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Background: Persistent hemolytic anemia and a lack of oral treatments are challenges for patients with paroxysmal nocturnal hemoglobinuria who have received anti-C5 therapy or have not received complement inhibitors. Iptacopan, a first-in-class oral factor B inhibitor, has been shown to improve hemoglobin levels in these patients., Methods: In two phase 3 trials, we assessed iptacopan monotherapy over a 24-week period in patients with hemoglobin levels of less than 10 g per deciliter. In the first, anti-C5-treated patients were randomly assigned to switch to iptacopan or to continue anti-C5 therapy. In the second, single-group trial, patients who had not received complement inhibitors and who had lactate dehydrogenase (LDH) levels more than 1.5 times the upper limit of the normal range received iptacopan. The two primary end points in the first trial were an increase in the hemoglobin level of at least 2 g per deciliter from baseline and a hemoglobin level of at least 12 g per deciliter, each without red-cell transfusion; the primary end point for the second trial was an increase in hemoglobin level of at least 2 g per deciliter from baseline without red-cell transfusion., Results: In the first trial, 51 of the 60 patients who received iptacopan had an increase in the hemoglobin level of at least 2 g per deciliter from baseline, and 42 had a hemoglobin level of at least 12 g per deciliter, each without transfusion; none of the 35 anti-C5-treated patients attained the end-point levels. In the second trial, 31 of 33 patients had an increase in the hemoglobin level of at least 2 g per deciliter from baseline without red-cell transfusion. In the first trial, 59 of the 62 patients who received iptacopan and 14 of the 35 anti-C5-treated patients did not require or receive transfusion; in the second trial, no patients required or received transfusion. Treatment with iptacopan increased hemoglobin levels, reduced fatigue, reduced reticulocyte and bilirubin levels, and resulted in mean LDH levels that were less than 1.5 times the upper limit of the normal range. Headache was the most frequent adverse event with iptacopan., Conclusions: Iptacopan treatment improved hematologic and clinical outcomes in anti-C5-treated patients with persistent anemia - in whom iptacopan showed superiority to anti-C5 therapy - and in patients who had not received complement inhibitors. (Funded by Novartis; APPLY-PNH ClinicalTrials.gov number, NCT04558918; APPOINT-PNH ClinicalTrials.gov number, NCT04820530.)., (Copyright © 2024 Massachusetts Medical Society.)

Paroxysmal cold hemoglobinuria (PCH) is a rare autoimmune hemolytic anemia often overlooked as a potential etiology of hemolysis and is challenging to diagnose because of the complicated testing methods required. We performed a systematic review of all reported cases to better assess the clinical, immunohematologic, and therapeutic characteristics of PCH. We systematically analyzed PubMed, Medline, and EMBASE to identify all cases of PCH confirmed by Donath-Landsteiner (DL) testing. Three authors independently screened articles for inclusion, and systematically extracted epidemiologic, clinical, laboratory, treatment, and outcomes data. Discrepancies were adjudicated by a fourth author. We identified 230 cases, with median presentation hemoglobin of 6.5 g/dL and nadir of 5.5 g/dL. The most common direct antiglobulin test (DAT) result was the presence of complement and absence of immunoglobulin G (IgG) bound to red blood cells, although other findings were observed in one-third of cases. DL antibody class and specificity were reported for 71 patients, of which 83.1% were IgG anti-P. The use of corticosteroids is common, although we found no significant difference in the length of hospitalization for patients with and without steroid therapy. Recent reports have highlighted the use of complement inhibitors. Among patients with follow-up, 99% (213 of 216) were alive at the time of reporting. To our knowledge, this represents the largest compilation of PCH cases to date. We discovered that contemporary PCH most commonly occurs in children with a preceding viral infection, corticosteroid use is frequent (but potentially ineffective), and DAT results are more disparate than traditionally reported., (© 2023 by The American Society of Hematology. Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.)

Introduction: Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by uncontrolled activation of the terminal complement pathway, leading to intravascular hemolysis (IVH) and a prothrombotic state. Treatment with terminal complement (C5) inhibitors, the current standard of care, suppresses IVH and reduces the risk of thrombosis and the associated morbidity and mortality. Opportunities exist to further improve care by alternative modes of administration and the reduction of clinically significant anemia and transfusion dependence caused by extravascular hemolysis in some patients., Areas Covered: This review describes the pathophysiology of PNH, provides an overview of the current standard of care, and discusses potential avenues for enhancing patient care, with a focus on the literature describing new and emerging treatments that target the alternative pathway. Emerging treatments include biosimilars and novel C5 inhibitors as well as agents with novel mechanisms of action that target the proximal complement pathways (C3 inhibitors, factor B inhibitors, and factor D inhibitors)., Expert Opinion: Alternative complement pathway inhibitors may offer further benefit as long as terminal complement is completely inhibited to reduce IVH and disease activity. This may lead to improvements in adherence and health-related quality of life for patients with PNH.

Objectives: To study the association between paroxysmal nocturnal hemoglobinuria (PNH) clone and immunosuppressive therapy (IST) in children with severe aplastic anemia (SAA)., Methods: A retrospective analysis was performed on the medical data of 151 children with SAA who were admitted and received IST from January 2012 to May 2020. According to the status of PNH clone, these children were divided into a negative PNH clone group ( n =135) and a positive PNH clone group ( n =16). Propensity score matching was used to balance the confounding factors, and the impact of PNH clone on the therapeutic effect of IST was analyzed., Results: The children with positive PNH clone accounted for 10.6% (16/151), and the median granulocyte clone size was 1.8%. The children with positive PNH clone had an older age and a higher reticulocyte count at diagnosis ( P <0.05). After propensity score matching, there were no significant differences in baseline features between the negative PNH clone and positive PNH clone groups ( P >0.05). The positive PNH clone group had a significantly lower overall response rate than the negative PNH clone group at 6, 12, and 24 months after IST ( P <0.05). The evolution of PNH clone was heterogeneous after IST, and the children with PNH clone showed an increase in the 3-year cumulative incidence rate of aplastic anemia-PNH syndrome ( P <0.05)., Conclusions: SAA children with positive PNH clone at diagnosis tend to have poor response to IST and are more likely to develop aplastic anemia-PNH syndrome.

Paroxysmal Nocturnal Hemoglobinuria (PNH) is a disease as simple as it is complex. PNH patients develop somatic loss-of-function mutations in phosphatidylinositol N -acetylglucosaminyltransferase subunit A gene ( PIGA ), required for the biosynthesis of glycosylphosphatidylinositol (GPI) anchors. Ubiquitous in eukaryotes, GPI anchors are a group of conserved glycolipid molecules responsible for attaching nearly 150 distinct proteins to the surface of cell membranes. The loss of two GPI-anchored surface proteins, CD55 and CD59, from red blood cells causes unregulated complement activation and hemolysis in classical PNH disease. In PNH patients, PIGA -mutant, GPI (-) hematopoietic cells clonally expand to make up a large portion of patients' blood production, yet mechanisms leading to clonal expansion of GPI (-) cells remain enigmatic. Historical models of PNH in mice and the more recent PNH model in rhesus macaques showed that GPI (-) cells reconstitute near-normal hematopoiesis but have no intrinsic growth advantage and do not clonally expand over time. Landmark studies identified several potential mechanisms which can promote PNH clonal expansion. However, to what extent these contribute to PNH cell selection in patients continues to be a matter of active debate. Recent advancements in disease models and immunologic technologies, together with the growing understanding of autoimmune marrow failure, offer new opportunities to evaluate the mechanisms of clonal expansion in PNH. Here, we critically review published data on PNH cell biology and clonal expansion and highlight limitations and opportunities to further our understanding of the emergence of PNH clones., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Colden, Kumar, Munkhbileg and Babushok.)

Paroxysmal nocturnal haemoglobinuria (PNH) is characterized by complement-mediated intravascular haemolysis, severe thrombophilia and bone marrow failure. While for patients with bone marrow failure the treatment follows that of immune-mediated aplastic anaemia, that of classic, haemolytic PNH is based on anti-complement medication. The anti-C5 monoclonal antibody eculizumab has revolutionized treatment, resulting in control of intravascular haemolysis and thromboembolic risk, with improved long-term survival. Novel strategies of complement inhibition are emerging. New anti-C5 agents reproduce the safety and efficacy of eculizumab, with improved patient convenience. Proximal complement inhibitors have been developed to address C3-mediated extra-vascular haemolysis and seem to improve haematological response., (© 2021 The Authors. British Journal of Haematology published by British Society for Haematology and John Wiley & Sons Ltd.)

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired hematopoietic stem cell genetic mutation disease that causes defective erythrocyte membrane hemolysis. Its pathologic basis is the mutation of the PIG-A gene, whose product is necessary for the synthesis of glycosylphosphatidylinositol (GPI) anchors; the mutation of PIG-A gene results in the reduction or deletion of the GPI anchor, which leads to the deficiency of GPI-anchored proteins (GPI-APs), such as CD55 and CD59, which are complement inhibitors. The deficiency of complement inhibitors causes chronic complement-mediated intravascular hemolysis of GPI-anchor-deficient erythrocyte. PIG-A gene mutation could also be found in bone marrow hematopoietic stem cells (HSCs) of healthy people, but they have no growth advantage; only the HSCs with PIG-A gene mutation in PNH patients have this advantage and expand. Besides, HSCs from PIG-A -knockout mice do not show clonal expansion in bone marrow, so PIG-A mutation cannot explain the clonal advantage of the PNH clone and some additional factors are needed; thus, in recent years, many scholars have put forward the theories of the second hit, and immune escape theory is one of them. In this paper, we focus on how T lymphocytes are involved in immune escape hypothesis in the pathogenesis of PNH., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Li, Dong, Wang and Shao.)

The complement system is an important defense mechanism against pathogens; however, in certain pathologies, the system also attacks human cells, such as red blood cells (RBCs). In paroxysmal nocturnal hemoglobinuria (PNH), RBCs lack certain complement regulators which sensitize them to complement-mediated lysis, while in autoimmune hemolytic anemia (AIHA), antibodies against RBCs may initiate complement-mediated hemolysis. In recent years, complement inhibition has improved treatment prospects for these patients, with eculizumab now the standard of care for PNH patients. Current complement inhibitors are however not sufficient for all patients, and they come with high costs, patient burden, and increased infection risk. This review gives an overview of the underlying pathophysiology of complement-mediated hemolysis in PNH and AIHA, the role of therapeutic complement inhibition nowadays, and the high number of complement inhibitors currently under investigation, as for almost every complement protein, an inhibitor is being developed. The focus lies with novel therapeutics that inhibit complement activity specifically in the pathway that causes pathology or those that reduce costs or patient burden through novel administration routes., (© 2021. The Author(s).)

In this large single-centre study, we report high prevalence (25%) of, small (<10%) and very small (<1%), paroxysmal nocturnal hemoglobinuria (PNH) clones by high-sensitive cytometry among 3085 patients tested. Given PNH association with bone marrow failures, we analyzed 869 myelodysplastic syndromes (MDS) and 531 aplastic anemia (AA) within the cohort. PNH clones were more frequent and larger in AA vs. MDS (p = 0.04). PNH clone, irrespective of size, was a good predictor of response to immunosuppressive therapy (IST) and to stem cell transplant (HSCT) (in MDS: 84% if PNH+ vs. 44.7% if PNH-, p = 0.01 for IST, and 71% if PNH+ vs. 56.6% if PNH- for HSCT; in AA: 78 vs. 50% for IST, p < 0.0001, and 97 vs. 77%, p = 0.01 for HSCT). PNH positivity had a favorable impact on disease progression (0.6% vs. 4.9% IPSS-progression in MDS, p < 0.005; and 2.1 vs. 6.9% progression to MDS in AA, p = 0.01), leukemic evolution (6.8 vs. 12.7%, p = 0.01 in MDS), and overall survival [73% (95% CI 68-77) vs. 51% (48-54), p < 0.0001], with a relative HR for mortality of 2.37 (95% CI 1.8-3.1; p < 0.0001) in PNH negative cases, both in univariate and multivariable analysis. Our data suggest systematic PNH testing in AA/MDS, as it might allow better prediction/prognostication and consequent clinical/laboratory follow-up timing., (© 2021. The Author(s), under exclusive licence to Springer Nature Limited.)

The aim of this study is to collect paroxysmal nocturnal hemoglobinuria (PNH) patient data from hematology centers all over Turkey in order to identify clinical features and management of PNH patients. Patients with PNH were evaluated by a retrospective review of medical records from 19 different institutions around Turkey. Patient demographics, medical history, laboratory findings, and PNH-specific information, including symptoms at the diagnosis, complications, erythrocyte, and granulocyte clone size, treatment, and causes of death were recorded. Sixty patients (28 males, 32 females) were identified. The median age was 33 (range; 17-77) years. Forty-six patients were diagnosed as classic PNH and 14 as secondary PNH. Fatigue and abdominal pain were the most frequent presenting symptoms. After eculizumab became available in Turkey, most of the patients (n = 31/46, 67.4%) were switched to eculizumab. Three patients with classic PNH underwent stem cell transplantation. The median survival time was 42 (range; 7-183 months) months. This study is the first and most comprehensive review of PNH cases in Turkey. It provided us useful information to find out the differences between our patients and literature, which may help us understand the disease.

Background: FLAER-based flow cytometry assay is considered the gold standard for diagnosis of paroxysmal nocturnal hemoglobinuria (PNH). CD157 is a recently reported marker for GPI-anchored protein found both on neutrophils and monocytes. This study highlights the robustness of FLAER and CD157 combination to identify PNH clones in a high sensitivity assay. Though rare, the data shown highlight the presence of CD157 negativity in few cases re-emphasizing the importance of FLAER for PNH diagnosis., Methods: A single 5-color tube-FLAER Alexa488/ CD157PE/ CD15PECy5/ CD64PE-Cy7 & CD45APCH7-was used for a high sensitivity PNH assay., Results: Of 364 cases, 59(16.2%) cases had PNH clone in both granulocytes and monocytes. PNH clone sizes ranged from 0.02% to 96.6% in granulocytes and 0.07% to 96.3% in monocytes based on their FLAER-negative, CD157-negative phenotype. Twenty-two of the 59 PNH cases (37.3%) had WBC clone size of <1%. In addition, there were 10 cases which showed absence of CD 157 expression on both granulocytes and monocytes but on FLAER staining showed normal staining patterns. Three of these ten cases also showed a PNH clone based on absence of FLAER expression on both granulocytes and monocytes., Conclusion: FLAER and CD157 is a robust combination for diagnosis of clinical and subclinical PNH. Absence of CD157 expression in normal WBCs, though rare, should be kept in mind and re-emphasizes the importance of FLAER for the high sensitivity PNH assay., (© 2020 John Wiley & Sons Ltd.)

The absence of the cell-surface complement inhibitors CD55 and CD59 is considered the mechanism underlying the complement-mediated destruction of affected red blood cells (RBCs) in paroxysmal nocturnal hemoglobinuria (PNH) patients, but Factor H (FH), a fluid-phase complement inhibitor, has also been proposed to be involved. However, the status of FH on the PNH patient RBC surface is unclear and its precise role in PNH pathogenesis remains to be further defined. In this study, we identified significantly lower levels of surface-bound FH on the affected CD59 - RBCs than on the unaffected CD59 + RBCs. Although this reduction in surface-bound FH on PNH RBCs was accompanied by decreased surface sialic acid levels, the enzymatic removal of sialic acids from these RBCs did not significantly affect the levels of surface-bound FH. We further observed higher surface levels of FH on the C3b/iC3b/C3d high RBCs than on C3b/iC3b/C3d low RBCs within the affected PNH RBCs of patients treated with eculizumab. Finally, we determined that enhanced surface levels of FH on CD55/CD59-deficient RBCs from mice and PNH patients protected against complement-mediated hemolysis. Taken together, our results suggest that a reduced surface level of FH is another important mechanism underlying the pathogenesis of PNH.

Hepatitis-associated aplastic anemia is a well-recognized clinical syndrome in which marrow failure follows the development of hepatitis. Although aplastic anemia is intimately related to paroxysmal nocturnal hemoglobinuria, until now, no cases of PNH-associated hepatitis have been described. We report a case of recurrent acute hepatitis preceding the clinical onset of PNH. Treatment of PNH with the complement inhibitor eculizumab (Soliris ® ) prevented both recurrences of episodes of intravascular hemolysis and liver enzyme alteration. This is the first known published case of PNH-associated hepatitis.

In the UK, early work on paroxysmal nocturnal haemoglobinuria (PNH) was conducted by John Dacie who, at the Hammersmith Hospital, first hypothesised that the PNH abnormality might arise through a somatic mutation; and who outlined with S.M. Lewis the relationship between PNH and aplastic anaemia. When the phosphatidylinositol glycan anchor biosynthesis Class A (PIGA) gene was identified by Taroh Kinoshita's group, jointly with him the Hammersmith group proved that PNH is caused in most patients by a single somatic mutation in the PIGA gene. At the same time, after Bruno Rotoli had spent a sabbatical at the Hammersmith, the 'immune escape model' for the pathogenesis of PNH was developed. Early this century, Peter Hillmen, formerly at the Hammersmith and now in Leeds, spearheaded the use of the complement-blocking (anti-C5) antibody eculizumab. This new medicine radically changed the management and the clinical course of patients with PNH. Recently a derivative of eculizumab with more favourable pharmacokinetics has been introduced. In view of the fact that these agents are associated with C3-dependent extravascular haemolysis, it is important that a number of inhibitors of the proximal complement pathway are now in the offing and may further improve the life of patients with PNH., (© 2020 British Society for Haematology and John Wiley & Sons Ltd.)

The therapy algorithm for severe aplastic anaemia (sAA) is established but moderate AA (mAA), which likely reflects a more diverse pathogenic mechanism, often represents a treatment/management conundrum. A cohort of AA patients (n = 325) was queried for those with non-severe disease using stringent criteria including bone marrow hypocellularity and chronic persistence of moderately depressed blood counts. As a result, we have identified and analyzed pathological and clinical features in 85 mAA patients. Progression to sAA and direct clonal evolution (paroxysmal nocturnal haemoglobinuria/acute myeloid leukaemia; PNH/AML) occurred in 16%, 11% and 1% of mAA cases respectively. Of the mAA patients who received immunosuppressive therapy, 67% responded irrespective of time of initiation of therapy while conservatively managed patients showed no spontaneous remissions. Genomic analysis of mAA identified evidence of clonal haematopoiesis with both persisting and remitting patterns at low allelic frequencies; with more pronounced mutational burden in sAA. Most of the mAA patients have autoimmune pathogenesis similar to those with sAA, but mAA contains a mix of patients with diverse aetiologies. Although progression rates differed between mAA and sAA (P = 0·003), cumulative incidences of mortalities were only marginally different (P = 0·095). Our results provide guidance for diagnosis/management of mAA, a condition for which no current standard of care is established., (© 2020 The Authors. British Journal of Haematology published by British Society for Haematology and John Wiley & Sons Ltd.)

Introduction: The myeloproliferative neoplasms (MPN) are clonal diseases that confer an increased risk of thrombohemorrhagic complications. Paroxysmal nocturnal hemoglobinuria (PNH) is a rare clonal disease associated with an increased thrombotic risk. Small PNH clones are prevalent in aplastic anemia and myelodysplastic syndrome patients, but their prevalence in MPN patients is unknown., Patients and Methods: Consecutive patients with MPN followed up at a single center were recruited. PNH clones were analyzed in erythrocytes and white blood cells by flow cytometry., Results: PNH clones were detected in 2% of patients and were more common in JAK2 V617F positive patients. We could not detect any differences in clinical manifestations or complications in patients either with or without PNH clones because of the small patient numbers., Conclusion: The prevalence of PNH clones in MPN is similar to that described in myelodysplastic syndromes. Whether PNH clones influence MPN phenotype and complications should be studied prospectively in larger patient cohorts and over long-term follow-up., (Copyright © 2019 Elsevier Inc. All rights reserved.)

The terminology applied to autoimmune hemolytic anemia (AIHA) seems inconsistent. We aimed to evaluate the consistency of definitions used for diagnosis and treatment. In this systematic review of literature from January 2006 to December 2015, we assessed heterogeneity in the definition of AIHA and its subtypes, refractory disease, disease phase, severity, criteria for treatment response, and response durability. A Medline search for anemia, hemolytic, autoimmune was supplemented with keyword searches. Main exclusions were conference abstracts, animal and non-English studies, and studies with <10 cases. Of 1371 articles retrieved, 1209 were excluded based on titles and abstracts. Two authors independently reviewed 10% and 16% of abstracts and full papers, respectively. After full-paper review, 84 studies were included. AIHA was most frequently (32 [52%] of 61) defined as hemolytic anemia with positive direct antiglobulin test (DAT) and exclusion of alternatives, but 10 of 32 also recognized DAT-negative AIHA. A lower threshold for diagnosis of DAT-negative AIHA was observed in literature on chronic lymphocytic leukemia. Definitions of anemia, hemolysis, and exclusion criteria showed substantial variation. Definitions of primary/secondary cold agglutinin disease/syndrome were not consistent. Forty-three studies provided criteria for treatment response, and other than studies from 1 center, these were almost entirely unique. Other criteria were rarely defined. Only 7, 0, 3, 2, 2, and 3 studies offered definitions of warm AIHA, paroxysmal cold hemoglobinuria, mixed AIHA, AIHA severity, disease phase, and refractory AIHA, respectively. Marked heterogeneity in the time period sampled indicates the need to standardize AIHA terminology., (© 2019 by The American Society of Hematology.)

The plasticity of induced pluripotent stem cells (iPSCs) with the potential to differentiate into virtually any type of cells and the feasibility of generating hematopoietic stem progenitor cells (HSPCs) from patient-derived iPSCs (iPSC-HSPCs) has many potential applications in hematology. For example, iPSC-HSPCs are being used for leukemogenesis studies and their application in various cell replacement therapies is being evaluated. The use of iPSC-HSPCs can now provide an invaluable resource for the study of diseases associated with the destruction of HSPCs, such as bone marrow failure syndromes (BMFSs). Recent studies have shown that generating iPSC-HSPCs from patients with acquired aplastic anemia and other BMFSs is not only feasible, but is also a powerful tool for understanding the pathogenesis of these disorders. In this article, we highlight recent advances in the application of iPSCs for disease modeling of BMFSs and discuss the discoveries of these studies that provide new insights in the pathophysiology of these conditions., (Copyright © 2019. Published by Elsevier Inc.)

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare hematologic disease characterized by intravascular hemolysis, thrombophilia, and marrow failure. Its phenotype is due to absent or reduced expression of GPI-linked complement regulators and subsequent sensitivity of hematopoietic cells to complement-mediated damage and lysis. Introduction of the terminal complement inhibitor eculizumab drastically improved outcomes in PNH patients; however, despite this improvement, there remain several challenges faced by PNH patients and physicians who care for them. One of the most important is increasing awareness of the heterogeneity with which patients can present, which can lead to significant delays in recognition. Data from the Canadian PNH Registry are presented to demonstrate the variety of presenting symptoms. In Canada, geography precludes consolidation of care to just a few centers, so management is distributed across academic hospitals, linked together as the Canadian PNH Network. The Network over the last several years has developed educational programs and clinical checklists and has worked to standardize access to diagnostics across the country. Herein, we address some of the common diagnostic and therapeutic challenges faced by PNH physicians and give our recommendations. Gaps in knowledge are also addressed, and where appropriate, consensus opinion is provided., (© 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Atypical hemolytic uremic syndrome (aHUS), C3 glomerulopathy (C3G), and paroxysmal nocturnal hemoglobinuria (PNH) are prototypical disorders of complement dysregulation. Although complement overactivation is common to all, cell surface alternative pathway dysregulation (aHUS), fluid phase alternative pathway dysregulation (C3G), or terminal pathway dysregulation (PNH) predominates resulting in the very different phenotypes seen in these diseases. The mechanism underlying the dysregulation also varies with predominant acquired autoimmune (C3G), somatic mutations (PNH), or inherited germline mutations (aHUS) predisposing to disease. Eculizumab has revolutionized the treatment of PNH and aHUS although has been less successful in C3G. With the next generation of complement therapeutic in late stage development, these archetypal complement diseases will provide the initial targets.

In fibrous dysplasia/McCune-Albright syndrome (FD/MAS), bone and bone marrow are, to varying degrees, replaced by fibro-osseous tissue typically devoid of hematopoietic marrow. Despite the extensive marrow replacement in severely affected patients, bone marrow failure is not commonly associated with FD/MAS. We present a 14-year-old girl with FD/MAS, who developed pancytopenia and extramedullary hematopoiesis (EMH) with no identified cause, in the setting of iatrogenic thyrotoxicosis and hyperparathyroidism. Pancytopenia, requiring monthly blood transfusions, persisted despite multiple strategies to correct these endocrinopathies. Due to worsening painful splenomegaly, likely as a result of sequestration, splenectomy was performed. Following splenectomy, pancytopenia resolved and patient has since been transfusion-independent. We report the first detailed case of bone marrow failure and EMH in FD/MAS. The etiology of marrow failure is likely multifactorial and related to the loss of marrow reserve due to extensive polyostotic FD, exacerbated by iatrogenic thyrotoxicosis and hyperparathyroidism. Mini Abstract: A patient with fibrous dysplasia developed bone marrow failure and extramedullary hematopoiesis. The etiology likely involved loss of hematopoetic marrow space and uncontrolled endocrinopathies. Splenectomy was therapeutic.

Paroxysmal nocturnal hemoglobinuria is a rare acquired hematologic disorder, the most serious complication of which is thrombosis. The increased incidence of thrombosis in paroxysmal nocturnal hemoglobinuria is still poorly understood, but unlike many other thrombotic disorders, predominantly involves complement-mediated mechanisms. This review article discusses the different factors that contribute to the increased risk of thrombosis in paroxysmal nocturnal hemoglobinuria. Paroxysmal nocturnal hemoglobinuria leads to a complex and multifaceted prothrombotic state due to the pathological effects of platelet activation, intravascular hemolysis and neutrophil/monocyte activation. Platelet and endothelial microparticles as well as oxidative stress may play a role. Impaired fibrinolysis has also been observed and may be caused by several mechanisms involving interactions between complement activation, coagulation and fibrinolysis. While many factors may affect thrombosis in paroxysmal nocturnal hemoglobinuria, the relative contribution of each mechanism that has been implicated is difficult to quantify. Further studies, including novel in vivo and in vitro thrombosis models, are required in order to define the role of the individual mechanisms contributing to thrombosis, impaired fibrinolysis and clarify other complement-driven prothrombotic mechanisms in paroxysmal nocturnal hemoglobinuria., (Copyright© 2018 Ferrata Storti Foundation.)

The clinical significance of paroxysmal nocturnal haemoglobinuria (PNH) in children with aplastic anaemia (AA) remains unclear. We retrospectively studied 57 children with AA between 1992 and 2010. During the follow-up, five patients developed clinical PNH, in whom somatic PIGA mutations were detected by targeted sequencing. The 10-year probability of clinical PNH development was 10·2% (95% confidence interval, 3·6-20·7%). Furthermore, the detection of minor PNH clones by flow cytometry at AA diagnosis was a risk factor for the subsequent development of clinical PNH. These patients with PNH clones at AA diagnosis should undergo periodic monitoring for potential clinical PNH development., (© 2017 John Wiley & Sons Ltd.)

Dyskeratosis congenita (DC) is a bone marrow failure syndrome associated with telomere dysfunction. The progression and molecular determinants of hematopoietic failure in DC remain poorly understood. Here, we use the directed differentiation of human embryonic stem cells harboring clinically relevant mutations in telomerase to understand the consequences of DC-associated mutations on the primitive and definitive hematopoietic programs. Interestingly, telomere shortening does not broadly impair hematopoiesis, as primitive hematopoiesis is not impaired in DC cells. In contrast, while phenotypic definitive hemogenic endothelium is specified, the endothelial-to-hematopoietic transition is impaired in cells with shortened telomeres. This failure is caused by DNA damage accrual and is mediated by p53 stabilization. These observations indicate that detrimental effects of telomere shortening in the hematopoietic system are specific to the definitive hematopoietic lineages. This work illustrates how telomere dysfunction impairs hematopoietic development and creates a robust platform for therapeutic discovery for treatment of DC patients., (Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.)

Paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome are diseases of excess activation of the alternative pathway of complement that are treated with eculizumab, a humanized monoclonal antibody against the terminal complement component C5. Eculizumab must be administered intravenously, and moreover some patients with paroxysmal nocturnal hemoglobinuria on eculizumab have symptomatic extravascular hemolysis, indicating an unmet need for additional therapeutic approaches. We report the activity of two novel small-molecule inhibitors of the alternative pathway component Factor D using in vitro correlates of both paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome. Both compounds bind human Factor D with high affinity and effectively inhibit its proteolytic activity against purified Factor B in complex with C3b. When tested using the traditional Ham test with cells from paroxysmal nocturnal hemoglobinuria patients, the Factor D inhibitors significantly reduced complement-mediated hemolysis at concentrations as low as 0.01 μM. Additionally the compound ACH-4471 significantly decreased C3 fragment deposition on paroxysmal nocturnal hemoglobinuria erythrocytes, indicating a reduced potential relative to eculizumab for extravascular hemolysis. Using the recently described modified Ham test with serum from patients with atypical hemolytic uremic syndrome, the compounds reduced the alternative pathway-mediated killing of PIGA -null reagent cells, thus establishing their potential utility for this disease of alternative pathway of complement dysregulation and validating the modified Ham test as a system for pre-clinical drug development for atypical hemolytic uremic syndrome. Finally, ACH-4471 blocked alternative pathway activity when administered orally to cynomolgus monkeys. In conclusion, the small-molecule Factor D inhibitors show potential as oral therapeutics for human diseases driven by the alternative pathway of complement, including paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome., (Copyright© Ferrata Storti Foundation.)

Rationale: Radium-223-Dichloride (Ra-223) is an alpha-emitter, used to treat bone metastases. Patients with high metastatic burden and/or with increased trabecular bone uptake could present a higher incidence of hematologic toxicity. We hypothesized that these two factors are predictors of bone marrow failure., Material and Methods: A computer algorithm discriminated between trabecular bone ( B Vol ) and tumor metastases ( M Vol ) within pretherapeutic whole-body skeletal SPECT/CT ( N = 47). The program calculated the metastatic invasion percent (INV%) as the M Vol /( M Vol + B Vol ) ratio and extracted the B Vol mean counts. B Vol counts were correlated to % drop of hemoglobin (Hb), leukocytes (WBC), and platelets (PLT) after 3/6 Ra-223 cycles. Patient-specific and computational-derived parameters were tested as predictors of hematologic toxicity with MANOVA., Results: B Vol counts correlated with drop of Hb ( R = 0,65, p < 0.01) and PLT ( R = 0,45, p < 0.01). Appendicular B Vol counts showed a better correlation ( p < 0.05, p < 0.01, and p < 0.001 for Hb, WBC, and PLT, resp.). INV% directly correlated with B Vol counts ( R = 0.68, p < 0.001). At MANOVA, grade III/IV toxicity was predicted by INV% ( p < 0.01), by long-bone invasion ( p < 0.005), and by B Vol counts ( p < 0.05)., Conclusions: In patients with significant bone tumor burden, degree of bone invasion and trabecular bone uptake are predictors of subsequent bone marrow failure.

Autoimmune hemolytic anemia (AIHA) in childhood, including paroxysmal cold hemoglobinuria, is an uncommon, potentially life-threatening disorder. AIHA is a recognized complication of several varieties of lymphoproliferative disorders, including high-grade B-cell lymphoma, but it has not been associated with Burkitt lymphoma in people without an underlying immunodeficiency. When AIHA occurs in association with lymphoproliferative disorders, it may precede or accompany the diagnosis of malignant disease or herald relapse. We report a novel case of a previously healthy child diagnosed with paroxysmal cold hemoglobinuria 14 months preceding the development of Burkitt lymphoma.

Remarkable advances have been made over past decades in understanding the pathogenesis of complement-mediated diseases. This has led to development of new therapies for, and in some cases re-classification of, complement-driven diseases. This success is due to not only insight from human patients but also studies using transgenic animal models. Animal models that mimic human diseases are useful tools to understand the mechanism of disease and develop new therapies but there are also limitations due to species differences in their complement systems. This review provides a summary of transgenic animal models for three human diseases that are at the forefront of anti-complement therapy, paroxysmal nocturnal hemoglobinuria (PNH), atypical hemolytic uremic syndrome (aHUS) and C3 glomerulopathy (C3G). They are discussed here as examples to highlight the values and limitations of animal modeling in complement-driven diseases., (Copyright © 2016. Published by Elsevier GmbH.)

Peliosis hepatis (PH) is a condition involving benign tumors pathologically characterized by multiple blood-filled cavities, mostly affecting the liver and spleen. Androgenic-steroids are widely used in patients with bone marrow failure syndromes (e.g.: aplastic anemia) and these patients are at increased risk of developing PH. Although patients with PH are generally asymptomatic, PH can progress to liver failure and even fatal spontaneous intraabdominal hemorrhage. Therefore, early diagnosis is critical in order to prevent life-threatening complications of PH. We herein report a patient with PH which had been treated with danazol, who presented with liver dysfunction and multiple hepatic lesions on imaging studies at the time of diagnosis. Although the patient presented with disseminated intravascular coagulation (DIC), a bone marrow biopsy revealed no evidence of leukemic transformation. The patient was diagnosed as having danazol-induced PH, and these abnormalities spontaneously resolved after the discontinuation of danazol. PH is one of the most important complications of long-term administration of androgenic-steroids. Although the mechanisms remain unclear, the multiple blood-filled cavities characteristic of PH may be responsible for the development of DIC. Therefore, monitoring of coagulation markers might also be a key strategy for early diagnosis of PH.

Weekly monitoring of absolute neutrophil count (ANC) under deferiprone therapy in thalassemia patients is recommended to avoid agranulocytosis adverse event. Actually, this recommendation may not be applicable in clinical setting. Our study aimed to establish incidence of neutropenia under deferiprone (DFP) monotherapy when it was monitored bimonthly due to socioeconomic conditions effecting local and refugee thalassemic patients including Syrian origin (SYR; n = 26) and Turkish origin (TR; n = 26) groups. Patients on DFP were followed up for 12 months. Fifteen neutropenic episodes were seen in 5 patients. All 5 patients (4 from SYR group and 1 from TR group) had splenomegaly and hypersplenism, and neutropenia ceased in 4 patients after splenectomy despite continuation of deferiprone. In the TR group, the frequency of patients who have neutropenia (absolute neutrophil count [ANC] <1500/mm(3)) was 3.8% (n = 1) in the 1st month, no patients in TR group had neutropenia until 10th month when again there was 1 patient with mild neutropenia. In SYR group, the frequency of patients who have neutropenia was 3.8% (n = 1), 7.7% (n = 2), and 11.5% (n = 3) in the 1st, 2nd, and 3rd months, respectively, and was found to be 3.8% (n = 1) between 6 and 12 months. Whether or not DFP therapy should be interrupted in case of mild neutropenia and the frequency of monitoring ANC in real-life conditions should be documented with further studies. Other causes of neutropenia in DFP-treated patients should also be kept in mind.

The inherited bone marrow failure syndromes (IBMFS) are rare disorders in which there is usually some form of bone marrow failure and typical changes in physical appearance, associated with a family history of the same disorder. Patients with IBMFS have a very high risk of developing myelodysplastic syndrome, acute myeloid leukemia, and solid tumors. The latest technology applied to the molecular pathogenesis of these disorders has led to identification of specific genetic mutations and now facilitates determining the appropriate diagnosis and management of afflicted patients. In this section, we describe physical and laboratory findings and management of the major IBMFS: Fanconi anemia, dyskeratosis congenita, Shwachman-Diamond syndrome, and Diamond Blackfan anemia. We also discuss their possible implications in the clinical features of Japanese patients.

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired disorder of the hematopoietic stem cell that makes blood cells more sensitive to the action of complement. Patients experience intravascular hemolysis, smooth muscle dystonia, renal failure, arterial and pulmonary hypertension, recurrent infectious diseases and an increased risk of notably dreadful thrombotic complications. The diagnosis is made by flow cytometry. Efforts have been recently performed to improve the sensitivity and the standardization of this technique. PNH is frequently associated with aplastic anemia or low-risk myelodysplasia and may be asymptomatic. Management of the classical form of PNH has been dramatically revolutionized by the development of eculizumab, which brings benefits in terms of hemolysis, quality of life, renal function, thrombotic risk, and life expectancy. Prophylaxis and treatment of arterial and venous thrombosis currently remain a challenge in PNH., (© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Paroxysmal nocturnal haemoglobinuria (PNH) is a rare haematological disease characterised by chronic haemolysis, pancytopenia and venous thrombosis. The condition is attributable to a lack of control of complement attack on erythrocytes, thrombocytes and leukocytes, and can be diagnosed by means of flow cytometry. In this quality assurance study, we have reviewed information from the medical records of all patients tested for PNH using flow cytometry at our laboratory over a ten-year period., Material and Method: In the period 2000-2010 a total of 28 patients were tested for PNH using flow cytometry at the Department of Immunology and Transfusion Medicine, Oslo University Hospital. We have reviewed the results of these examinations retrospectively together with information from medical records and transfusion data for the patients concerned., Results: Flow cytometry identified 22 patients with PNH: four with classic disease and 18 with PNH secondary to another bone marrow disease. Five patients had atypical thrombosis. Seventeen patients received antithymocyte globulin or drug treatment; of these, six recovered from their bone marrow disease, while six died and five had a need for long-term transfusion. Five patients with life-threatening bone marrow disease underwent allogeneic stem cell transplantation, three of whom died. Six of 22 patients received eculizumab; the need for transfusion has been reduced or eliminated in three patients treated with eculizumab over a longer period., Interpretation: Flow cytometry identified PNH in a majority of patients from whom we obtained samples. Most patients had a PNH clone secondary to bone marrow failure. Atypical thrombosis should be borne in mind as an indication for the test. Treatment with eculizumab is relevant for selected patients with PNH.

The understanding of the clinical manifestations in paroxysmal nocturnal haemoglobinuria (PNH) has made great progress. The main symptoms of this disease such as abdominal pain, renal failure or pulmonary hypertension and even the basis of the dramatic thrombophilia can be related to intravascular haemolysis and liberation of free haemoglobin resulting in NO depletion. In addition, there has been a recent great progress in elucidating the pathophysiology of clonal expansion within PNH bone marrow. In the majority of patients with haemolytic PNH, there are additional mutations within genes beyond PIG-A and rather affecting growth and differentiation of clonal bone marrow cells. In contrast to the formerly proposed single mechanism hypotheses such as immune selection or intrinsic gain of clonal dominance, this appears to follow a pattern of a complex clonal hierarchy putatively integrating both earlier anticipated mechanisms. Treatment of PNH is mainly supportive. The only curative approach as allogeneic stem cell transplantation should only be applied to patients with complications such as secondary bone marrow aplasia or transformation into MDS or AML. Symptomatic haemolytic PNH will be treated with eculizumab, an inhibitor of the terminal complement cascade. Treatment with eculizumab can significantly prevent PNH-related symptoms including the abnormal thrombophilia. Recently, it was demonstrated that in contrast to untreated historic PNH patients, meanwhile a normal life expectancy is observed in eculizumab-treated patients. The recently approved vaccine against meningococci type B by the European Medical Agency (EMA) could probably further help to prevent meningococcal sepsis due to the induced complement deficiency by eculizumab., (© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)