Natural history of paroxysmal nocturnal hemoglobinuria

Diagnosis and management of PNH: Review and recommendations from a Belgian expert panel

Despite its considerable morbidity and mortality, paroxysmal nocturnal haemoglobinuria (PNH) is still underdiagnosed. Patients with PNH can suffer from cardiovascular, gastrointestinal, neurological or haematological symptoms and refer to several specialists. The aim of this paper is to review the diagnosis and the management of PNH patients, with the primary focus on identifying high-risk groups. Additionally, the implementation and prognostic value of the defined high-risk groups will be commented on and the management of PNH patients is discussed from a Belgian perspective. Finally, based on the available data, recommendations are provided. Eculizumab is a potent C5 complement inhibitor and reduces intravascular haemolysis and thrombosis in PNH patients and improves their quality of life. As thrombosis is the main cause of death in PNH patients, identifying high-risk PNH patients in need of therapy is essential. Currently, novel complement inhibitors are in development and the first data seem promising. Another challenge in PNH is to identify new markers to assess the thrombotic risk to achieve a better risk-based prophylactic anti-thrombotic management. Finally, because of the low prevalence of the disease, PNH patients should be included in the prospective PNH registry, which will offer new insights on the natural course of the disease and the impact of treatment of PNH.

Iron Deficiency in Patients with Paroxysmal Nocturnal Hemoglobinuria: A Cross-Sectional Survey from a Single Institution in China

Background

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal hematopoietic disorder that often manifests with chronic intravascular hemolysis. Iron deficiency in patients with PNH is most often due to urinary losses of iron secondary to chronic intravascular hemolysis.

Material/Methods

This cross-sectional survey assessed the prevalence of iron deficiency in a Chinese population of PNH patients who were enrolled between May 2012 and October 2014.

Results

A total of 742 PNH cases were selected by FLARE and classified as classical PNH (15.36%), PNH in the setting of another specified bone marrow disorder (12.26%), and subclinical PNH (72.38%). The median age of all the patients was 32 years (range 5–77 years). The overall prevalence of iron deficiency was 17.9% among all the PNH patients enrolled in the survey, 76.3% (87/144) among those with classical PNH, 33.0% (30/91) among those with PNH in the setting of another specified bone marrow disorder, and 3.0% (16/537) among the subclinical PNH patients. The incidence of iron deficiency among classical PNH patients was higher than that in the other 2 subcategories (P-value=0.000). Multivariate analyses showed that age and disease duration were independent risk factors for iron deficiency in classical patients.

Conclusions

This survey shows that PNH patients were prone to iron deficiency, especially patients with classical PNH.

The Role of Whole-Body Magnetic Resonance Imaging (WB-MRI) in Patients with Paroxysmal Nocturnal Hemoglobinuria (PNH)

In PNH thromboembolic events (TEs) represent the leading cause of morbidity and mortality. Between Dec 2013 and Jan 2016 37 PNH patients (pts) (23 PNH, 14 AA/PNH; 51% (19/37) females; median age 44 years, median D-dimer levels 0.22 mg/l) were examined with a whole-body magnetic resonance imaging (WB-MRI) scan at 1.5 T to detect TEs. Pts were treated according to German PNH guidelines, including eculizumab therapy. 64% (24/37) of the pts had no documented TEs prior to observation. Two pts had suspected TEs in their clinical history. 29% of the pts (11/37) had a known history of venous thromboses (deep venous thrombosis (DVT) (5/11), portal venous thrombosis (PVT) (4/11), vena caval thrombosis (VCT) (2/11). A myocardial infarction was reported in one pt, and two had a cerebral venous sinus thrombosis (CVST) or a thalamic infarction. Six pts (16%) had at least two prior TEs. In pts with prior TEs no progression of the existing TEs was observed. In pts on eculizumab and prior TEs as well as treatment-naïve pts silent bone and renal infarctions were detected. Furthermore, a clinically non-critical arterial occlusion was identified. WB-MRI scans present a novel, non-invasive method to assess the complete vascular status of PNH pts and allow the detection of previously undiagnosed vascular complications, affecting treatment indications and regimens.

Spontaneous Remission in Paroxysmal Nocturnal Hemoglobinuria-Return to Health or Transition Into Malignancy?

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired syndrome characterized by intravascular hemolysis, thrombosis, and bone marrow failure. The disease is caused by a mutation in the PIG-A gene that leads to the lack of glycosylphosphatidylinositol-anchored complement regulatory molecules CD55 and CD59 on affected blood cell surfaces. In previous studies, spontaneous clinical remissions have been described. The disease manifestations are very heterogeneous, and we wanted to examine if true remissions and disappearance of the clone occur. In a follow-up of a nation-wide cohort of 106 Finnish patients with a PNH clone, we found six cases, where the clone disappeared or was clearly diminished. Two of the patients subsequently developed leukemia, while the other four are healthy and in clinical remission. According to our data, spontaneous remissions are not as frequent as described earlier. Since the disappearance of the PNH cell clone may indicate either a favorable or a poor outcome—remission or malignancy—careful clinical monitoring in PNH is mandatory. Nevertheless, true remissions occur, and further studies are needed to understand the immunological background of this phenomenon and to obtain a better understanding of the natural history of the disease.

Toward complement inhibition 2.0: Next generation anticomplement agents for paroxysmal nocturnal hemoglobinuria

Therapeutic complement inhibition by eculizumab has revolutionized the treatment of paroxysmal nocturnal hemoglobinuria (PNH) with a major impact on its natural history. Nevertheless, emerging unmet clinical needs may benefit from the development of novel complement inhibitors. Novel strategies of complement inhibition exploit different agents targeting C5, as well as compound intercepting the complement cascade at the level of its key component C3, or even upstream at the level of components involved in complement alternative pathway initiation. Many of these agents are already in their clinical development; preliminary data together with a deep understanding of PNH biology may help to anticipate their possible clinical effect. Novel anti-C5 agents include monoclonal antibodies (even long-lasting) as well as other small molecules bioavailable by subcutaneous administration; an anti-C5 small interfering RNA has been developed too. All these anti-C5 agents seem to recapitulate safety and efficacy of current eculizumab treatment; their main improvement pertains to better patient's convenience due to longer dosing interval and/or possible subcutaneous self-administration. The possibility of achieving a deeper C5 inhibition has been shown as well, but its actual clinical meaning remains to be elucidated. Upstream complement inhibitors include the anti-C3 small peptide compstatin (and its derivatives), and small inhibitors of complement factor D or complement factor B. This class of compounds anticipates a possible efficacy in prevention of C3-mediated extravascular hemolysis, in addition to inhibition of intravascular hemolysis, eventually leading to improved hematological responses. The availability of all these compounds will result soon in a substantial improvement of PNH management.

Expanding Complement Therapeutics for the Treatment of Paroxysmal Nocturnal Hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is widely regarded as an archetypal complement-mediated disorder that has propelled complement drug discovery in recent decades. Its pathology is driven by chronic complement dysregulation resulting from the lack of the glycosyl phosphatidyl inositol-linked regulators DAF and CD59 on susceptible erythrocytes. This complement imbalance fuels persistent C3 activation on affected erythrocytes, which culminates in chronic complement-mediated intravascular hemolysis. The clinical application of eculizumab, a humanized anti-C5 antibody that blocks terminal pathway activation, has led to drastic improvement of therapeutic outcomes but has also unveiled hitherto elusive pathogenic mechanisms that are now known to contribute to the clinical burden of a significant proportion of patients with PNH. These emerging clinical needs have sparked a true resurgence of complement therapeutics that offer the promise of even more effective, disease-tailored therapies for PNH. Here, we review the current state of complement therapeutics with a focus on the clinical development of C3-targeted and alternative pathway-directed drug candidates for the treatment of PNH. We also discuss the relative advantages and benefits offered by each complement-targeting approach, including translational considerations that might leverage a more comprehensive clinical intervention for PNH.

Evolutionary dynamics of paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal blood disorder characterized by hemolysis and a high risk of thrombosis, that is due to a deficiency in several cell surface proteins that prevent complement activation. Its origin has been traced to a somatic mutation in the PIG-A gene within hematopoietic stem cells (HSC). However, to date the question of how this mutant clone expands in size to contribute significantly to hematopoiesis remains under debate. One hypothesis posits the existence of a selective advantage of PIG-A mutated cells due to an immune mediated attack on normal HSC, but the evidence supporting this hypothesis is inconclusive. An alternative (and simpler) explanation attributes clonal expansion to neutral drift, in which case selection neither favours nor inhibits expansion of PIG-A mutated HSC. Here we examine the implications of the neutral drift model by numerically evolving a Markov chain for the probabilities of all possible outcomes, and investigate the possible occurrence and evolution, within this framework, of multiple independently arising clones within the HSC pool. Predictions of the model agree well with the known incidence of the disease and average age at diagnosis. Notwithstanding the slight difference in clonal expansion rates between our results and those reported in the literature, our model results lead to a relative stability of clone size when averaging multiple cases, in accord with what has been observed in human trials. The probability of a patient harbouring a second clone in the HSC pool was found to be extremely low (~10-8). Thus our results suggest that in clinical cases of PNH where two independent clones of mutant cells are observed, only one of those is likely to have originated in the HSC pool.

The mechanisms leading to expansion of HSC with mutations in the PIG-A gene that leads to the PNH phenotype remains unclear. Data so far suggests there is no intrinsic fitness advantage of the mutant cells compared to normal cells. Assuming neutral drift within the HSC compartment, we determined from first principles the incidence of the disease in a population, the average clone size in patients, the probability of clonal extinction, the likelihood of several separate clones coexisting in the HSC pool, and the expected expansion rate of a mutant clone. Our results are similar to what is observed in clinical practice. We also find that in such a model the probability of multiple PNH clones arising independently in the HSC pool is exceptionally small. This suggests that in clinical cases where more than one distinct clone is observed, all but one of the clones are likely to have emerged in cells that are downstream of the HSC population. We propose that PNH is perhaps the first disease where neutral drift alone may be responsible for clonal expansion leading to a clinical problem.

Prothrombotic mechanisms in patients with congenital p.Cys89Tyr mutation in CD59

BACKGROUND

Thrombosis is the prognostic factor with the greatest effect on survival in patients with paroxysmal nocturnal hemoglobinuria (PNH), who lack dozens of membrane surface proteins. We recently described a primary homozygous Cys89Tyr congenital nonfunctioning CD59 in humans with clinical manifestation in infancy, associated with chronic hemolysis, recurrent strokes, and relapsing peripheral demyelinating neuropathy. Here we investigated hypercoagulability mechanisms characterizing the syndrome.

METHODS

Membrane attack complex (MAC) deposition (anti-SC5b-9) and free hemoglobin (colorimetric assay) were assessed. Platelet activation was identified (anti-CD61, anti-CD62P), and microparticles (MPs) of 0.5-0.9 μm, were characterized (Annexin V, anti-human GlyA, anti-CD15, anti-CD14, anti-CD61). Platelet-monocyte aggregation was assessed with FlowSight.

FINDINGS

2/7 patients (29%) with homozygosity for Cys89Tyr and 6/12 (50%) with any of four described CD59 mutations had recurrent strokes. In plasma samples from four patients carrying identical mutations, MAC deposition was increased on RBCs (p < 0.0003), neutrophils (p < 0.009), and platelets (p < 0.0003). Free-plasma hemoglobin levels were abnormally high, up to 100 mg/dl. Patients with CD59 mutation had RBC-derived MP levels 9-fold higher than those in healthy controls (p < 0.01), and 2-2.5 fold higher than PNH patients (p < 0.09). Leukocyte-activated platelet aggregation was increased (p < 0.0062). Loss of CD59 was shown in the endothelium of these patients.

INTERPRETATION

Nonfunctioning CD59 is a major risk factor for stroke and hypercoagulability. Uncontrolled hemolysis causes massive MP release and endothelial heme damage. MAC attack on unprotected endothelium and platelet activation and aggregation with leukocytes mediate additional mechanisms leading to vascular occlusion. It is suggested that CD59 loss represents a major arterial prothrombotic factor in PNH and additional diseases.

High sensitivity 8-color flow cytometry assay for paroxysmal nocturnal hemoglobinuria granulocyte and monocyte detections

Flow cytometry is the gold standard in diagnosis of paroxysmal nocturnal hemoglobinuria (PNH) by detecting the absence of glycol-phosphatidyl inositol (GPI)-linked protein expression on granulocyte and monocyte surfaces. However, the current assays are not optimized and require improvement, particularly in reducing background fluorescence and optimizing sensitivity and specificity. With more fluorochromes available and with advances in instrument engineering, rare populations may be identified with high sensitivity. The present study assessed an 8-color combination of comprehensive GPI-linked markers, namely fluorescein-labeled proaerolysin (FLAER), cluster of differentiation 157 (CD157), CD24 and CD14, and the lineage markers for granulocyte (CD15) and monocyte (CD64) cells to detect PNH clones. Additionally, to optimize the PNH flow assay, a 'dump' channel was used, comprised of CD5 and CD19, to exclude non-specific binding in order to reduce background. This method aimed to improve sensitivity and reduce the background to create an optimized PNH flow cocktail. The results demonstrated that the current 4-color PNH combination identifies a CD55^- and FLAER⁺ population that is not PNH clones. By contrast, the 8-color panel delineated PNH clones from both monocyte and granulocytes by using granulocyte antigen (CD15) and monocyte antigen (CD64) as a gating strategy. The sensitivity was 0.01% for granulocytes and 0.05% for monocytes with an acquisition of 100,000 monocyte and granulocyte events. The background on a normal whole blood sample was 0.00076% on monocytes and 0.00277% on granulocytes. Thus, overall, the 8-color PNH assay exhibited high levels of specificity and sensitivity. The 8-color combination facilitated the improvement and enhancement of sensitivity in PNH clone identification, and may provide a useful tool for pathologists in PNH diagnosis and for monitoring patients at risk of developing classical/hemolytic PNH, to enable treatment to be delivered promptly.

Beyond the Role of CD55 as a Complement Component

The complement is a part of the immune system that plays several roles in removing pathogens. Despite the importance of the complement system, the exact role of each component has been overlooked because the complement system was thought to be a nonspecific humoral immune mechanism that worked against pathogens. Decay-accelerating factor (DAF or CD55) is a known inhibitor of the complement system and has recently attracted substantial attention due to its role in various diseases, such as cancer, protein-losing enteropathy, and malaria. Some protein-losing enteropathy cases are caused by CD55 deficiency, which leads to complement hyperactivation, malabsorption, and angiopathic thrombosis. In addition, CD55 has been reported to be an essential host receptor for infection by the malaria parasite. Moreover, CD55 is a ligand of the seven-span transmembrane receptor CD97. Since CD55 is present in various cells, the functional role of CD55 has been expanded by showing that CD55 is associated with a variety of diseases, including cancer, malaria, protein-losing enteropathy, paroxysmal nocturnal hemoglobinuria, and autoimmune diseases. This review summarizes the current understanding of CD55 and the role of CD55 in these diseases. It also provides insight into the development of novel drugs for the diagnosis and treatment of diseases associated with CD55.

Mechanisms of Complement-Mediated Damage in Hematological Disorders

The complement cascade is an ancient defense system that destroys and eliminates threats to normal homeostasis in the bloodstream and tissues. Although multiple controls keep complement in check to minimize innocent bystander injury to normal cells and tissues, defects in complement regulation due to mutations in, or autoantibodies to, complement control proteins underlie the pathogenesis of several hemolytic diseases including paroxysmal nocturnal hemoglobinuria, and atypical hemolytic uremic syndrome. In autoimmune hemolytic anemias complement plays an important role in erythrocyte destruction mediated by antierythrocyte antibodies. The pathogenic mechanisms of these hemolytic diseases are discussed, with an emphasis on pivotal steps in complement activation.

Diseases of complement dysregulation-an overview

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.

Acute myeloid leukemia and fatal Scedosporium prolificans sepsis after eculizumab treatment for paroxysmal nocturnal hemoglobinuria: a case report

Eculizumab has become the standard of care for patients with paroxysmal nocturnal hemoglobinuria (PNH). As more patients are treated, the long-term outcomes of these patients will become apparent. We recently treated a patient who developed PNH in the setting of aplastic anemia. The patient developed acute myeloid leukemia less than three years after initiating eculizumab. The patient also died suddenly from Scedosporium sepsis during induction therapy. This patient's course seemed more aggressive than would be expected. The possible effect of complement blockade is discussed.

Proteinase 3 expression on the neutrophils of patients with paroxysmal nocturnal hemoglobinuria

Proteinase 3 (PR3) is released from neutrophils and regulates platelet activity, which is associated with cluster of differentiation (CD)177 antigen (NB1), a glycosylphosphatidylinositol-linked protein. In the present study, the effect of PR3 on thrombosis in paroxysmal nocturnal hemoglobinuria (PNH) and PNH-aplastic anemia (AA) syndrome was explored. The expression of PR3 and NB1 on CD59^- neutrophils was detected by flow cytometry, immunofluorescence (IF), reverse transcription-quantitative polymerase chain reaction analysis and western blotting. Serum levels of PR3, proteinase-activated receptor 1 (PAR1) and D-Dimer were measured using ELISAs. The expression of PR3 and NB1 on the plasma membrane of CD59^- neutrophils in patients with PNH/PNH-AA was significantly lower compared with their expression on CD59⁺ neutrophils in patients and controls (P=0.001). However, no correlation between PR3 and NB1 expression was identified. IF staining further demonstrated partially positive PR3 expression on CD59^- neutrophils. The serum level of PR3 in patients was identified to be significantly decreased compared with healthy controls (P<0.0001), and significantly negatively correlated with PAR1 (r=-0.456; P=0.043) and D-Dimer (r=-0.503; P=0.028) levels. The mRNA and protein levels of PR3 on PNH clones did not change significantly compared with the control group. In conclusion, PR3 expression on the plasma membrane of neutrophils and in the serum of patients with PNH/PNH-AA decreased, which may result in increased PAR1 expression and increased clotting. The present study provides the basis for further study on platelets in PNH.

Clonal evolution in leukemia

Human leukemias are liquid malignancies characterized by diffuse infiltration of the bone marrow by transformed hematopoietic progenitors. The accessibility of tumor cells obtained from peripheral blood or through bone marrow aspirates, together with recent advances in cancer genomics and single-cell molecular analysis, have facilitated the study of clonal populations and their genetic and epigenetic evolution over time with unprecedented detail. The results of these analyses challenge the classic view of leukemia as a clonal homogeneous diffuse tumor and introduce a more complex and dynamic scenario. In this review, we present current concepts on the role of clonal evolution in lymphoid and myeloid leukemia as a driver of tumor initiation, disease progression and relapse. We also discuss the implications of these concepts in our understanding of the evolutionary mechanisms involved in leukemia transformation and therapy resistance.

Efficacy of eculizumab in paroxysmal nocturnal hemoglobinuria patients with or without aplastic anemia: prospective study of a Korean PNH cohort

BACKGROUND

Patients with paroxysmal nocturnal hemoglobinuria (PNH) often have concurrent aplastic anemia (AA). This study aimed to determine whether eculizumab-treated patients show clinical benefit regardless of concurrent AA.

METHODS

We analyzed 46 PNH patients ≥18 years of age who were diagnosed by flow cytometry and treated with eculizumab for more than 6 months in the prospective Korean PNH registry. Patients were categorized into two groups: PNH patients with concurrent AA (PNH/AA, N=27) and without AA (classic PNH, N=19). Biochemical indicators of intravascular hemolysis, hematological laboratory values, transfusion requirement, and PNH-associated complications were assessed at baseline and every 6 months after initiation of eculizumab treatment.

RESULTS

The median patient age was 46 years and median duration of eculizumab treatment was 34 months. Treatment with eculizumab induced rapid inhibition of hemolysis. At 6-month follow-up, LDH decreased to near normal levels in all patients; this effect was maintained until the 36-month follow-up regardless of concurrent AA. Transfusion independence was achieved by 53.3% of patients within the first 6 months of treatment and by 90.9% after 36 months of treatment. The mean number of RBC units transfused was significantly reduced, from 8.5 units during the 6 months prior to initiation of eculizumab to 1.6 units in the first 6 months of treatment, for the total study population; this effect was similar in both PNH/AA and classic PNH.

CONCLUSION

This study demonstrated that eculizumab is beneficial in the management of patients with PNH/AA, similar to classic PNH.

Changing prognosis in paroxysmal nocturnal haemoglobinuria disease subcategories: an analysis of the International PNH Registry

BACKGROUND

Paroxysmal nocturnal haemoglobinuria (PNH) is a rare disease. Although much progress has been made in the understanding of the pathophysiology of the disease, far less is known with respect to the clinical outcomes of patients with PNH. Few retrospective studies provide survival estimates, and even fewer have explored the clinical heterogeneity of the disease. Haemolytic and aplastic anaemia (AA) forms of the disease have been recognised as main disease categories, with the haemolytic form being associated with the worst prognosis by the largest studied cohort some years ago.

AIMS

To describe mortality and causes of death in PNH overall and by PNH classification and to evaluate risk factors associated with mortality.

METHODS

We analysed data of 2356 patients enrolled in the International PNH Registry with multivariate analyses, using time-dependent covariates. Patients were classified into haemolytic, AA/PNH syndrome or intermediate PNH.

RESULTS

Overall, 122 (5.2%) patients died after enrolment, the incidence according to subcategories being 5.1, 11.7, 2.0 and 4.8% for patients with haemolytic PNH, AA-PNH, intermediate and insufficient data respectively. Older age and decreased performance status also affected survival in multivariate analysis. Improved outcome of patients with haemolytic PNH suggests that eculizumab treatment in PNH may be associated with improved survival.

CONCLUSION

A detailed analysis of clinical presentations and causes of death in patients with PNH, overall and by disease subcategories, provide evidence that in the current era, patients with haemolytic PNH are no longer those who harbour the worst prognosis. This finding differs sharply from what has been previously reported.

Outcomes of allogeneic stem cell transplantation in patients with paroxysmal nocturnal hemoglobinuria with or without aplastic anemia

OBJECTIVE

The aim of this study was to evaluate the long-term outcomes of allogeneic stem cell transplantation (SCT) in patients with paroxysmal nocturnal hemoglobinuria (PNH) with or without aplastic anemia (AA).

METHOD

A total of 33 patients with PNH clones who underwent allogeneic SCT were analyzed.

RESULTS

After a median follow-up of 57 months (range, 6.0-151.3), the 5-year estimated overall survival rate was 87.9±5.7%. Four patients died of transplant-related mortality (TRM). With the exception of one patient with early TRM, 32 patients were engrafted. Two patients who had developed delayed GF received a second transplant and recovered. The cumulative incidences of acute graft-vs-host disease (GVHD) (≥grade II) and chronic GVHD (≥moderate) were 27.3±7.9% and 18.7±7.0%, respectively. Twenty-one patients receiving SCT with reduced-intensity conditioning (RIC) had available follow-up data for PNH cell population for the first 6 months post-transplant. Analysis of these data revealed that the PNH clones disappeared within approximately 2 months.

CONCLUSION

RIC regimen was sufficient to eradicate PNH clones with sustained donor-type engraftment after allogeneic SCT. Therefore, application of allogeneic SCT with RIC should be considered in patients with PNH, in accordance with the severity of the underlying bone marrow failure.

Distinct clinical characteristics of paroxysmal nocturnal hemoglobinuria in patients in Southern Taiwan: A multicenter investigation

Paroxysmal nocturnal hemoglobinuria (PNH) is an extremely rare acquired disorder. The aim of this study was to investigate the demographics, clinical manifestations, and outcomes of PNH patients in southern Taiwan. Data on PNH patients diagnosed over a 30-year period (1985-2015) were retrospectively collected from four tertiary medical centers in southern Taiwan. Blood samples were collected for hematologic panel testing and flow cytometry detection of PNH clones. Radiologic studies were performed to assess the frequency of complications. Twenty-four patients were enrolled in this study. The median duration of disease in the study participants was 10.8 years. The median granulocyte PNH clone size was 92.5% (range, 1.3%-99.8%), and the median lactate dehydrogenase (LDH) level was 2920.2 ± 1462.0 IU/L. The incidence of thromboembolism and impaired renal function was 16.7% and 29.2%, respectively. The primary treatment strategies included steroids (79.2%), androgens (42.0%), eculizumab (33.3%), immunosuppressants (16.7%), and anticoagulants (4.2%). In eight patients treated with eculizumab, there was a marked reduction in the LDH levels of 14.89-fold-1.63-fold that of the upper limit of normal; seven patients exhibited decreased transfusion requirements. Twenty-one patients were alive with regular follow-up at the time of publication. Our study demonstrates that PNH patients in southern Taiwan may exhibit different clinical characteristics and outcomes relative to patients in other countries. There was a trend toward a greater PNH granulocyte clone size, which may lead to more hemolysis. In our study, the percentage of patients with impaired renal function, but not the percentage of patients with thrombotic events, was higher than values reported worldwide and in the observational cross-sectional International PNH Registry. More large-scale studies with comprehensive data on the clinical response to different treatments are needed.

Paroxysmal nocturnal haemoglobinuria

Paroxysmal nocturnal haemoglobinuria (PNH) is a clonal haematopoietic stem cell (HSC) disease that presents with haemolytic anaemia, thrombosis and smooth muscle dystonias, as well as bone marrow failure in some cases. PNH is caused by somatic mutations in PIGA (which encodes phosphatidylinositol N-acetylglucosaminyltransferase subunit A) in one or more HSC clones. The gene product of PIGA is required for the biosynthesis of glycosylphosphatidylinositol (GPI) anchors; thus, PIGA mutations lead to a deficiency of GPI-anchored proteins, such as complement decay-accelerating factor (also known as CD55) and CD59 glycoprotein (CD59), which are both complement inhibitors. Clinical manifestations of PNH occur when a HSC clone carrying somatic PIGA mutations acquires a growth advantage and differentiates, generating mature blood cells that are deficient of GPI-anchored proteins. The loss of CD55 and CD59 renders PNH erythrocytes susceptible to intravascular haemolysis, which can lead to thrombosis and to much of the morbidity and mortality of PNH. The accumulation of anaphylatoxins (such as C5a) from complement activation might also have a role. The natural history of PNH is highly variable, ranging from quiescent to life-threatening. Therapeutic strategies include terminal complement blockade and bone marrow transplantation. Eculizumab, a monoclonal antibody complement inhibitor, is highly effective and the only licensed therapy for PNH.

Tissue factor-dependent coagulation activation by heme: A thromboelastometry study

Heme has been characterized as potent trigger of inflammation. In hemostasis, although heme has been shown to both induce and inhibit different compartments of hemostasis, its net effect on the hemostatic balance, and the biological relevance of these effects remain to be determined. Herein we evaluated the effect of heme on hemostasis using a global assay able to generate clinically relevant data in several other complex hemostatic diseases. Citrated whole blood samples from healthy participants were stimulated by heme or vehicle and incubated for 4h at 37°C. Rotational thromboelastometry was immediately performed. The participation of tissue factor in coagulation activation was evaluated using inhibitory antibody. Heme was able of inducing ex vivo coagulation activation in whole blood, affecting predominantly parameters associated with the initial phases of clot formation. This activation effect was at least partially dependent on hematopoietic tissue factor, since the effects of heme were partially abrogated by the inhibition of human tissue factor. In conclusion, using a global hemostasis assay, our study confirmed that heme is able to activate coagulation in whole blood, in a tissue factor-dependent way. These findings could explain the disturbance in hemostatic balance observed in conditions associated with the release of heme such as sickle cell disease.

Clinical course and disease burden in patients with paroxysmal nocturnal hemoglobinuria by hemolytic status

Disease characteristics of patients enrolled in the International PNH Registry were assessed during two follow-up periods based on hemolytic status while untreated with eculizumab: Non-hemolytic cohort: follow-up time defined as time from disease start until last reported untreated lactate dehydrogenase (LDH) value <1.5×upper limit normal (ULN); Hemolytic cohort: follow-up time defined as time from LDH ≥1.5×ULN at or post-disease start, to most recent untreated follow-up. A total of 1012 patients met criteria for the Non-hemolytic cohort and 1565 patients for the Hemolytic cohort; median (min, max) years of follow-up were 2.2 (0.0, 54.2) and 1.2 (0.0, 37.2) years, respectively. Annual rate of thrombotic events (TEs) was lower in the Non-hemolytic than Hemolytic cohort (0.01 events/person-year vs. 0.03 events/person-year; p<0.001). Mortality was lower in the Non-hemolytic cohort than the Hemolytic cohort (0.1% (1 death) vs. 1.8% (22 deaths); p<0.001). While elevated risks for TEs were observed in patients with hemolysis, many TEs were also observed in patients without hemolysis. As thrombosis is the leading cause of mortality in patients with PNH, this real-world analysis highlights the importance of awareness and monitoring for TEs in patients with PNH regardless of hemolytic status.

A retrospective study of paroxysmal nocturnal hemoglobinuria in pediatric and adolescent patients

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare disease, especially in children, characterized by intravascular hemolysis, thrombotic events, serious infections and bone marrow failure. We describe 16 patients who were diagnosed with PNH in childhood or adolescence. The time interval between the onset of symptoms and the PNH diagnosis and its treatment were compared in patients with classic PNH versus PNH associated with bone marrow disorder (PNH/BMD). A greater delay in diagnosis was observed in classic PNH compared to PNH/BMD patients. The first group of patients had higher levels of LDH, total bilirubin and absolute reticulocyte count and a bigger PNH clone size compared to PNH/BMD patients; also thrombotic events were observed only in the classic form of PNH. Conversely, PNH/BMD patients showed lower median levels of platelets. Apart from standard supportive measures, four patients with classic PNH received eculizumab whereas four patients with PNH/BMD underwent hematopoietic stem cell transplantation. Our series confirm that the most frequent presentation of PNH in the pediatric-adolescent age is PNH/BMD. The delay between the onset of symptoms and PNH diagnosis is relevant principally in the classic form. Moreover, our study showed that any case of unexpected thrombosis represents a criterium to perform a PNH screening.

Paroxysmal Nocturnal Hemoglobinuria in the Differential Diagnosis of Thrombocytopenia

Paroxysmal nocturnal hemoglobinuria (PNH) is a disease which diagnosis may be delayed due to variable clinical findings. We describe herein a case of PNH in a 21 year old woman who admitted with complaints of chronic weakness, intermittent spontaneous ecchymoses, and an intermittent abdominal pain. On laboratory tests thrombocytopenia and iron deficiency anemia without any clinical findings were found. Flow cytometric evaluations showed a PNH clone of 15% for erythrocytes, 64% for monocytes, and 60% for granulocytes. The patient was diagnosed with PNH and an eculizumab therapy was initiated. Following initiation of eculizumab therapy, the frequency of abdominal pain attacks decreased, hemoglobin level normalized, and platelet values increased slightly. In patients submitting with a triad of symptoms such as thrombocytopenia, iron deficiency anemia, and abdominal pain attacks of unknown etiology we suggest considering PNH. We also encourage physicians to share their similar observations in order to raise the knowledge on infrequent presentations of PNH.

Renal Manifestations in Paroxysmal Nocturnal Hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired chronic disorder characterized by a triad of clinical features - hemolytic anemia, pancytopenia, and thrombosis. Not many reports of renal involvement in PNH are available in literature. We present a case series of PNH with renal involvement. We present the data of PNH patients who attended to Departments of General Medicine and Nephrology at a government-run tertiary care institute in South India. The diagnosis of PNH in these patients during initial phase, between 1998 and 2004 was based on sucrose lysis and Ham's test. After 2004, the diagnosis was based on flow cytometry to detect CD59 (membrane inhibitor of reactive lysis), a glycoprotein, and CD55 (decay accelerating factor) in regulation of complement action. The patient data were collected from 1998 to 2014. There were 14 patients of PNH in this period. The mean age was 37 years and the range was 16–68 years. There were eight females. Acute kidney injury (AKI) was noted in six patients. Dialysis was performed in four of them. The mean serum creatinine and urea at the initiation of dialysis were 5.4 ± 0.6 and 64.1 ± 6.1 mg/dl, respectively. The median number of hemodialysis sessions done was four. Renal biopsy was done in four patients. In three patients, the urinalysis and serum chemistry were suggestive of Fanconi syndrome. In our patients, three renal manifestations of PNH were identified. They were AKI, renal vessel thrombosis, and Fanconi syndrome. Chronic renal failure was not identified.

Management of thrombosis in paroxysmal nocturnal hemoglobinuria: a clinician's guide

Paroxysmal nocturnal haemoglobinuria (PNH), an ultra-orphan disease with a prevalence of 15.9 per million in Europe, is a life-threatening disorder, characterized by haemolysis, bone marrow failure and thrombosis. Patients with PNH prior to the availability of eculizumab had a median survival of between 10 and 22 years, with thrombosis accounting for 22-67% of deaths. 29-44% of patients had at least one thrombosis. This paper provides a clinician's guide to the diagnosis, management and complications of PNH, with an emphasis on thrombosis.

Review article: the aetiology of primary Budd-Chiari syndrome - differences between the West and China

BACKGROUND

China may have the largest number of Budd-Chiari syndrome (BCS) cases in the world (at least 1914 original papers were published, and at least 20 191 BCS patients were reported). Considering the discrepancy in the clinical profiles and preferred treatment selection of primary BCS between the West and China, understanding its aetiology in these two different regions is very important.

AIM

To review the data from large cohort studies and meta-analyses to illustrate the epidemiology of risk factors for BCS in the West and China.

METHODS

Relevant papers were identified by major English- and Chinese-language databases, conference abstracts, and by manual search.

RESULTS

Risk factors reviewed include myeloproliferative neoplasms (MPNs) and their related gene mutations, anti-phospholipid syndrome, paroxysmal nocturnal haemoglobinuria (PNH), hyperhomocysteinaemia and 5,10-methylenetetrahydrofolate reductase (MTHFR) C677T mutation, factor V Leiden (FVL) and prothrombin G20210A mutations, inherited anti-thrombin, protein C and protein S deficiencies, pregnancy and puerperium, poverty, and family history.

CONCLUSIONS

We examined the differences in the aetiological distribution of BCS between the West and China. Several recommendations should be considered in Chinese BCS patients: (i) screening for hyperhomocysteinaemia and MTHFR mutation should be regularly performed; (ii) screening for MPNs, PNH, and anti-phospholipid syndrome should be selectively performed; (iii) inherited anti-thrombin, protein C, and protein S deficiencies should be actively explored; (iv) screening for FVL and prothrombin G20210A mutations may be unnecessary; and (v) the clinical significance of pregnancy and puerperium, poverty with bacterial infections and unsanitary environments, and family history as possible risk factors should never be neglected.

Development of a disease-specific quality of life questionnaire for patients with aplastic anemia and/or paroxysmal nocturnal hemoglobinuria (QLQ-AA/PNH)-report on phases I and II

Acquired aplastic anemia (AA) and paroxysmal nocturnal hemoglobinuria (PNH) are interrelated ultra-rare diseases. Quality of life (QoL) evaluation tools used in studies for AA and PNH are unspecific and designed for cancer patients (e.g., the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire, EORTC QLQ-C30). Given the complexity of AA and PNH, variation in symptoms and treatments, younger age of many patients, and the fact that AA and PNH are not classified as malignant diseases, it is likely that cancer-specific questionnaires are inappropriate. We generate an AA/PNH-specific QoL questionnaire (QLQ-AA/PNH), performed according to EORTC guidelines. QoL issues were obtained from the literature and interviews with patients and physicians (phase I), then ranked by patients and physicians. In phase II, items were created. Patients in more than 25 German and Swiss cities were interviewed face to face. In phase I, interviews of 19 patients and 8 physicians specialized in AA/PNH treatment resulted in 649 QoL issues; these were condensed to 175 and graded according to their importance by 30 patients and 14 physicians (phase II). Five physicians took part in phases I and II. Altogether, 97 issues were rated important. Twelve EORTC QLQ-C30 items were not rated important, while several new QoL aspects were brought up. Modifications in wording and phrasing led to two questionnaires with 77 items regarding general QoL aspects and 20 items regarding medical care. Important QoL aspects of PNH/AA patients are inappropriately captured with available QoL tools. Developing a new QoL questionnaire specific for this patient group is warranted.