Detection of paroxysmal nocturnal hemoglobinuria clones in patients with myelodysplastic syndromes and related bone marrow diseases, with emphasis on diagnostic pitfalls and caveats

Monitoring and Treatment of Paroxysmal Nocturnal Hemoglobinuria in Patients with Aplastic Anemia in Asia: An Expert Consensus

Paroxysmal nocturnal hemoglobinuria (PNH) clones can be identified in a significant proportion of patients with aplastic anemia (AA). Screening for PNH clones at the time of an AA diagnosis is recommended by national and international guidelines. In this report, an expert panel of physicians discusses current best practices and provides recommendations for managing PNH in patients with AA in the Asia-Pacific region. Plasma/serum lactate dehydrogenase (LDH) levels and reticulocyte count should be measured with every blood test. PNH clone size should be monitored regularly by flow cytometry, with on-demand testing in the event of a rise in LDH level ± reticulocyte count or development of symptoms such as thrombosis. Monitoring for PNH clones can guide the choice of initial AA treatment, although flow cytometry has resource implications which may present a challenge in some Asia-Pacific countries. The treatment of patients with both PNH and AA depends on which condition predominates; following PNH treatment guidelines if hemolysis is the main symptom and AA treatment guidelines if bone marrow failure is severe (regardless of whether hemolysis is mild or moderate). The expert panel's recommendations on the monitoring and treatment of PNH in patients with AA are practical for healthcare systems in the Asia-Pacific region.

Management of paroxysmal nocturnal hemoglobinuria in CALR mutated post-essential thrombocythemia myelofibrosis: A case report

Paroxysmal nocturnal hemoglobinuria (PNH) results from the loss of erythrocyte surface proteins, leading to complement activation and its spectrum of effects. We explore this case of a 57-year-old man with post-essential thrombocythemia (ET) myelofibrosis (MF) who developed symptomatic anemia with evidence of hemolysis on lab work. While hemolysis was localized to be intramedullary based on workup, the exact diagnosis was undetermined, leading to a prolonged course of steroid therapy to control anemia. The hemolysis was eventually attributed to PNH diagnosed on flow cytometry and the patient was treated with complement inhibitors with eventual failure of therapy. He ultimately underwent a successful hematopoietic cell transplant (HCT) with post-transplantation flow cytometry showing complete resolution of PNH. While PNH has been identified as a progression of myelodysplastic syndromes, the mechanisms of its rare development in myeloproliferative neoplasms are poorly elucidated. Furthermore, its rarity and often vague symptoms make diagnosis and treatment a challenge. This is the second reported case of a JAK2-negative, CALR-positive post-ET MF and the first reported case to be treated with HCT. This case probes for further insight into the clinical significance between MF and PNH, its impact on management, and further consideration for HCT as curative therapy in such patients who fail complement inhibitor therapy.

Flow Cytometric Assessment of Myelodysplastic Syndromes/Neoplasms

Myelodysplastic syndromes/neoplasms (MDS) are a heterogeneous class of hematopoietic stem cell neoplasms characterized by ineffective hematopoiesis leading to peripheral cytopenias. This group of diseases is typically diagnosed using a combination of clinical, morphologic, and genetic criteria. Many studies have described the value of multiparametric flow cytometry (MFC) in the diagnosis, classification, and prognostication of MDS. This review summarizes the approach to MDS diagnosis and immunophenotypic characterization using MFC and describes the current state while highlighting future opportunities and potential pitfalls.

A longitudinal analysis of paroxysmal nocturnal haemoglobinuria-type cells in patients with bone marrow failure: Results of a prospective multi-centre study in Japan

To determine the prevalence and clinical relevance of glycosylphosphatidylinositol-anchored protein-deficient (GPI[-]) cell populations (paroxysmal nocturnal haemoglobinuria [PNH]-type cells) in patients with acquired aplastic anaemia (AA) or myelodysplastic syndrome (MDS), we prospectively studied peripheral blood samples of 2402 patients (1075 with AA, 900 with MDS, 144 with PNH, and 283 with other anaemia) using a high-sensitivity flow cytometry assay in a nationwide multi-centre observational study. PNH-type cells were detected in 52.6% of AA and 13.7% of MDS patients. None of the 35 patients with refractory anaemia (RA) with ringed sideroblasts or the 86 patients with RA with excess of blasts carried PNH-type cells. Among the 317 patients possessing PNH-type granulocytes, the percentage of PNH-type granulocytes increased by ≥10% in 47 patients (14.8%), remained unchanged in 240 patients (75.7%), and decreased by ≥10% in 30 patients (9.5%) during 3 years of follow-up. PNH-type granulocyte expansion occurred more frequently (27.1%) in the 144 patients who originally carried PNH-type granulocytes ≥1% than in the 173 patients with PNH-type granulocytes <1% (4.6%). This study confirmed that PNH-type cells are undetectable in authentic clonal MDS patients, and the presence of ≥1% PNH-type granulocytes predicts a higher likelihood of PNH-type cell expansion than with <1% PNH-type granulocytes.

Dysplasia and PNH-type cells in bone marrow aspirates of myelodysplastic syndromes

BACKGROUND

Flow cytometry is increasingly applied in cytopenic patients suspected for myelodysplastic syndromes (MDS). Analysis includes evaluation of antigen expression patterns in granulocytes of which, for example, partial lack of CD16 may indicate dysplasia, but presence of paroxysmal nocturnal hemoglobinuria (PNH)-type cells should be considered. However, diagnostic bone marrow (BM) samples hamper PNH analysis because immature stages in the granulo-/monocytic compartment lack expression of certain glycophosphatidyl-inositol-anchored proteins. In this prospective study, we evaluated the presence of PNH-type cells in BM next to aberrancies from routine MDS immunophenotyping.

METHODS

We combined antibodies defining maturation trajectories with FLAER. Validation of the designed method against routine PNH analysis and parallel analysis of BM and blood samples revealed similar results (granulocytes: Wilcoxon p = 0.25 and p = 0.82, respectively). We analyzed BM samples from 134 MDS, 17 chronic myelomonocytic leukemia, 15 aplastic anemia (AA), 1 PNH, 51 non-clonal cytopenic controls, and 12 normal controls.

RESULTS

Most AA/PNH-BM samples showed clear PNH clones: median 1.1% (0%-35%); CD16 loss on mature neutrophils paralleled PNH-clone sizes. In MDS-BM, only 3.7% of cases showed ≥0.1% PNH-type cells, whereas partial CD16 loss was more frequent and abundant.

CONCLUSIONS

Our findings confirm that dysplastic features in MDS-BM may point to presence of PNH-type cells, though only few cases displayed FLAER-negative cells. We showed that identification of these cells in the granulocyte compartment of BM specimen is feasible, but-according to international guidelines-results need to be confirmed in peripheral blood.

Myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are a family of myeloid cancers with diverse genotypes and phenotypes characterized by ineffective haematopoiesis and risk of transformation to acute myeloid leukaemia (AML). Some epidemiological data indicate that MDS incidence is increasing in resource-rich regions but this is controversial. Most MDS cases are caused by randomly acquired somatic mutations. In some patients, the phenotype and/or genotype of MDS overlaps with that of bone marrow failure disorders such as aplastic anaemia, paroxysmal nocturnal haemoglobinuria (PNH) and AML. Prognostic systems, such as the revised International Prognostic Scoring System (IPSS-R), provide reasonably accurate predictions of survival at the population level. Therapeutic goals in individuals with lower-risk MDS include improving quality of life and minimizing erythrocyte and platelet transfusions. Therapeutic goals in people with higher-risk MDS include decreasing the risk of AML transformation and prolonging survival. Haematopoietic cell transplantation (HCT) can cure MDS, yet fewer than 10% of affected individuals receive this treatment. However, how, when and in which patients with HCT for MDS should be performed remains controversial, with some studies suggesting HCT is preferred in some individuals with higher-risk MDS. Advances in the understanding of MDS biology offer the prospect of new therapeutic approaches.

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.

A Prospective, Cross Sectional Study of PNH Clone in MDS Patients Using High Sensitivity Flowcytometry: A Single Center Experience

Subclinical PNH can be present in patients with bone marrow failure like aplastic anemia and myelodysplastic syndrome (MDS). Such clone may have prognostic and therapeutic implications. In literature around 1-10% MDS cases have shown a PNH clone, however, data from India is relatively scarce. A high sensitivity PNH assay was employed using a single tube combination of FLAER, CD157, CD64, CD15 and CD45 antibodies in adult patients of MDS at presentation. A clone size of  > 0.01% was taken as significant. A total of 30 patients were included. PNH clone was present in 30% cases. Correlation done between PNH clone size and LDH values showed moderately positive correlation (r = 0.735, p = 0.001, r2 = 0.541). As per this study a LDH cut off of 247 IU is likely to predict a PNH clone (> 1%) with moderate sensitivity and specificity. High sensitivity PNH assay is able to detect small PNH clone. Calculating the cut-off of LDH to predict PNH positivity can help us judiciously prescribe this test in MDS patients in resource constrained settings.

Laboratory studies for paroxysmal nocturnal hemoglobinuria, with emphasis on flow cytometry

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare acquired clonal hematopoietic stem cell disorder caused by somatic mutations in the PIG-A gene, leading to the production of blood cells with absent or decreased expression of glycosylphosphatidylinositol-anchored proteins, including CD55 and CD59. Clinically, PNH is classified into three variants: classic (hemolytic), in the setting of another specified bone marrow disorder (such as aplastic anemia or myelodysplastic syndrome) and subclinical (asymptomatic). PNH testing is recommended for patients with intravascular hemolysis, acquired bone marrow failure syndromes and thrombosis with unusual features. Despite the availability of consensus guidelines for PNH diagnosis and monitoring, there are still discrepancies on how PNH tests are carried out, and these technical variations may lead to an incorrect diagnosis. Herein, we provide a brief historical overview of PNH, focusing on the laboratory tests available and on the current recommendations for PNH diagnosis and monitoring based in flow cytometry.

Flow Cytometric Diagnosis of Paroxysmal Nocturnal Hemoglobinuria: Pearls and Pitfalls - A Critical Review Article

Paroxysmal Nocturnal Hemoglobinuria (PNH) is a rare blood disorder characterized by chronic intravascular hemolysis, thromboses in unusual sites and cytopenias related to bone marrow failure. The diagnosis is based on the Flow Cytometric (FCM) detection of peripheral blood cell clones lacking the surface molecules linked to the GPI anchor, which is altered by mutations. Consensus studies have developed standardized and robust multicolor FCM assays to disclose PNH clones among red cells, neutrophils and monocytes at a high level of sensitivity and accuracy. High-resolution procedures have been also established to detect small PNH clones at a sensitivity level of around 0.01% in red cells and neutrophils. Cell clone type and size have been put into correlation with the clinical presentations of the associated diseases, and recommendations for the clinical follow-up have been established. The recent advent of the therapeutic monoclonal antibody Eculizumab has dramatically improved both the quality of life and the life expectancy of the affected patients, further increasing the importance of an accurate FCM detection and monitoring of the clones. The technical features of the FCM diagnostic workup and the many critical aspects of the analytical process are discussed here.

FLAER Based Assay According to Newer Guidelines Increases Sensitivity of PNH Clone Detection

Flow cytometry has become 'gold standard' for detecting abnormal clones in paroxysmal nocturnal hemoglobinuria (PNH), aplastic anemia (AA) and myelodysplastic syndrome (MDS). This pilot study was conducted in 2015 with a primary aim to evaluate the utility of single tube fluorescent aerolysin (FLAER) based testing and its comparison with two tubes non-FLAER based testing (CD55, CD59, CD24 and CD66b) in detecting abnormal PNH clones in these newly diagnosed cases. The secondary aim was an attempt to distinguish PNH from AA/MDS cases associated with PNH clones based on clinical, laboratory features and clone size at diagnosis. In this study, the abnormal PNH clones were detected using a single tube FLAER based testing and two tubes non-FLAER based testing in all cases of PNH (n = 12), healthy subjects (n = 18) and AA/MDS with PNH clone (n = 9) and compared with clinical and laboratory features at diagnosis. The receiver operator curve (ROC) analysis defined the optimal cut-offs for FLAER in granulocytes (> 0.7%) and monocytes (> 0.9%). There was significant positive correlation between FLAER and non-FLAER based testing in these cells (r > 0.3 and p < 0.05). FLAER based testing helped us in picking up smaller clones which were missed by latter technique in four patients thereby increasing its sensitivity and also technically proved to be cost-effective (Rs. 1800 vs. Rs. 2100). Even in PNH patients, the clone size was slightly higher by using FLAER when compared to non-FLAER based antibodies panel. The clone size of monocytes was always higher than granulocytes in both PNH and AA/MDS groups. Bone marrow cellularity and mean size of granulocytes and monocytes clone at diagnosis showed a striking statistically significant 'p' value of < 0.0001 between these groups. In this pilot study, a single tube FLAER based PNH testing had improved clone detection in all cases of PNH, AA/MDS with PNH clones. The clone size was > 30% in majority of PNH cases whereas in AA/MDS, it was usually < 10% at diagnosis. Hence this newer technique not only increased the sensitivity of PNH clone detection but also proved to be cost-effective.

Evolution patterns of paroxysmal nocturnal hemoglobinuria clone and clinical implications in acquired bone marrow failure

The paroxysmal nocturnal hemoglobinuria (PNH) clone often presents in acquired bone marrow failure (aBMF), which is involved in more than half of aplastic anemia (AA) cases and about 10%-20% of myelodysplastic syndrome (MDS) cases. PNH clone expansion patterns and clinical implications, however, remain obscure. We conducted a large retrospective study of 457 aBMF patients with positive PNH clones to explore the wide spectrum of clone architecture, evolution patterns, and clinical implications. PNH clone size at diagnosis in AA or MDS was significantly smaller than that in clinical PNH (p < 0.001); the main clone patterns in AA and MDS were granulocyte dominant, with the remaining cases having a granulocyte-erythrocyte balance pattern in clinical PNH. In 131 AA patients at follow-up, there was no obvious difference in response rates between those with the aggressive pattern of clone evolution (73.7%) and those with the stable pattern (81.1%). A quarter of AA patients evolved into clinical hemolysis within a median interval of 11 months. AA cases progressing into clinical hemolysis after immunosuppressive therapy had significantly larger clones (granulocytes: 12.3% vs. 2.6%; erythrocytes: 5.7% vs. 1.3%) at diagnosis and presented mainly an aggressive pattern, especially the granulocyte-erythrocyte aggressive model. Clone sizes reaching 37% for erythrocytes and 28% for granulocytes were indicators of the onset of hemolysis in AA. In conclusion, aBMF patients presented significantly various PNH clone patterns at diagnosis. AA patients with either an aggressive or stable evolution pattern can achieve a response, but patients with an aggressive evolution pattern, especially the granulocyte-erythrocyte aggressive model, tend to evolve into clinical hemolysis.

Paroxysmal nocturnal hemoglobinuria testing in patients with myelodysplastic syndrome in clinical practice-frequency and indications

Background

Myelodysplastic syndrome (mds) is characterized by peripheral blood cytopenias, with most patients developing significant anemia and dependence on red blood cell (rbc) transfusion. In paroxysmal nocturnal hemoglobinuria (pnh), mutations in the PIGA gene lead to lack of cell-surface glycosylphosphatidylinositol, allowing complement-mediated lysis to occur. Paroxysmal nocturnal hemoglobinuria results in direct antiglobulin test-negative hemolysis and cytopenias, and up to 50% of patients with mds test positive for pnh cells. We wanted to determine whether pnh is considered to be a contributor to anemia in mds.

Methods

Patients with a diagnosis of mds confirmed by bone-marrow biopsy since 2009 were reviewed. High-resolution pnh testing by flow cytometry examined flaer (fluorescein-labeled proaerolysin) binding and expression of CD14, CD15, CD24, CD45, CD59, CD64, and CD235 on neutrophils, monocytes, and rbcs.

Results

In 152 patients with mds diagnosed in 2009 or later, the mds diagnosis included subtypes associated with pnh positivity (refractory anemia, n = 7, and hypoplastic mds, n = 4). Of 11 patients who underwent pnh testing, 1 was positive (9.0%). Reasons for pnh testing were anemia (n = 3), new mds diagnosis (n = 2), hypoplastic mds (n = 2), decreased haptoglobin (n= 1), increased rbc transfusion requirement (n= 1), and unexplained iron deficiency (n= 1).

Conclusions

Testing for pnh was infrequent in mds patients, and the criteria for testing were heterogeneous. Clinical indicators prompted pnh testing in 6 of 11 patients. Given that effective treatment is now available for pnh and that patients with pnh-positive mds can respond to immunosuppressive therapy, pnh testing in mds should be considered. Prospective analyses to clarify the clinical significance of pnh positivity in mds are warranted.

Establishment of a flow cytometry assay for detecting paroxysmal nocturnal hemoglobinuria-type cells specific to patients with bone marrow failure

Minor populations of glycosylphosphatidylinositol-anchored protein-deficient (GPI[-]) cells in the peripheral blood may have a prognostic value in bone marrow failure (BMF). Our objective is to establish the optimal flow cytometry (FCM) assay that can discriminate GPI(-) populations specific to BMF from those of healthy individuals. To identify a cut-off that discriminates GPI(-) rare cells from GPI(+) cells, we determined a position of the borderline that separates the GPI(-) from GPI(+) cells on a scattergram by testing more than 30 healthy individuals, such that no GPI(-) dot fell into the upper left quadrant where fluorescein-labeled aerolysin (FLAER)^-CD11b⁺ granulocytes and CD55^-CD59^- glycophorin A⁺ erythrocytes were positioned. This method allowed us to define ≥ 0.003% CD11b⁺FLAER^- granulocytes and ≥ 0.005% glycophorin A⁺CD55^-CD59^- erythrocytes to be specific to BMF patients. Longitudinal cross-validation studies showed minimal (< 0.02%) inter-laboratory differences in the GPI(-) cell percentage. An analysis of 1210 patients with BMF revealed a GPI(-) cell population in 56.3% of patients with aplastic anemia and 18.5% of patients with myelodysplastic syndrome. The GPI(-) granulocyte percentages was 0.003-0.01% in 3.7% of patients. This FCM assay effectively identified an increase in the percentage of GPI(-) rare cells that are specific to BMF patients and allowed different laboratories to accurately detect 0.003-0.01% of pathological GPI(-) cells.

Diagnostic algorithm for lower-risk myelodysplastic syndromes

Rapid advances over the past decade have uncovered the heterogeneous genomic and immunologic landscape of myelodysplastic syndromes (MDS). This has led to notable improvements in the accuracy and timing of diagnosis and prognostication of MDS, as well as the identification of possible novel targets for therapeutic intervention. For the practicing clinician, however, this increase in genomic, epigenomic, and immunologic knowledge needs consideration in a "real-world" context to aid diagnostic specificity. Although the 2016 revision to the World Health Organization classification for MDS is comprehensive and timely, certain limitations still exist for day-to-day clinical practice. In this review, we describe an up-to-date diagnostic approach to patients with suspected lower-risk MDS, including hypoplastic MDS, and demonstrate the requirement for an "integrated" diagnostic approach. Moreover, in the era of rapid access to massive parallel sequencing platforms for mutational screening, we suggest which patients should undergo such analyses, when such screening should be performed, and how those data should be interpreted. This is particularly relevant given the recent findings describing age-related clonal hematopoiesis.

Value of CD16/CD66b/CD45 in comparison to CD55/CD59/CD45 in diagnosis of paroxysmal nocturnal haemoglobinuria: An Indian experience

Background & objectives:

Diagnosis of paroxysmal nocturnal haemoglobinuria (PNH), a rare haematopoietic stem cell disorder, is challenging in patients with bone marrow failure (BMF) syndrome like aplastic anaemia (AA). This study was conducted with the aim to test the efficacy of the newly recommended markers viz. anti-CD16 and CD66b antibody over the existing anti-CD55 and CD59 antibody for PNH diagnosis in India.

Methods:

This study was conducted on 193 suspected cases of PNH by flow cytometry using lyse wash technique to stain the granulocytes with CD16/CD66b and CD55/CD59.

Results:

Of the 193 suspected cases, 62 patients showed the presence of PNH clone. Forty six patients were detected by CD55/CD59/CD45, whereas 61 were detected by CD16/CD66b/CD45. CD16/CD66b detected 16 (25.8%) additional patients over CD55/CD59 (P<0.05) and was more sensitive in detecting the PNH clone with higher negative predictive value. Most of the patients (11/16) who were picked up by CD16/CD66b were of AA who had small clone sizes. Further, the PNH clones were more discreetly identified in CD16/CD66b plots than by CD55/CD59. Clone size assessed by CD16/CD66b which reflects the clinical severity of classical PNH (thrombosis/haemolysis), was more representative of the underlying clinical condition than CD55/59.

Interpretation & conclusions:

In our experience of 62 patients of PNH, CD16/CD66b proved to be more efficacious in detecting PNH. The new panel was especially useful in monitoring PNH associated with BMF which had small clone sizes.

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.

Recent advances in understanding clonal haematopoiesis in aplastic anaemia

Acquired aplastic anaemia (AA) is an immune-mediated bone marrow failure disorder inextricably linked to clonal haematopoiesis. The majority of AA patients have somatic mutations and/or structural chromosomal abnormalities detected as early as at diagnosis. In contrast to other conditions linked to clonal haematopoiesis, the clonal signature of AA reflects its immune pathophysiology. The most common alterations are clonal expansions of cells lacking glycophosphotidylinositol-anchored proteins, loss of human leucocyte antigen alleles, and mutations in BCOR/BCORL1, ASXL1 and DNMT3A. Here, we present the current knowledge of clonal haematopoiesis in AA as it relates to aging, inherited bone marrow failure, and the grey-zone overlap of AA and myelodysplastic syndrome (MDS). We conclude by discussing the significance of clonal haematopoiesis both for improved diagnosis of AA, as well as for a more precise, personalized approach to prognostication of outcomes and therapy choices.

Update on the diagnosis and management of paroxysmal nocturnal hemoglobinuria

Once suspected, the diagnosis of paroxysmal nocturnal hemoglobinuria (PNH) is straightforward when flow cytometric analysis of the peripheral blood reveals a population of glycosyl phosphatidylinositol anchor protein-deficient cells. But PNH is clinically heterogeneous, with some patients having a disease process characterized by florid intravascular, complement-mediated hemolysis, whereas in others, bone marrow failure dominates the clinical picture with modest or even no evidence of hemolysis observed. The clinical heterogeneity is due to the close, though incompletely understood, relationship between PNH and immune-mediated bone marrow failure, and that PNH is an acquired, nonmalignant clonal disease of the hematopoietic stem cells. Bone marrow failure complicates management of PNH because compromised erythropoiesis contributes, to a greater or lesser degree, to the anemia; in addition, the extent to which the mutant stem cell clone expands in an individual patient determines the magnitude of the hemolytic component of the disease. An understanding of the unique pathobiology of PNH in relationship both to complement physiology and immune-mediated bone marrow failure provides the basis for a systematic approach to management.

Diagnostic screening of paroxysmal nocturnal hemoglobinuria: Prospective multicentric evaluation of the current medical indications

BACKGROUND

Although consensus guidelines have been proposed in 2010 for the diagnostic screening of paroxysmal nocturnal hemoglobinuria (PNH) by flow cytometry (FCM), so far no study has investigated the efficiency of such medical indications in multicentric vs. reference laboratory settings.

METHODS

Here we evaluate the efficiency of consensus medical indications for PNH testing in 3,938 peripheral blood samples submitted to FCM testing in 24 laboratories in Spain and one reference center in Brazil.

RESULTS

Overall, diagnostic screening based on consensus medical indications was highly efficient (14% of PNH⁺ samples) both in the multicenter setting in Spain (10%) and the reference laboratory in Brazil (16%). The highest frequency of PNH⁺ cases was observed among patients screened because of bone marrow (BM) failure syndrome (33%), particularly among those with aplastic anemia (AA; 45%) and to a less extent also a myelodysplastic syndrome (MDS; 10%). Among the other individuals studied, the most efficient medical indications for PNH screening included: hemolytic anemia (19%), hemoglobinuria (48%) and unexplained cytopenias (9%). In contrast, only a minor fraction of the patients who had been submitted for PNH testing because of unexplained thrombosis in the absence of cytopenia, were positive (0.4%).

CONCLUSIONS

In summary, our results demonstrate that the current medical indications for PNH screening by FCM are highly efficient, although improved screening algorithms are needed for patients presenting with thrombosis and normal blood cell counts. © 2016 International Clinical Cytometry Society.

Minor populations of paroxysmal nocturnal hemoglobinuria-type cells in patients with chronic idiopathic neutropenia

Chronic idiopathic neutropenia (CIN) is an acquired disorder of granulopoiesis characterized by increased apoptosis of the bone marrow (BM) granulocytic progenitor cells under the influence of pro-inflammatory mediators and oligoclonal/monoclonal T-lymphocytes. Because patients with immune-mediated BM failure display frequently paroxysmal nocturnal hemoglobinuria (PNH)-type cells in the peripheral blood (PB), we investigated the possible existence of PNH-type cells in 91 patients with CIN using flow cytometry. The patients displayed increased proportions of PNH-type glycophorin A⁺ /CD59^dim and glycophorin A⁺ /CD59^- red blood cells (RBCs), FLAER^- /CD24^- granulocytes, and FLAER^- /CD14^- monocytes, compared to controls (n = 55). A positive correlation was found between the proportions of PNH-type RBCs, granulocytes, and monocytes and an inverse correlation between the number of PB neutrophils and the proportions of PNH-type cell populations. The number of patients, displaying percentages of PNH-type cells above the highest percentage observed in the control group, was significantly increased among patients with skewed compared to those with normal T-cell receptor repertoire suggesting that T-cell-mediated immune processes underlie the emergence of PNH-type cells in CIN. Our findings suggest that patients with CIN display PNH-type cells in the PB at a high frequency corroborating the hypothesis that CIN belongs to the immune-mediated BM failure syndromes.

[Clinical and laboratory characteristics in patients of myelodysplastic syndrome with PNH clones]

OBJECTIVE

To analyze the clinical, laboratory characteristics and PIG-A gene mutations in patients of myelodysplastic syndromes (MDS) with PNH clones.

METHODS

218 MDS patients diagnosed from August 2013 to August 2015 were analyzed. The PIG-A gene mutations were tested in 13 cases of MDS with PNH clones, 17 cases of AA-PNH and 14 cases of PNH selected contemporaneously by PCR and direct sequencing.

RESULTS

13 (5.96%) MDS patients were detected with PNH clones (13/218 cases). 9 patients were treated with cyclosporin A (CsA). Patients showed hematological improvement (HI). There were significant differences between MDS-PNH and PNH patients in terms of granulocyte clone size, red cell clone size and LDH levels [19.2% (1.0%-97.7%) vs 60.2% (3.1%-98.0%), P=0.007; 4.3% (0-67.2%) vs 27.9% (2.5%-83.6%), P=0.026; 246 (89-2014) U/L vs 1137 (195-2239) U/L, P=0.049], while the differences were not statistically significant in patients between MDS-PNH and AA-PNH patients [19.2% (1.0%-97.7%) vs 23.2% (1.5%-96.0%), P=0.843; 4.3% (0-67.2%) vs 14.4% (1.1%-62.8%), P=0.079; 246 (89-2014) U/L vs 406 (192-1148) U/L, P=0.107]. PIG-A gene mutations were detected in 7 MDS-PNH patients, of them, six were missense mutations, one were frameshift mutation and four cases with the same mutation of c.356G>A (R119Q). The PIG-A gene mutations were also detected in 9/11 AA-PNH patients and 11/14 PNH patients, both of them had the mutation of c.356G>A (R119Q). The PIG-A gene mutations of MDS-PNH, AA-PNH, PNH patients were all small mutations, the majority of those (59%) were missense mutation and mainly located in exon 2.

CONCLUSION

MDS patients with PNH clones had better response to CsA, smaller PNH clone size. The PIG-A gene mutations of MDS-PNH patients mainly located in exon 2, which could be a mutational hotspot of these patients.

Combination of CD157 and FLAER to Detect Peripheral Blood Eosinophils by Multiparameter Flow Cytometry

The identification of eosinophils by flow cytometry is difficult because most of the surface antigens expressed by eosinophils are shared with neutrophils. Some methods have been proposed, generally based on differential light scatter properties, enhanced autofluorescence, lack of CD16 or selective positivity of CD52. Such methods, however, show several limitations. In the present study we report a novel method based on the analysis of glycosylphosphatidylinositol (GPI)-linked molecules. The combination of CD157 and FLAER was used, since FLAER recognizes all GPI-linked molecules, while CD157 is absent on the membrane of eosinophils and expressed by neutrophils. Peripheral blood samples from normal subjects and patients with variable percentages of eosinophils (n = 31), and without any evidence for circulating immature myeloid cells, were stained with the combination of FLAER-Alexa Fluor and CD157-PE. A FascCanto II cytometer was used. Granulocytes were gated after CD33 staining and eosinophils were identified as CD157(-)/FLAER(+) events. Neutrophils were identified as CD157(+)/FLAER(+) events. The percentages of eosinophils detected by this method showed a very significant correlation both with automated counting and with manual counting (r = 0.981 and 0.989, respectively). Sorting assays were carried out by a S3 Cell Sorter: cytospins obtained from CD157(-)/FLAER(+) events consisted of 100% eosinophils, while samples from CD157(+)/FLAER(+) events were represented only by neutrophils. In conclusion, this method shows high sensitivity and specificity in order to distinguish eosinophils from neutrophils by flow cytometry. However, since CD157 is gradually up-regulated throughout bone marrow myeloid maturation, our method cannot be applied to cases characterized by immature myeloid cells.

Significance of the detection of paroxysmal nocturnal hemoglobinuria clones in patients with multiple myeloma undergoing autologous stem cell transplantation

OBJECTIVE/BACKGROUND

There are reports about the presence of paroxysmal nocturnal hemoglobinuria (PNH) clones in multiple myeloma (MM), but these have been demonstrated only in red blood cells (RBCs) and the previous reports utilized an obsolete diagnostic method. We carried out a study to identify the clones by flow cytometry (FC) and to understand their clinical significance.

METHODS

A prospective study on consecutive patients with newly diagnosed MM who were candidates for autologous stem cell transplantation (ASCT) from 2008 to 2012. We screened peripheral blood samples by FC for CD55- and/or CD59-deficient RBC, neutrophils, and monocytes. PNH testing was carried out at diagnosis, before ASCT and 3 months after ASCT, as well as sporadically during MM remission and at disease relapse.

RESULTS

A total of 31 patients were included in the study. PNH clones reaching a median size of 10.8% (range 4.0-18.7%) were found in 10 patients (32.3%). Clones were detected at diagnosis in nine patients and 3 months after ASCT in one patient. A correlation between the presence of the clones and subclinical hemolysis was observed. Nevertheless, the presence of the clones did not influence the overall management and prognosis of the patients.

CONCLUSION

We confirmed findings of previous reports with current diagnostic guidelines and showed that although the size of the clones may be relatively large, their presence is probably not detrimental. The clinical significance of these clones and the possible mechanisms underlying their expansion in MM must be a subject of further investigation.

Pathophysiology, diagnosis, and treatment of paroxysmal nocturnal hemoglobinuria: a review

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.

Increased glycosylphosphatidylinositol-anchored protein-deficient granulocytes define a benign subset of bone marrow failures in patients with trisomy 8

Trisomy 8 (+8), one of the most common chromosomal abnormalities found in patients with myelodysplastic syndromes (MDS), is occasionally seen in patients with otherwise typical aplastic anemia (AA). Although some studies have indicated that the presence of +8 is associated with the immune pathophysiology of bone marrow (BM) failure, its pathophysiology may be heterogeneous. We studied 53 patients (22 with AA and 31 with low-risk MDS) with +8 for the presence of increased glycosylphosphatidylinositol-anchored protein-deficient (GPI-AP(-) ) cells, their response to immunosuppressive therapy (IST), and their prognosis. A significant increase in the percentage of GPI-AP(-) cells was found in 14 (26%) of the 53 patients. Of the 26 patients who received IST, including nine with increased GPI-AP(-) cells and 17 without increased GPI-AP(-) cells, 14 (88% with increased GPI-AP(-) cells and 41% without increased GPI-AP(-) cells) improved. The overall and event-free survival rates of the +8 patients with and without increased GPI-AP(-) cells at 5 yr were 100% and 100% and 59% and 57%, respectively. Examining the peripheral blood for the presence of increased GPI-AP(-) cells may thus be helpful for choosing the optimal treatment for +8 patients with AA or low-risk MDS.

Analysis of abnormal clones by the fluorescent aerolysin method in paroxysmal nocturnal haemoglobinuria and other marrow disorders

INTRODUCTION

Flow cytometry is the most sensitive and specific diagnostic modality for the assessment of clone size in paroxysmal nocturnal haemoglobinuria (PNH) and other bone marrow failure states. In this study, we attempt to distinguish PNH from aplastic anaemia (AA) and myelodysplastic syndromes (MDS) associated with PNH clones at diagnosis by clone size, clinical and laboratory features.

METHODS

A total of 29 samples included 19 PNH cases and 10 AA/MDS cases with PNH clones. Flow cytometry was performed using fluorescent aerolysin (FLAER)-based assay and comparison of clinical features, laboratory parameters and PNH clone size was carried out at diagnosis.

RESULTS

The PNH clone size on granulocytes varied from 0.4% to 99.2% and correlated with the clone size on monocytes (r = 0.966; P < 0.001). Paroxysmal nocturnal haemoglobinuria clone size on granulocytes (median = 34.6%) and monocytes (median = 49.9%) was always larger than erythrocytes (median = 10.9%). The median clone size in PNH (median granulocytes = 74.9%, monocytes = 71.8%) was significantly greater than in AA/MDS associated with PNH clone (median granulocytes = 2.9%, monocytes = 6%). In PNH patients, a significant negative correlation was seen between PNH clone on monocytes and the haemoglobin concentration.

CONCLUSION

In our small study using the FLAER method, the clone size was >70% in majority of PNH cases. In other marrow disorders like AA/MDS, the clone size was usually <10%.

Diagnosis of paroxysmal nocturnal hemoglobinuria in peripheral blood and bone marrow with six-color flow cytometry

AIM

Identification of paroxysmal nocturnal hemoglobinuria (PNH) by detecting a glycophosphatidylinositol-anchored defect by flow cytometry is presently the standard method of choice for diagnosing PNH. However, the selection of suitable markers will be critical and significantly affect the determination and quantification of PNH clones in various cell lineages.

MATERIALS & METHODS

In this study, we investigated the performance of various immunophenotypic markers including CD59, GPHA (a clustered antigen, CD235a), CD33, CD15 and fluorescent aerolysin (FLAER) combined with CD16, CD24 and CD14 in a PNH panel using six-color flow cytometry.

RESULTS

The results strongly indicate that these markers can collectively and effectively identify and quantify PNH clones in erythrocyte, granulocyte and monocyte populations derived from peripheral blood and bone marrow (BM). A sensitivity threshold as low as 0.01% in identifying PNH clones in erythrocyte and granulocyte populations from peripheral blood is achieved by this panel in a series dilution assay. In addition, a direct side-by-side comparison between BM and peripheral blood from the same patients suggests that the FLAER PNH test is capable of identifying to PNH clones in BM specimens.

CONCLUSION

The data support the premise that a six-color flow cytometry PNH panel using the combination of CD59, CD235a, CD33, CD15, FLAER, CD16, CD24 and CD14 can enhance and improve the current methods used in diagnosis and management of PNH by specifically identifying PNH clones in the erythrocyte, granulocyte and monocyte population.

Hemoglobinuria misidentified as hematuria: review of discolored urine and paroxysmal nocturnal hemoglobinuria

Discolored urine is a common reason for office visits to a primary care physician and urology referral. Early differentiation of the type or cause of discolored urine is necessary for accurate diagnosis and prompt management.

Paroxysmal nocturnal hemoglobinuria is a clonal disorder caused by acquired somatic mutations in the PIG-A gene on the X- chromosome of hemopoietic stem cells and leads to deficiency of surface membrane anchor proteins. The deficiency of these proteins leads to an increased risk of hemolysis of erythrocytes and structural damage of platelets, resulting in a clinical syndrome characterized by complement-mediated intravascular hemolytic anemia, bone marrow failure, and venous thrombosis. Patients with this clinical syndrome present with paroxysms of hemolysis, causing hemoglobinuria manifesting as discolored urine. This can be easily confused with other common causes of discolored urine and result in extensive urologic work-up. Three commonly confused entities of discolored urine include hematuria, hemoglobinuria, and myoglobinuria. Specific characteristics in a dipstick test or urinalysis can guide differentiation of these three causes of discolored urine.

This article begins with a case summary of a woman presenting with cranberry-colored urine and a final delayed diagnosis of paryxysmal nocturnal hemoglobinuria. Her hemoglobinuria was misdiagnosed as hematuria, leading to extensive urologic work-up. The article also gives an overview of the approach to diagnosing and treating discolored urine.

What's all the fuss about? facts and figures about bone marrow failure and conditions

The epidemiology of bone marrow failure conditions is not well understood. Although several population-based studies conducted in the last two decades have generated a wealth of information, it is still very challenging to interpret disease incidence and prevalence, particularly due to changes in disease classification, misdiagnosis of patients, frequent underreporting and use of different referent populations to calculate rates. Despite these limitations, the available epidemiologic data have revealed significant ethnic, geographic and clinical differences in disease biology that have implications for prevention and treatment strategies. With advances made in targeted therapies facilitated by identification of molecular biomarkers and increased use of curative bone marrow transplantation approach, the natural history of these disease entities is already changing. The epidemiology of these diseases seems to be the next frontier as knowledge gained about the risk factors and pathobiologic correlates could significantly help in designing patient-specific therapies with improved outcomes.

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).

A systematic analysis of bone marrow cells by flow cytometry defines a specific phenotypic profile beyond GPI deficiency in paroxysmal nocturnal hemoglobinuria

BACKGROUND

Paroxysmal nocturnal hemoglobinuria (PNH) is a unique disorder caused by a PIG-A gene mutation in a stem cell clone. Its clinical picture can sometimes make challenging the distinction from other disorders, and especially from myelodysplastic syndromes (MDS), since both diseases correlate with cytopenias and morphological abnormalities of bone marrow (BM) cells. Recently, flow cytometry (FC) has been proposed to integrate the morphologic assessment of BM dysplasia, and thus to improve the diagnostics of MDS.

METHODS

In the present study, we have analyzed systematically FC data resulting from the study of BM cells from patients with PNH and MDS.

RESULTS

Our data demonstrated abnormalities in PNH beyond the deficiency of glycosylphosphatidylinositol-linked proteins and the application of a systematic approach allowed us to separate effectively MDS and PNH in a cluster analysis and to highlight disease-specific abnormalities. Indeed, the parallel evaluation of some key parameters, i.e. patterns of expression of CD45 and CD10, provided information with practical diagnostic usefulness in the distinction between PNH and MDS. Moreover, the hypo-expression of CD36 that we observed on monocytes might be related to the thrombotic tendency in PNH.

CONCLUSIONS

We investigated systematically the phenotypic profile of BM cells from patients with PNH; our data provide useful antigenic patterns to solve between PNH and MDS, sometimes morphologically overlapping. Moreover, some PNH-related phenotypic changes might be involved in the physiopathology of the disease and further studies addressing this issue are warranted.

Diagnosis of myelodysplastic syndromes in cytopenic patients

Sustained clinical cytopenia is a frequent laboratory finding in ambulatory and hospitalized patients. For pathologists and hematopathologists who examine the bone marrow (BM), a diagnosis of cytopenia secondary to an infiltrative BM process or acute leukemia can be readily established based on morphologic evaluation and flow cytometry immunophenotyping. However, it can be more challenging to establish a diagnosis of myelodysplastic syndrome (MDS). In this article, the practical approaches for establishing or excluding a diagnosis of MDS (especially low-grade MDS) in patients with clinical cytopenia are discussed along with the current diagnostic recommendations provided by the World Health Organization and the International Working Group for MDS.

The small population of PIG-A mutant cells in myelodysplastic syndromes do not arise from multipotent hematopoietic stem cells

BACKGROUND

Patients with paroxysmal nocturnal hemoglobinuria harbor clonal glycosylphosphatidylinositol-anchor deficient cells arising from a multipotent hematopoietic stem cell acquiring a PIG-A mutation. Many patients with aplastic anemia and myelodysplastic syndromes also harbor small populations of glycosylphosphatidylinositol-anchor deficient cells. Patients with aplastic anemia often evolve into paroxysmal nocturnal hemoglobinuria; however, myelodysplastic syndromes seldom evolve into paroxysmal nocturnal hemoglobinuria. Here, we investigate the origin and clonality of small glycosylphosphatidylinositol-anchor deficient cell populations in aplastic anemia and myelodysplastic syndromes.

DESIGN AND METHODS

We used peripheral blood flow cytometry to identify glycosylphosphatidylinositol-anchor deficient blood cells, a proaerolysin-resistant colony forming cell assay to select glycosylphosphatidylinositol-anchor deficient progenitor cells, a novel T-lymphocyte enrichment culture assay with proaerolysin selection to expand glycosylphosphatidylinositol-anchor deficient T lymphocytes, and PIG-A gene sequencing assays to identify and analyze PIG-A mutations in patients with aplastic anemia and myelodysplastic syndromes.

RESULTS

Twelve of 15 aplastic anemia patients were found to harbor a small population of glycosylphosphatidylinositol-anchor deficient granulocytes; 11 of them were found to harbor a small population of glycosylphosphatidylinositol-anchor deficient erythrocytes, 10 patients were detected to harbor glycosylphosphatidylinositol-anchor deficient T lymphocytes, and 3 of them were detected only after T-lymphocyte enrichment in proaerolysin selection. PIG-A mutation analyses on 3 patients showed that all of them harbored a matching PIG-A mutation between CFU-GM and enriched T lymphocytes. Two of 26 myelodysplastic syndromes were found to harbor small populations of glycosylphosphatidylinositol-anchor deficient granulocytes and erythrocytes transiently. Bone marrow derived CD34(+) cells from 4 patients grew proaerolysin-resistant colony forming cells bearing PIG-A mutations. No glycosylphosphatidylinositol-anchor deficient T lymphocytes were detected in myelodysplastic syndrome patients.

CONCLUSIONS

In contrast to aplastic anemia and paroxysmal nocturnal hemoglobinuria, where PIG-A mutations arise from multipotent hematopoietic stem cells, glycosylphosphatidylinositol-anchor deficient cells in myelodysplastic syndromes appear to arise from more committed progenitors.

Standardization of flow cytometry in myelodysplastic syndromes: a report from an international consortium and the European LeukemiaNet Working Group

Flow cytometry (FC) is increasingly recognized as an important tool in the diagnosis and prognosis of myelodysplastic syndromes (MDS). However, validation of current assays and agreement upon the techniques are prerequisites for its widespread acceptance and application in clinical practice. Therefore, a working group was initiated (Amsterdam, 2008) to discuss and propose standards for FC in MDS. In 2009 and 2010, representatives from 23, mainly European, institutes participated in the second and third European LeukemiaNet (ELN) MDS workshops. In the present report, minimal requirements to analyze dysplasia are refined. The proposed core markers should enable a categorization of FC results in cytopenic patients as 'normal', 'suggestive of', or 'diagnostic of' MDS. An FC report should include a description of validated FC abnormalities such as aberrant marker expression on myeloid progenitors and, furthermore, dysgranulopoiesis and/or dysmonocytopoiesis, if at least two abnormalities are evidenced. The working group is dedicated to initiate further studies to establish robust diagnostic and prognostic FC panels in MDS. An ultimate goal is to refine and improve diagnosis and prognostic scoring systems. Finally, the working group stresses that FC should be part of an integrated diagnosis rather than a separate technique.