Small Paroxysmal Nocturnal Hemoglobinuria Clones in Autoimmune Hemolytic Anemia: Clinical Implications and Different Cytokine Patterns in Positive and Negative Patients

Overview on Hereditary Spherocytosis Diagnosis

INTRODUCTION

Hereditary spherocytosis (HS) is a congenital haemolytic disorder, resulting from plasma membrane protein deficiency of red blood cells (RBCs). Typical pathological signs are anemia, jaundice, and splenomegaly; in newborns, jaundice is the main symptom.

MATERIAL AND METHODS

This study focused on the state of art about the HS diagnosis, from traditional to innovative methods, including diagnostic algorithms that can be applied for pediatric and adult patients, for different laboratory diagnostic levels.

RESULTS

The first erythrocyte parameters used for HS diagnosis were the mean corpuscular hemoglobin concentration (MCHC), mean corpuscular volume (MCV), and red blood cell distribution width (RDW); nowadays new parameters are used in blood cell counter. Advia analyzers (Siemens Medical Solutions) supply the hyper-dense cell percentage (% Hyper), which reflects the red blood cells hyperchromia. Sysmex instruments (i.e. XT-4000i, XE-5000, XN-Series) provide the MicroR, that is the percentage of erythrocytes smaller than 60 fL, Hypo-He, which is the percentage of erythrocytes with a content of hemoglobin less than 17 pg and % Hyper-He, which represents the percentage of RBC with cellular hemoglobin content higher than 49 pg. CELL-DYN Sapphire (Abbott Diagnostics) introduced the HPR parameter (% HPR), which represents the erythrocytes with hemoglobin > 410 g/L. Beckman Coulter instruments supply the mean sphered corpuscular volume (MSCV), which is the average volume of all erythrocytes, including mature erythrocytes and reticulocytes. Other reference tests for screening and diagnosis of HS are the acidified glycerol lysis test (AGLT), the eosin-5-maleimide (EMA) binding test and genetic testing by next-generation sequencing.

CONCLUSIONS

The diagnostic workup of hereditary spherocytosis could be improved thanks to all the available tests, including new molecular tools. However, it requires synergy between clinicians and laboratory staff, evaluating clinical manifestations, all available data related to the disease and the prognosis to fill the diagnostic gaps in the near future.

Autoimmune Hemolytic Anemias: Challenges in Diagnosis and Therapy

Background

Autoimmune hemolytic anemia (AIHA) is a rare disease due to increased destruction of erythrocytes by autoantibodies, with or without complement activation.

Summary

AIHA is usually classified in warm AIHA (wAIHA) and cold agglutinin disease (CAD), based on isotype and thermal amplitude of the autoantibody. The direct antiglobulin test (DAT) or Coombs test is the cornerstone of AIHA diagnosis, as it is positive with anti-IgG in wAIHA, and with anti-C3d/IgM antisera plus high titer cold agglutinins in CAD. Therapy is quite different, as steroids and rituximab are effective in the former, but have a lower response rate and duration in the latter. Splenectomy, which is still a good option for young/fit wAIHA, is contraindicated in CAD, and classic immunosuppressants are moving to further lines. Several new drugs are increasingly used or are in trials for relapsed/refractory AIHAs, including B-cell (parsaclisib, ibrutinib, rilzabrutinib), and plasma cell target therapies (bortezomib, daratumumab), bispecific agents (ianalumab, obexelimab, povetacicept), neonatal Fc receptor blockers (nipocalimab), and complement inhibitors (sutimlimab, riliprubart, pegcetacoplan, iptacopan). Clinically, AIHAs are highly heterogeneous, from mild/compensated to life-threatening/fulminant, and may be primary or associated with infections, neoplasms, autoimmune diseases, transplants, immunodeficiencies, and drugs. Along with all these variables, there are rare forms like mixed (wAIHA plus CAD), atypical (IgA or warm IgM driven), and DAT negative, where the diagnosis and clinical management are particularly challenging.

Key Messages

This article covers the classic clinical features, diagnosis, and therapy of wAIHA and CAD, and focuses, with the support of clinical vignettes, on difficult diagnosis and refractory/relapsing cases requiring novel therapies.

Deciphering Paroxysmal Nocturnal Hemoglobinuria: An Unusual Paradigm of Hemolytic Anemia

Paroxysmal nocturnal hemoglobinuria (PNH), a clonal hematopoietic stem cell disorder, arises from the increased sensitivity of red blood cells (RBC) to complement due to an acquired deficiency of certain glycosylphosphatidylinositol (GPI)-linked proteins, resulting in chronic intravascular hemolysis, arterial and venous thrombotic phenomena, multi-organ damage, and failure. We present an intriguing case of hemolytic anemia, initially suspected to be drug-induced, and later found to be associated with PNH, despite being a subclinical clone. A clinician should not hesitate to repeat fluorescent-labeled aerolysin (FLAER) cytometry if the clinical picture strongly favors a diagnosis of PNH. This case marks the importance of testing for PNH clones in autoimmune hemolytic anemia (AIHA) since their prevalence is not negligible and may correspond to a prominent hemolytic pattern, a higher thrombotic risk, and a higher therapeutic indication, such as eculizumab. This underscores the significance of conducting a thorough evaluation for occult causes of treatment-unresponsive hemolytic anemia, paving options for an early and alternative therapeutic approach.

Swiss Survey on current practices and opinions on clinical constellations triggering the search for PNH clones

This national survey investigated the current practice in Switzerland by collecting participants' opinions on paroxysmal nocturnal hemoglobinuria (PNH) clone assessment and clinical practice.

Aim

This study aimed to investigate clinical indications prompting PNH clones' assessment and physician's accessibility of a flow cytometry facility, and also to understand clinical attitudes on the follow-up (FU) of patients with PNH clones.

Methods

The survey includes 16 multiple-choice questions related to PNH and targets physicians with a definite level of experience in the topic using two screener questions. Opinion on clinical management was collected using hypothetical clinical situations. Each participant had the option of being contacted to further discuss the survey results. This was an online survey, and 264 physicians were contacted through email once a week for 5 weeks from September 2020.

Results

In total, 64 physicians (24.2%) from 23 institutions participated (81.3% hematologists and 67.2% from university hospitals). All had access to flow cytometry for PNH clone testing, with 76.6% having access within their own institution. The main reasons to assess for PNH clones were unexplained thrombosis and/or hemolysis, and/or aplastic anemia (AA). Patients in FU for PNH clones were more likely to be aplastic anemia (AA) and symptomatic PNH. In total, 61% of the participants investigated PNH clones repetitively during FU in AA/myelodysplastic syndromes patients, even when there was no PNH clone found at diagnosis, and 75% of the participants tested at least once a year during FU. Opinions related to clinical management were scattered.

Conclusion

The need to adhere to guidelines for the assessment, interpretation, and reporting of PNH clones emerges as the most important finding, as well as consensus for the management of less well-defined clinical situations. Even though there are several international guidelines, clear information addressing specific topics such as the type of anticoagulant to use and its duration, as well as the indication for treatment with complement inhibitors in some borderline situations are needed. The analysis and the discussion of this survey provide the basis for understanding the unmet needs of PNH clone assessment and clinical practice in Switzerland.

Autoimmunity: Are we asking the right question?

For decades, the main question immunologists have asked about autoimmunity is "what causes a break in self-tolerance?" We have not found good answers to that question, and I believe we are still so ignorant because it's the wrong question. Rather than a break in self-tolerance, I suggest that many autoimmune diseases might be due to defects in normal tissue physiology.

Intravascular hemolysis and multitreatment predict thrombosis in patients with autoimmune hemolytic anemia

BACKGROUND

Thrombosis may complicate autoimmune hemolytic anemia (AIHA), but its predictors are still lacking, and no clear-cut indications for anticoagulant prophylaxis are available.

OBJECTIVES

To characterize frequency and severity of thromboses in AIHA patients and identify risk factors for thrombosis that may advise primary anticoagulant prophylaxis.

PATIENTS/METHODS

A total of 287 consecutive AIHA patients diagnosed and followed from 1978 at a tertiary Italian center were retrospectively studied; 174 of them were prospectively evaluated from January 2020 until December 2021. AIHA relapse, thrombosis occurrence, and primary anticoagulant prophylaxis were evaluated.

RESULTS

Thirty-three AIHA patients (11.4%) experienced thrombosis, 70% of whom hospitalized. The cumulative thrombosis incidence was higher in patients with lactate dehydrogenase (LDH) ≥ 1.5 (hazard ratio [HR] 3.22), in those experiencing infections (HR 3.57), receiving transfusions (HR 3.06), rituximab (HR 3.3), or cyclophosphamide (HR 2.67). By multivariable analysis, LDH, transfusions, rituximab, and cyclophosphamide treatment emerged as independent factors associated with thrombosis. Among 174 patients prospectively followed in the past 2 years, we observed 70 acute hemolytic episodes in 45 patients; 33/45 displayed LDH ≥1.5 × upper limit of normal, and 17 received anticoagulant prophylaxis with low molecular weight heparin for a median of 70 days (30-300). In those receiving prophylaxis no thrombotic complications occurred, whereas five thrombotic episodes were registered in the remaining 16 cases.

CONCLUSIONS

Thrombosis was observed in about 11% of AIHA patients, mainly grade 3, and associated with intravascular hemolysis, need of transfusions, multitreatment, and infections, advising primary anticoagulant prophylaxis in these settings.

Autoimmune hemolytic anemia: causes and consequences

INTRODUCTION

Autoimmune hemolytic anemia (AIHA) is classified according to the direct antiglobulin test (DAT) and thermal characteristics of the autoantibody into warm and cold forms, and in primary versus secondary depending on the presence of associated conditions.

AREAS COVERED

AIHA displays a multifactorial pathogenesis, including genetic (association with congenital conditions and certain mutations), environmental (drugs, infections, including SARS-CoV-2, pollution, etc.), and miscellaneous factors (solid/hematologic neoplasms, systemic autoimmune diseases, etc.) contributing to tolerance breakdown. Several mechanisms, such as autoantibody production, complement activation, monocyte/macrophage phagocytosis, and bone marrow compensation are implicated in extra-/intravascular hemolysis. Treatment should be differentiated and sequenced according to AIHA type (i.e. steroids followed by rituximab for warm, rituximab alone or in association with bendamustine or fludarabine for cold forms). Several new drugs targeting B-cells/plasma cells, complement, and phagocytosis are in clinical trials. Finally, thrombosis and infections may complicate disease course burdening quality of life and increasing mortality.

EXPERT OPINION

Beyond warm and cold AIHA, a gray-zone still exists including mixed and DAT negative forms representing an unmet need. AIHA management is rapidly changing through an increasing knowledge of the pathogenic mechanisms, the refinement of diagnostic tools, and the development of novel targeted and combination therapies.

Paroxysmal Nocturnal Hemoglobinuria in the Context of a Myeloproliferative Neoplasm: A Case Report and Review of the Literature

Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by intravascular hemolytic anemia and thrombosis and is notoriously associated with aplastic anemia and myelodysplastic syndromes. Rarer associations include myeloproliferative neoplasms (MPNs), which are also burdened by increased thrombotic tendency. The therapeutic management of this rare combination has not been defined so far. Here, we describe a 62-year-old man who developed a highly hemolytic PNH more than 10 years after the diagnosis of MPN. The patient started eculizumab, obtaining good control of intravascular hemolysis but without amelioration of transfusion-dependent anemia. Moreover, we performed a review of the literature regarding the clinical and pathogenetic significance of the association of PNH and MPN. The prevalence of PNH clones in MPN patients is about 10%, mostly in association with JAK2V617F-positive myelofibrosis. Thrombotic events were a common clinical presentation (35% of subjects), sometimes refractory to combined treatment with cytoreductive agents, anticoagulants, and complement inhibitors. The latter showed only partial effectiveness in controlling hemolytic anemia and, due to the paucity of data, should be taken in consideration after a careful risk/benefit evaluation in this peculiar setting.

Immune Phenomena in Myeloid Neoplasms: An "Egg or Chicken" Question

Immune phenomena are increasingly reported in myeloid neoplasms, and include autoimmune cytopenias/diseases and immunodeficiency, either preceding or complicating acute myeloid leukemia, myelodysplastic syndromes (MDS), chronic myeloproliferative neoplasms, and bone marrow failure (BMF) syndromes. Autoimmunity and immunodeficiency are the two faces of a dysregulated immune tolerance and surveillance and may result, along with contributing environmental and genetic factors, in an increased incidence of both tumors and infections. The latter may fuel both autoimmunity and immune activation, triggering a vicious circle among infections, tumors and autoimmune phenomena. Additionally, alterations of the microbiota and of mesenchymal stem cells (MSCs) pinpoint to the importance of a permissive or hostile microenvironment for tumor growth. Finally, several therapies of myeloid neoplasms are aimed at increasing host immunity against the tumor, but at the price of increased autoimmune phenomena. In this review we will examine the epidemiological association of myeloid neoplasms with autoimmune diseases and immunodeficiencies, and the pivotal role of autoimmunity in the pathogenesis of MDS and BMF syndromes, including the paroxysmal nocturnal hemoglobinuria conundrum. Furthermore, we will briefly examine autoimmune complications following therapy of myeloid neoplasms, as well as the role of MSCs and microbiota in these settings.

Confounding factors in the diagnosis and clinical course of rare congenital hemolytic anemias

Congenital hemolytic anemias (CHAs) comprise defects of the erythrocyte membrane proteins and of red blood cell enzymes metabolism, along with alterations of erythropoiesis. These rare and heterogeneous conditions may generate several difficulties from the diagnostic point of view. Membrane defects include hereditary spherocytosis and elliptocytosis, and the group of hereditary stomatocytosis; glucose-6-phosphate dehydrogenase and pyruvate kinase, are the most common enzyme deficiencies. Among ultra-rare forms, it is worth reminding other enzyme defects (glucosephosphate isomerase, phosphofructokinase, adenylate kinase, triosephosphate isomerase, phosphoglycerate kinase, hexokinase, and pyrimidine 5′-nucleotidase), and congenital dyserythropoietic anemias. Family history, clinical findings (anemia, hemolysis, splenomegaly, gallstones, and iron overload), red cells morphology, and biochemical tests are well recognized diagnostic tools. Molecular findings are increasingly used, particularly in recessive and de novo cases, and may be fundamental in unraveling the diagnosis. Notably, several confounders may further challenge the diagnostic workup, including concomitant blood loss, nutrients deficiency, alterations of hemolytic markers due to other causes (alloimmunization, infectious agents, rare metabolic disorders), coexistence of other hemolytic disorders (autoimmune hemolytic anemia, paroxysmal nocturnal hemoglobinuria, etc.). Additional factors to be considered are the possible association with bone marrow, renal or hepatic diseases, other causes of iron overload (hereditary hemochromatosis, hemoglobinopathies, metabolic diseases), and the presence of extra-hematological signs/symptoms. In this review we provide some instructive clinical vignettes that highlight the difficulties and confounders encountered in the diagnosis and clinical management of CHAs.

Difficult Cases of Paroxysmal Nocturnal Hemoglobinuria: Diagnosis and Therapeutic Novelties

Paroxysmal nocturnal hemoglobinuria (PNH) is an intriguing disease that can pose many difficulties to physicians, as well as to hematologists, who are unfamiliar with it. Research regarding its pathophysiologic, diagnostic, and therapeutic aspects is still ongoing. In the last ten years, new flow cytometry techniques with high sensitivity enabled us to detect PNH clones as small as <1% of a patient's hematopoiesis, resulting in increasing incidence but more difficult data interpretation. Particularly, the clinical significance of small PNH clones in patients with bone marrow failures, including aplastic anemia and myelodysplastic syndromes, as well as in uncommon associations, such as myeloproliferative disorders, is still largely unknown. Besides current treatment with the anti-C5 eculizumab, which reduced PNH-related morbidity and mortality, new complement inhibitors will likely fulfill unmet clinical needs in terms of patients' quality of life and better response rates (i.e., responses in subjects with C5 polymorphisms; reduction of extravascular hemolysis and breakthrough hemolysis episodes). Still, unanswered questions remain for these agents regarding their use in mono- or combination therapy, when to treat, and which drug is the best for which patient. Lastly, long-term safety needs to be assessed in real-life studies. In this review, we describe some clinical vignettes illustrating practical aspects of PNH diagnosis and management; moreover, we discuss recent advances in PNH diagnostic and therapeutic approaches.

Autoimmune hemolytic anemia: current knowledge and perspectives

Autoimmune hemolytic anemia (AIHA) is an acquired, heterogeneous group of diseases which includes warm AIHA, cold agglutinin disease (CAD), mixed AIHA, paroxysmal cold hemoglobinuria and atypical AIHA. Currently CAD is defined as a chronic, clonal lymphoproliferative disorder, while the presence of cold agglutinins underlying other diseases is known as cold agglutinin syndrome. AIHA is mediated by autoantibodies directed against red blood cells (RBCs) causing premature erythrocyte destruction. The pathogenesis of AIHA is complex and still not fully understood. Recent studies indicate the involvement of T and B cell dysregulation, reduced CD4+ and CD25+ Tregs, increased clonal expansions of CD8 + T cells, imbalance of Th17/Tregs and Tfh/Tfr, and impaired lymphocyte apoptosis. Changes in some RBC membrane structures, under the influence of mechanical stimuli or oxidative stress, may promote autohemolysis. The clinical presentation and treatment of AIHA are influenced by many factors, including the type of AIHA, degree of hemolysis, underlying diseases, presence of concomitant comorbidities, bone marrow compensatory abilities and the presence of fibrosis and dyserthropoiesis. The main treatment for AIHA is based on the inhibition of autoantibody production by mono- or combination therapy using GKS and/or rituximab and, rarely, immunosuppressive drugs or immunomodulators. Reduction of erythrocyte destruction via splenectomy is currently the third line of treatment for warm AIHA. Supportive treatment including vitamin supplementation, recombinant erythropoietin, thrombosis prophylaxis and the prevention and treatment of infections is essential. New groups of drugs that inhibit immune responses at various levels are being developed intensively, including inhibition of antibody-mediated RBCs phagocytosis, inhibition of B cell and plasma cell frequency and activity, inhibition of IgG recycling, immunomodulation of T lymphocytes function, and complement cascade inhibition. Recent studies have brought about changes in classification and progress in understanding the pathogenesis and treatment of AIHA, although there are still many issues to be resolved, particularly concerning the impact of age-associated changes to immunity.