The pathophysiology of disease in patients with paroxysmal nocturnal hemoglobinuria

Pharmacokinetics, pharmacodynamics, efficacy, and safety of ravulizumab in pediatric paroxysmal nocturnal hemoglobinuria

ABSTRACT

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare hematologic disease of uncontrolled terminal complement activation leading to intravascular hemolysis, thrombotic events and increased morbidity and mortality. This phase 3, open-label, single-arm, multicenter study evaluated ravulizumab treatment in eculizumab-naive or -experienced pediatric patients (aged <18 years) with PNH over a 26-week primary evaluation period (PEP) and 4-year extension period (EP). Patients included in the study received weight-based intravenous ravulizumab dosing. Primary end points were pharmacokinetic and pharmacodynamic parameters to confirm complement component 5 (C5) inhibition by ravulizumab; secondary end points assessed the efficacy (including percentage change in lactate dehydrogenase levels over time) and safety of ravulizumab. Thirteen patients, 5 (38.5%) eculizumab-naive and 8 (61.5%) eculizumab-experienced, were enrolled. Ravulizumab Ctrough levels were above the pharmacokinetic threshold of 175 μg/mL in the PEP and EP except in 1 patient. At the end of the study, pre- and post-infusion mean ± standard deviation serum ravulizumab concentrations were 610.50 ± 201.53 μg/mL and 518.29 ± 109.67 μg/mL for eculizumab-naive and eculizumab-experienced patients, respectively. After the first ravulizumab infusion, serum-free C5 concentrations were <0.5 μg/mL in both cohorts until the end of the study (0.061 ± 0.021 μg/mL and 0.061 ± 0.018 μg/mL for eculizumab-naive and eculizumab-experienced patients, respectively). Compared with baseline, ravulizumab improved and maintained efficacy outcomes in both groups. Ravulizumab had an acceptable safety profile with no new safety signals identified, and provided immediate, complete, and sustained terminal complement inhibition, translating to clinical benefit for pediatric patients with PNH. This trial was registered at www.ClinicalTrials.gov as #NCT03406507.

Clinical guidelines for the management of patients with paroxysmal nocturnal hemoglobinuria

Introduction. Paroxysmal nocturnal hemoglobinuria (PNH) is a rare acquired clonal disease of the blood system characterized by intravascular hemolysis, bone marrow dysfunction and an increased risk of thrombotic and organ complications.

Aim — to provide relevant clinical recommendations for the provision of medical care to adults and children with PNH.

Basic information. Experts from the National Hematological Society association which is focused on the promotion of hematology, transfusiology and bone marrow transplantation along with experts from the public organization, National Society of Pediatric Hematologists and Oncologists, have developed current clinical recommendations for providing medical care to adults and children with PNH. The recommendations address in detail the issues of etiology, pathogenesis, epidemiology, and clinical manifestations of the disease. Special attention is paid to the diagnosis, differential diagnosis, and treatment of PNH based on the principles of evidence.

Pediatric Paroxysmal Nocturnal Hemoglobinuria Presenting as Acute Kidney Injury

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare disease characterized by variable and diverse symptoms including the classic triad of hemolytic anemia, thrombosis, and bone marrow failure. It is a disorder primarily seen in the adult population. The authors report a unique case of an 8-year-old girl diagnosed with PNH after initially presenting with a febrile illness and acute kidney injury. Though rare in children, PNH should remain in the differential diagnosis of a child presenting with acute kidney injury. The disease has serious long-term complications, mandating timely diagnosis and appropriate therapy.

Bone Marrow Failure Syndromes, Overlapping Diseases with a Common Cytokine Signature

Bone marrow failure (BMF) syndromes are a heterogenous group of non-malignant hematologic diseases characterized by single- or multi-lineage cytopenia(s) with either inherited or acquired pathogenesis. Aberrant T or B cells or innate immune responses are variously involved in the pathophysiology of BMF, and hematological improvement after standard immunosuppressive or anti-complement therapies is the main indirect evidence of the central role of the immune system in BMF development. As part of this immune derangement, pro-inflammatory cytokines play an important role in shaping the immune responses and in sustaining inflammation during marrow failure. In this review, we summarize current knowledge of cytokine signatures in BMF syndromes.

Rare Hematological Disease of Paroxysmal Nocturnal Hemoglobinuria With Profound Implications for a Gastroenterologist: A Case Report and Literature Review

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare type of thrombophilia and hematopoietic stem cell disorder characterized by mutation of the X-linked PIG-A gene. Patients with PNH present either with clinical features of intravascular hemolysis or thrombosis. Visceral vein thrombosis is associated with increased mortality risk. Here, we present an extremely rare case of a young man presenting with extensive thrombosis of multiple visceral veins from PNH.

Identification of acquired PIGA mutations and additional variants by next-generation sequencing in paroxysmal nocturnal hemoglobinuria

INTRODUCTION

Paroxysmal Nocturnal Hemoglobinuria (PNH) is an acquired clonal disease of hematopoietic stem cells. It is caused by somatic mutation of the X-linked PIGA gene, resulting in a deficient expression of glycosylphosphatidylinositol-anchored proteins (GPI-APs). In this study, we aimed to explore the diagnostic value of next-generation sequencing (NGS) and potential molecular basis in PNH patients.

METHODS

Genomic DNA of 85 PNH patients was analyzed by a 114-gene NGS panel.

RESULTS

Mutational analysis of PIGA identified 124 mutations in 92% PNH patients, including 101 distinct mutations and 23 recurrent mutations. Among them, 102 mutations were newly reported. Most mutations were located in exon 2 of PIGA gene, and truncated mutation was the most common one. Other mutations were detected in 26 out of 85 cases, including five cases of DNMT3A variants, four cases of ASXL1 variants, and four cases of U2AF1 variants. Clonal analysis was performed in one case and outlined a linear evolution pattern in classic PNH. There was a positive correlation between number of PIGA mutations and fraction of GPI-APs deficient granulocytes.

CONCLUSION

The detection of PIGA mutations and additional variants by targeted NGS not only shed light on the genetic characteristics of PNH, but also provided an important reference value in the diagnosis of PNH at molecular level.

Autosplenectomy in a Patient with Paroxysmal Nocturnal Hemoglobinuria (PNH)

Autosplenectomy (AS) is a known complication of diseases such as sickle cell anemia, celiac disease, and inflammatory bowel disease. We report the first known case of AS due to paroxysmal nocturnal hemoglobinuria (PNH). A 24-year-old Caucasian male had evidence of hemolytic anemia at the age of 14 and was diagnosed with PNH at the age of 16. He had recurrent episodes of sepsis due to dialysis line infections from poor hygiene, and blood cultures had been positive for multiple organisms including Staphylococcus aureus, Enterococcus faecalis, and Streptococcus pneumoniae. The patient's peripheral blood smears since the age of 14 years demonstrated Howell–Jolly bodies in conjunction with thrombocytopenia and hemolytic anemia, but abdominal ultrasonography reported a normal appearing spleen. The patient presented with septicemia two years after starting eculizumab, and his peripheral blood smear showed extensive Howell–Jolly bodies, Pappenheimer bodies, acanthocytes, and target cells. Splenic ultrasonography demonstrated an atrophic spleen with multifocal scarring, and absent splenic uptake of liver-spleen scintigraphy, consistent with AS. Clinicians should remain vigilant of the potential sequelae of PNH and consider the possibility of the development of AS.

Diagnosis of Paroxysmal Nocturnal Hemoglobinuria: Recent Advances

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal hematopoietic stem cell disorder with its protean clinical manifestations. This is due to partial or complete absence of 'glycophosphatidyl-inositol-anchor proteins' (GPI-AP). The main aim of this review is to highlight various diagnostic modalities available, basic principle of each test and recent advances in the diagnosis of PNH. Recently among various tests available, the flow cytometry has become 'the gold standard' for PNH testing. In order to overcome the difficulties encountered by the testing and research laboratories throughout the world, International Clinical Cytometry Society has come up with guidelines regarding the indications for testing, protocol for sample collection, processing, panel of antibodies as well as gating strategies to be used, how to interpret the test and reporting format to be used. It is essential to test at least two GPI-linked markers on at least two different lineages particularly on red cells and granulocytes/monocytes. The fluorescent aerolysin combined with other monoclonal antibodies in multicolour flow cytometry offered an improved assay not only for diagnosis but also for monitoring of PNH clones. It is equally important to diagnose this rare entity with high index of suspicion.

Paroxysmal Nocturnal Hemoglobinuria: From Bench to Bed

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired hemolytic anemia with highly variable clinical symptoms making the diagnosis and prediction of its outcome difficult. It is caused by the expansion of a hematopoietic progenitor cell that has acquired a mutation in the X-linked phosphatidylinositol glycan class A (PIGA) gene that results in deficiency of the glycosylphosphatidylinositol anchor structure responsible for fixing a wide spectrum of proteins particularly CD55 and CD59. The clinical features of this disease arise as a result of complement-mediated hemolysis in unprotected red cells, leukocytes, and platelets as well as the release of free hemoglobin. Patients may present with a variety of clinical manifestations, such as anemia, thrombosis, kidney disease, smooth muscle dystonias, abdominal pain, dyspnea, and extreme fatigue. PNH is an outstanding example of how an increased understanding of pathophysiology may directly improve clinical symptoms and treat disease-associated complications when we inhibit the terminal complement cascade. This topic will discuss PNH overview to assist specialists looking after PNH patients.

Flow cytometry screening for paroxysmal nocturnal hemoglobinuria: A single-center experience in Saudi Arabia

BACKGROUND

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare acquired clonal hematopoietic stem cell disorder, characterized by the deficiency of glycosylphosphatidylinositol (GPI) that anchors proteins in cell membranes. PNH is manifest variously with hemoglobinuria, thrombosis, or bone marrow failure. This retrospective study was aimed at assessing the incidence and characteristics of patients diagnosed with PNH in the King Fisal Specialist Hospital and research center.

METHODS

Patients referred for PNH diagnosis at King Faisal Specialist Hospital and Research Centre, Riyadh, during the 2-year period (2012-2013) were included in the analysis. Peripheral blood samples were used for multi-parametric flow cytometry analysis based on fluorescent inactive aerolysin (FLAER), and the markers, CD235a and CD59 on red blood cells (RBCs), and CD14, CD45, CD64, CD24, and CD15 on white blood cells (WBCs) exclusively monocytes and granulocytes. Univariate analysis of the disease characteristics was performed.

RESULTS

Of the 366 samples submitted for PNH screening, 14 were positive (4%) and 11 were evaluable. Of the 11 patients analyzed, 8 patients (73%) presented with aplastic anemia, 1 patient (9%) each with pancytopenia, Budd-Chiari syndrome, and immune thrombocytopenia purpura. All samples showed type II and III GPI-deficient clones with a median clone size of 15% (range, 0.7%-56%) in the RBCs, and 63% (range, 3.8%-100%) in WBCs (monocytes and granulocytes).

CONCLUSIONS

This study confirms the rarity of PNH and its predominant presentation as aplastic anemia or thrombosis in a Saudi Arabian population, similar to the worldwide incidence.

The role of bioactive lipids in stem cell mobilization and homing: novel therapeutics for myocardial ischemia

Despite significant advances in medical therapy and interventional strategies, the prognosis of millions of patients with acute myocardial infarction (AMI) and ischemic heart disease (IHD) remains poor. Currently, short of heart transplantation with all of its inherit limitations, there are no available treatment strategies that replace the infarcted myocardium. It is now well established that cardiomyocytes undergo continuous renewal, with contribution from bone marrow (BM)-derived stem/progenitor cells (SPCs). This phenomenon is upregulated during AMI by initiating multiple innate reparatory mechanisms through which BMSPCs are mobilized towards the ischemic myocardium and contribute to myocardial regeneration. While a role for the SDF-1/CXCR4 axis in retention of BMSPCs in bone marrow is undisputed, its exclusive role in their mobilization and homing to a highly proteolytic microenvironment, such as the ischemic/infarcted myocardium, is currently being challenged. Recent evidence suggests a pivotal role for bioactive lipids in the mobilization of BMSPCs at the early stages following AMI and their homing towards ischemic myocardium. This review highlights the recent advances in our understanding of the mechanisms of stem cell mobilization, provides newer evidence implicating bioactive lipids in BMSPC mobilization and differentiation, and discusses their potential as therapeutic agents in the treatment of IHD.

Reticulate dermatoses

The term "reticulate" is used for clinical description of skin lesions that are configured in a net-like pattern. Many primary and secondary dermatoses present in such patterns involving specific body sites. Certain cutaneous manifestations of systemic diseases or genodermatoses also present in such manner. This review classifies and describes such conditions with reticulate lesions and briefly, their associated features.

Frequency of paroxysmal nocturnal hemoglobinuria in patients attended in Belém, Pará, Brazil

BACKGROUND

Paroxysmal nocturnal hemoglobinuria is a hematological disease with complex physiopathology. It is genetically characterized by a somatic mutation in the PIG-A gene (phosphatidylinositol glycan anchor biosynthesis, class A), in which the best known antigens are DAF (decay accelerating factor or CD55) and MIRL (membrane inhibitor of reactive lysis or CD59).

OBJECTIVE

To determine the frequency of paroxysmal nocturnal hemoglobinuria in patients attended at the HEMOPA foundation from November 2008 to July 2009.

METHOD

Thirty patients, with ages ranging from two to 79 years old and suspected of having paroxysmal nocturnal hemoglobinuria were examined. All patients were immunophenotyped by flow cytometry for the CD5, CD59, CD16 and CD45 antigens.

RESULTS

Paroxysmal nocturnal hemoglobinuria was identified in nine of the thirty patients investigated. Another 3 cases had inconclusive results with CD59-negative labeling only for neutrophils. The highest frequency of paroxysmal nocturnal hemoglobinuria patients (7/9) and inconclusive cases (2/3) were between 19 years old and 48 years old, with a median of 28 years.

CONCLUSION

These results show the importance of flow cytometry to identify cases in which patients are deficient in only one antigen (CD59).

Paroxysmal nocturnal hemoglobinuria in pediatric patients

BACKGROUND

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare disease in children. The most significant clinical features of PNH include: bone marrow failure, intravascular hemolysis, and thrombosis. To further characterize the clinical presentation and outcome to treatment we performed a retrospective analysis of pediatric patients with PNH.

PROCEDURE

We reviewed the medical records of 12 consecutive pediatric patients with PNH diagnosed at our institution from 1992 to 2010.

RESULTS

Presenting clinical symptoms included: bone marrow failure (N = 10); gross hemoglobinuria with isolated red cell anemia (N = 1); and jaundice, hepatitis, and isolated thrombocytopenia (N = 1). Immunosuppressive therapy was the initial treatment for 8 patients. Five patients had myelodysplastic features without developing excessive blasts or leukemic transformation. Thrombosis occurred in 6 patients. Five patients underwent hematopoietic stem cell transplant (HSCT) of whom 3 patients are alive and disease-free. Three patients received anti-complement therapy with eculizumab. Two patients died following complications related to thrombosis and 2 patients are transfusion independent with stable disease.

CONCLUSION

This report highlights a high rate of bone marrow failure along with a low rate of hemoglobinuria at presentation, a high rate of thrombosis, and for some patients the spontaneous resolution of myelodysplastic features. Delay in diagnosis is common and we recommend appropriate PNH testing in all patients with AA, MDS, unexplained Coombs-negative hemolysis, or thrombosis. While HSCT remains the only curative option the high prevalence of hemolysis and thrombosis should warrant the consideration of early treatment with anti-complement therapy.

To stay or to leave: Stem cells and progenitor cells navigating the S1P gradient

Most hematopoietic stem progenitor cells (HSPCs) reside in bone marrow (BM), but a small amount of HSPCs have been found to circulate between BM and tissues through blood and lymph. Several lines of evidence suggest that sphingosine-1-phosphate (S1P) gradient triggers HSPC egression to blood circulation after mobilization from BM stem cell niches. Stem cells also visit certain tissues. After a temporary 36 h short stay in local tissues, HSPCs go to lymph in response to S1P gradient between lymph and tissue and eventually enter the blood circulation. S1P also has a role in the guidance of the primitive HSPCs homing to BM in vivo, as S1P analogue FTY720 treatment can improve HSPC BM homing and engraftment. In stress conditions, various stem cells or progenitor cells can be attracted to local injured tissues and participate in local tissue cell differentiation and tissue rebuilding through modulation the expression level of S1P₁, S1P₂ or S1P₃ receptors. Hence, S1P is important for stem cells circulation in blood system to accomplish its role in body surveillance and injury recovery.

Novel insight into stem cell mobilization-plasma sphingosine-1-phosphate is a major chemoattractant that directs the egress of hematopoietic stem progenitor cells from the bone marrow and its level in peripheral blood increases during mobilization due to activation of complement cascade/membrane attack complex

Complement cascade (CC) becomes activated and its cleavage fragments play a crucial role in the mobilization of hematopoietic stem/progenitor cells (HSPCs). Here, we sought to determine which major chemottractant present in peripheral blood (PB) is responsible for the egress of HSPCs from the BM. We noticed that normal and mobilized plasma strongly chemoattracts HSPCs in a stromal derived factor-1 (SDF-1)-independent manner because i) plasma SDF-1 level does not correlate with mobilization efficiency, ii) the chemotactic plasma gradient is not affected in the presence of AMD3100, and iii) it is resistant to denaturation by heat. Surprisingly, the observed loss of plasma chemotactic activity after charcoal stripping suggested involvement of bioactive lipids and we focused on sphingosine-1 phosphate (S1P), a known chemoattracant of HSPCs. We found that S1P i) creates in plasma a continuously present gradient for BM-residing HSPCs, ii) is at physiologically relevant concentrations a chemoattractant several magnitudes stronger than SDF-1, and iii) its plasma level increases during mobilization due to CC activation and the interaction of membrane attack complex (MAC) with erythrocytes that are a major reservoir of S1P. We conclude and propose a new paradigm that S1P is a crucial chemoattractant for BM-residing HSPCs and that CC via MAC induces release of S1P from erythrocytes for optimal egress/mobilization of HSPCs.

Novel insight into stem cell mobilization-plasma sphingosine-1-phosphate is a major chemoattractant that directs the egress of hematopoietic stem progenitor cells from the bone marrow and its level in peripheral blood increases during mobilization due to activation of complement cascade/membrane attack complex

We reported that complement cascade (CC) becomes activated in bone marrow (BM) during mobilization of hematopoietic stem/progenitor cells (HSPCs) induced by granulocyte-colony stimulating factor (G-CSF) and C5 cleavage plays an important role in optimal egress of HSPCs. In the current work, we explored whether CC is involved in mobilization of HSPCs induced by the CXCR4 antagonist, AMD3100. To address this question, we performed mobilization studies in mice that display a defect in the activation of the proximal steps of CC (Rag^−/−, SCID, C2.Cfb^−/−) as well as in mice that do not activate the distal steps of CC (C5^−/−). We noticed that proximal CC activation-deficient mice (above C5 level), in contrast to distal step CC activation-deficient C5^−/− ones mobilize normally in response to AMD3100 administration. We hypothesized that this discrepancy in mobilization could be explained by AMD3100 activating C5 in Rag^−/−, SCID, C2.Cfb^−/− animals in a non-canonical mechanism involving activated granulocytes. To support this granulocytes i) as first egress from BM and ii) secrete several proteases that cleave/activate C5 in response to AMD3100. We conclude that AMD3100-directed mobilization of HSPCs, similarly to G-CSF-induced mobilization, depends on activation of CC; however, in contrast to G-CSF, AMD3100 activates the distal steps of CC directly at the C5 level. Overall, these data support that C5 cleavage fragments and distal steps of CC activation are required for optimal mobilization of HSPCs.