transformation to acute myeloid leukemia. Various epigenetic regulators are mutated in MDS patients, indicating that accumulation of epigenetic alterations together with genetic alterations plays a crucial role in the development of MDS.

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Heme is a prosthetic group of hemoproteins playing important roles in oxygen transport, detoxification, circadian rhythm, microRNA processing, regulation of transcription, and translation. The majority of heme (-85%) is synthesized in red blood cells mainly for hemoglobin production, whereas hepatocytes account for most of the rest, functioning primarily in the synthesis of cytochrome P450 enzymes and mitochondrial respiratory enzymes. Thus, failure of heme biosynthesis causes severe inherited or acquired disorders in humans, including porphyria and sideroblastic anemia. The heme biosynthetic pathway is composed of eight enzymes that work in either mitochondria or the cytoplasm, which have been extensively researched and frequently reviewed. On the other hand, the mechanisms governing transport and intracellular trafficking of heme intermediates, as well as their potential links to human diseases, are poorly understood. Herein, we focus on recent understanding of the heme biosynthetic pathway and on human disorders due to defective heme synthesis in erythroid cells, such as X-linked sideroblastic anemia and erythropoietic protoporphyria.

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Genetic abnormalities including specific point mutations have recently been confirmed by applying comprehensive genome sequencing analyses. Molecular targeting therapies, which focus on the mutated proteins and over-expressed proteins in acute myeloid leukemia (AML) cells, are now being developed in clinical studies and/or based on in vitro analyses. This manuscript summarizes the genetic abnormalities in AML cells and some of the current molecular targeting therapies including FLT3 inhibitors (e.g. AC220; Quizartinib), Polo like kinase 1 (PLK1) inhibitors (e.g. BI-6727; Volasertib), IDH2 inhibitors (e.g. AG-221), and XPO1 inhibitors (e.g. KPT-330; Selinexor).

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Tyrosine kinase inhibitors (TKIs) have dramatically improved the clinical outcomes of patients with chronic myeloid leukemia (CML) in the chronic phase. However, even if these patients achieve and maintain marked molecular responses such as a complete molecular response (BCR-ABL/ABL≤0.032% by international scale), discontinuation of TKI treatment results in early molecular relapse in most cases. Although several factors such as the Sokal score and the duration of TKI treatment have been identified as being related to treatment-free remission (TFR), identification of more definite factors or clinical conditions that would enable us to select patients who can maintain TFR is required. Relapse after TKI discontinuation is considered to be attributable to CML stem cells surviving even in patients who maintain marked molecular responses. A number of in vitro experiments have shown that TKI by itself cannot kill CML stem cells. Also, CML stem cells are resistant to TKI in a manner dependent on self-renewal factors (Hh, Wnt/β-catenin), cell cycle regulators (PML), metabotropic factors (FOXO3, Alox5), and adhesion molecules (CXCR4). In addition, surface markers specific for CML stem cells such as IL-1RAP and CD26 have been identified. New therapeutic strategies targeting these molecules in combination with TKI hold promise of achieving a more effective strategy for curing CML.

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Activation of the JAK-STAT pathway by driver mutations of JAK2, CALR or MPL is the pathogenesis of myeloproliferative neoplasms (MPN). Mutations in epigenetic regulators that often coexist with driver mutations reinforce the function of MPN initiating cells and support MPN onset and maintenance. In myelofibrosis patients, JAK2 inhibitors exerted an innovative therapeutic effect on splenomegaly and constitutional symptoms, but had minimal effects on the JAK2V617F allele burden. Epigenetic abnormalities may be a good target for novel therapeutic strategies aiming to induce molecular remission in myelofibrosis patients. New information obtained by next-generation sequencing technologies would greatly contribute to elucidation of the mechanisms underlying MPN onset, progression and leukemic transformation.

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Acquired coagulation factor inhibitors are an autoimmune disease causing bleeding symptoms due to decreases in the corresponding factor (s) which result from the appearance of autoantibodies against coagulation factors (inhibitor). This disease is quite different from congenital coagulation factor deficiencies based on genetic abnormalities. In recent years, cases with this disease have been increasing, and most have anti-factor VIII autoantibodies. The breakdown of the immune control mechanism is speculated to cause this disease since it is common in the elderly, but the pathology and pathogenesis are presently unclear. We herein describe the pathology and pathogenesis of factor VIII and factor V inhibitors. Characterization of these inhibitors leads to further analysis of the coagulation process and the activation mechanisms of clotting factors. In the future, with the development of new clotting examination method (s), we anticipate that further novel findings will be obtained in this field through inhibitor analysis. In addition, detailed elucidation of the coagulation inhibitory mechanism possibly leading to hemostatic treatment strategies for acquired coagulation factor disorders will be developed.

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As the development of a hypercoagulable state in the setting of disseminated intravascular coagulation (DIC) induces localized infection, therapy for DIC should be evaluated according to the findings of examinations for both severe sepsis and DIC. DIC is classified into the following types: “bleeding type,” “organ failure type,” “asymptomatic type,” and “complication type.” The “bleeding type” and “organ failure type” are considered to reflect the “plasmin inhibitor (PI) deficiency type” and “antithrombin (AT) deficiency type,” respectively. In order to improve the diagnosis of DIC, in particular limitations in global coagulation tests, the Japanese Society of Thrombosis and Hemostasis recently proposed tentative diagnostic criteria for DIC using hemostatic molecular markers and AT. The recommendations for treatment of DIC, especially the use of AT concentrates, recombinant activated protein C and thrombomodulin, vary among several guidelines for the management of DIC. These agents inhibit the effects of key proteases in activating coagulation and consequently exert an anti-inflammatory effect on DIC. Hence, it is necessary to extensively evaluate these agents in well-conducted clinical trials.

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Immune thrombocytopenia (ITP) is an autoimmune disorder characterized by isolated thrombocytopenia caused by immune-mediated platelet destruction and impairment of platelet production. Recent studies have uncovered details involving the target regions of platelet-associated anti-GPIIb/IIIa antibodies, pathological differences depending on the specificity of target antigens, and cellular abnormalities, especially impairment of regulatory T cells contributing to the pathogenesis of ITP. Treatment of ITP has been changed dramatically by the application of thrombopoietin receptor agonists, TPO-RAs, in patients unresponsive to traditional steroids and splenectomy. Rituximab has also been used in Western countries for ITP patients and its long-term efficacy has become increasingly clear. Clinical problems awaiting solution in ITP management include improving the efficacy of treatments for newly-diagnosed ITP, confirmation of the long-term efficacy and safety of TPO-RAs, and determination of the positioning of rituximab in the treatment sequence of ITP.

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Atypical hemolytic uremic syndrome (aHUS) is a rare disease characterized by the triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure. The term aHUS was historically used to distinguish this disorder from Shiga-toxin producing Escherichia coli (STEC)-HUS. Many aHUS cases (approximately 70%) are reportedly caused by uncontrolled complement activation due to genetic mutations in the alternative pathway, including complement factor H (CFH), complement factor I (CFI), membrane cofactor protein (MCP), thrombomodulin (THBD), complement component C3 (C3), and complement factor B (CFB). Mutations in the coagulation pathway, such as diacylglycerol kinase ε (DGKE) and plasminogen, are also reported to be causes of aHUS. In this review, we have focused on aHUS due to complement dysfunction. aHUS is suspected based on plasma ADAMTS13 activity of 10% or more, and being negative for STEC-HUS, in addition to the aforementioned triad. Complement genetic studies provide a more specific diagnosis of aHUS. Plasma therapy is the first-line treatment for patients with aHUS and should be initiated as soon as the diagnosis is suspected. Recently, eculizumab, a humanized monoclonal antibody against C5, was shown to be an effective treatment for aHUS. Therefore, early diagnosis and identification of the underlying pathogenic mechanism is important for improving the outcome of aHUS.

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Iron is an essential metal for all living organisms. For example, iron is used in hemoglobin synthesis. However, iron overload can cause serious organ damage. Therefore, iron balance is tightly regulated while iron dynamically moves throughout the body, including the gastrointestinal tract, bone marrow, blood, liver, and spleen. Iron balance occasionally collapses, allowing either iron deficiency or iron overload to occur. Various laboratory tests and serum markers are now available for evaluating such iron dysregulation. The hepatic iron concentration, as determined by liver biopsy, and serum ferritin are both quite informative. In addition, certain novel markers and modalities are becoming available due to remarkable progress made in recent research on iron metabolism. In this review, the iron regulatory peptide-hormone hepcidin and non-transferrin-bound iron (NTBI) are introduced as novel potential biomarkers for iron metabolism.

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A 77-year-old man was diagnosed with cold agglutinin disease in 2004. He had been treated with prednisolone with stabilization of hemoglobin in the 6- to 8-g/dl range. However, his hemolytic anemia worsened, and computed tomography showed systemic lymphadenopathy in May 2012. A pathological diagnosis of small lymphocytic lymphoma was made based on an inguinal lymph node biopsy. Treatment was started with rituximab. However, there was no response to 6 doses of rituximab monotherapy. He next received 6 courses of bendamustine in combination with rituximab. This resulted in stabilization of hemoglobin and independence from transfusion support. To the best of our knowledge, this is only the second case report describing bendamustine plus rituximab treatment for non-Hodgkin lymphoma complicated by cold agglutinin disease. Our results in this case suggest bendamustine to potentially be a useful therapeutic option in patients with cold agglutinin disease.

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Adult T cell lymphoma-leukemia (ATL) is a highly aggressive disease and allogeneic hematopoietic transplantation (allo-HSCT) is the only therapeutic option for achieving a cure. However, some ATL patients cannot undergo HSCT. One of the important reasons for restricting HSCT in ATL is the high incidence of pulmonary complications associated with ATL including opportunistic infections, infiltration of ATL cells, and HTLV-1 associated bronchopneumonopathy. Herein, we report an ATL case with pulmonary infiltration of ATL cells successfully treated with allo-HSCT after improvement of pulmonary function with administration of the anti-CCR4 antibody mogamulizumab. To our knowledge, this is the first ATL case showing improvement of pulmonary invasion of ATL cells after treatment with mogamulizumab. In addition, this case suggests that mogamulizumab treatment might be useful as a bridge to allo-HSCT in ATL patients.

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A 51-year-old man with chronic myeloid leukemia (CML) was treated with imatinib (IM). After 24 months of treatment, he achieved a complete molecular response (CMR), which he sustained for 3 years. However, 4 months after discontinuing IM treatment, the CML relapsed. The patient was treated again with IM and achieved CMR. A combination of IM and interferon-α (IFNα) was administered for the following year, and then discontinued. The patient has since sustained CMR without therapy for 24 months, to date. This patient was found to have a BCL2L11 (BIM) deletion polymorphism. CML patients with a BIM deletion polymorphism show a low response to IM, and we infer that the BIM deletion polymorphism is a negative factor for discontinuation of IM. IFNα treatment is expected to prevent relapse during immunological surveillance. Therefore, the combination of IM and IFNα might be a feasible approach for CML patients who experience difficulty with IM discontinuation.

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A 71-year-old man with rheumatoid arthritis was referred to our hospital with complaints of face and leg edema and was admitted for management of acute renal failure. Type III cryoglobulinemia was diagnosed based on histopathological findings of a kidney biopsy which revealed cryoglobulinemic nephropathy. Immunofixation showed no serum M-proteins. Steroid pulse and apheresis were initiated but the proteinuria did not improve. Rituximab was administered four times weekly as a second-line treatment, eliminating the proteinuria, after which the steroid dose was gradually tapered until discontinuation. No recurrence of proteinuria was observed more than 1 year after termination of rituximab therapy. This suggests that rituximab exerts a long-term effect. Although this patient developed candidiasis during rituximab therapy, the therapy could be continued as the antifungal agents prevented exacerbation of the infection. Rituximab can be used for the treatment of steroid-refractory cryoglobulinemia. However, clinicians should remain aware of posssible infections associated with immunosuppression.

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