Acute myeloblastic leukemia in paroxysmal nocturnal hemoglobinuria. Evidence of evolution from the abnormal paroxysmal nocturnal hemoglobinuria clone

Secondary myelodysplastic syndrome and leukemia in acquired aplastic anemia and paroxysmal nocturnal hemoglobinuria

Acquired aplastic anemia (AA) and paroxysmal nocturnal hemoglobinuria (PNH) are pathogenically related nonmalignant bone marrow failure disorders linked to T-cell-mediated autoimmunity; they are associated with an increased risk of secondary myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). Approximately 15% to 20% of AA patients and 2% to 6% of PNH patients go on to develop secondary MDS/AML by 10 years of follow-up. Factors determining an individual patient's risk of malignant transformation remain poorly defined. Recent studies identified nearly ubiquitous clonal hematopoiesis (CH) in AA patients. Similarly, CH with additional, non-PIGA, somatic alterations occurs in the majority of patients with PNH. Factors associated with progression to secondary MDS/AML include longer duration of disease, increased telomere attrition, presence of adverse prognostic mutations, and multiple mutations, particularly when occurring early in the disease course and at a high allelic burden. Here, we will review the prevalence and characteristics of somatic alterations in AA and PNH and will explore their prognostic significance and mechanisms of clonal selection. We will then discuss the available data on post-AA and post-PNH progression to secondary MDS/AML and provide practical guidance for approaching patients with PNH and AA who have CH.

PIG-A mutations in paroxysmal nocturnal hemoglobinuria and in normal hematopoiesis

PIG-A is an X-linked gene that is essential for the first step in the biosynthesis of glycosylphosphatidyl-inositol (GPI) anchors. A rare clonal hematopoietic stem cell disease, paroxysmal nocturnal hemoglobinuria (PNH), is caused by mutations in the PIG-A gene. PNH is an acquired disease that may arise de novo or emanate from aplastic anemia. PNH blood cells have an absence or marked deficiency of all GPI anchored proteins. Interestingly, rare GPI anchor deficient blood and marrow cells that harbor PIG-A mutations can also be found in most healthy controls. This review examines the clinical and biological relevance of PIG-A mutations in PNH, aplastic anemia and healthy controls.

A new aspect of the molecular pathogenesis of paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal hematologic disorder which is manifest by complement-mediated hemolysis, venous thrombosis, and bone marrow failure. Complement-mediated hemolysis in PNH is explained by the deficiency of glycosylphosphatidylinositol (GPI)-anchored proteins, CD55 and CD59 on erythrocyte surfaces. All the PNH patients had phosphatidylinositol glycan-class A (PIG-A) gene abnormalities in various cell types, indicating that PIG-A gene mutations cause the defects in GPI-anchored proteins that are essential for the pathogenesis of PNH. In addition, a PIG-A gene abnormality results in a PNH clone. Bone marrow failure causes cytopenias associated with a proliferative decrease of its hematopoietic stem cells and appears to be related to a pre-leukemic state. Although it is unclear how a PNH clone expands in bone marrow, it is considered that the most important hypothesis implicates negative selection of a PNH clone, but it does not explain the changes in the clinical features at the terminal stage of PNH. Recently, it has been suggested that an immune mechanism, in an HLA-restricted manner, plays an important role in the occurrence or selection of a PNH clone and GPI may be a target for cytotoxic-T lymphocytes. Also, it has been indicated that the Wilms' tumor gene (WT1) product is related to a PNH clone, but the significance of WT1 expression is not clear because of the functional diversity of the gene. To elucidate this problem, it is important to know the pathophysiology of bone marrow failure in detail and how bone marrow failure affects hematopoietic stem cells and immune mechanisms in bone marrow failure syndromes.

Acute myelogenous leukemia with PIG-A gene mutation evolved from aplastic anemia-paroxysmal nocturnal hemoglobinuria syndrome

We report a patient with aplastic anemia (AA)-paroxysmal nocturnal hemoglobinuria (PNH) syndrome who developed acute myelogenous leukemia (AML). Flow cytometric analysis showed that the leukemic cells in the bone marrow lacked CD59 antigen on their surface and were positive for P-glycoprotein. Heteroduplex and single-strand conformation polymorphism analysis followed by sequencing of the leukemic cells in the bone marrow disclosed 1 frameshift-type mutation in exon 2 of the phosphatidylinositol glycan-class A (PIG-A) gene, which deductively produces truncated PIG-A protein. These findings provide direct evidence that the leukemic cells evolved from the affected PNH clone. Cytogenetic analysis in the bone marrow in each stage of AA-PNH, AML, and at relapse of AML showed normal, -7, and -7 plus -20, respectively, showing evidence of a clonal evolution. Because complete remission of AML was not achieved by intensive chemotherapies, allogeneic peripheral blood stem cell transplantation (PBSCT) from the patient's HLA-matched sister was performed successfully with recovery of CD59 antigen on bone marrow hematopoietic cells; however, leukemia relapsed 4 months after PBSCT. Leukemia derived from PNH may be resistant to intensive chemotherapy, and a highly myeloablative regimen may be required for stem cell transplantation to eradicate the PNH-derived leukemia clone.

N-RAS gene mutation in patients with aplastic anemia and aplastic anemia/ paroxysmal nocturnal hemoglobinuria during evolution to clonal disease

Long-term survivors of aplastic anemia (AA) have a high incidence of clonal disorders, in particular paroxysmal nocturnal hemoglobinuria (PNH), myelodysplastic syndromes (MDS), and acute nonlymphocytic leukemia. To investigate the potential involvement of N-RAS gene mutations in the predisposition to leukemic evolution, a subset of patients at potentially increased risk for clonal disease was selected based on evidence of existing clonal evolution. Nine patients showed a monoclonal pattern of X-chromosome inactivation, 18 demonstrated a PNH clone, and in 3 MDS developed during the course of this study. No mutations were detected during the aplastic phase of disease; 2 of 3 patients with MDS after AA also showed no mutations. However, in 1 patient in whom the disease transformed from AA/PNH to MDS, a mutation of GGT → GAT at N-RAS codon 13 became detectable, whereas the PNH mutation disappeared. The authors conclude that N-RAS mutations are not an early event preceding transformation of AA or AA/PNH to leukemia. In a subset of patients, RAS mutations may occur at the time of evolution to MDS, but preexisting RAS mutations do not explain the propensity of AA to leukemogenesis. Although PNH is also associated with leukemia, this may arise in the non-PNH cells, indicating that PIG-A gene mutation is not per se oncogenic.

Glycosyl phosphatidylinositol (GPI)-anchored molecules and the pathogenesis of paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by the expansion of one or more clones of stem cells producing progeny of mature blood cells deficient in the plasma membrane expression of all glycosyl phosphatidylinositol (GPI)-anchored proteins (AP). This is due to somatic mutations in the X-linked gene PIGA, encoding one of the several enzymes required for GPI anchor biosynthesis. More than 20 GPI-APs are variously expressed on hematological cells. GPI-APs may function as enzymes, receptors, complement regulatory proteins or adhesion molecules; they are often involved in signal transduction. The absence of GPI-APs may well explain the main clinical findings of PNH, i.e., hemolysis and thrombosis in the venous system. Other aspects of PNH pathophysiology such as various degrees of bone marrow failure and the dominance of the PNH clone may also be linked to the biology and function of GPI-APs. Results of in vitro and in vivo experiments on embryoid bodies and mice chimeric for nonfunctional Piga have recently demonstrated that Piga inactivation confers no intrinsic advantage to the affected hematopoietic clone under physiological conditions; thus additional factors are required to allow for the expansion of the mutated cells. A close association between PNH and aplastic anemia suggests that immune system mediated bone marrow failure creates and maintains the conditions for the expansion of GPI-AP deficient cells. In this scenario, a PIGA mutation would render GPI-AP deficient cells resistant to the cytotoxic autoimmune attack, enabling them to emerge. Even though the 'survival advantage' hypothesis may explain all the various aspects of this intriguing disease, a formal proof of this theory is still lacking.

Clonal evolution of aplastic anaemia to myelodysplasia/acute myeloid leukaemia and paroxysmal nocturnal haemoglobinuria

Aplastic anaemia (AA) is a non-malignant haemopoietic disorder characterised by peripheral blood pancytopenia and a hypocellular bone marrow. Successful management of acquired AA including treatment with immunosuppressive agents, mainly antithymocyte globulin (ATG) and cyclosporin or allogeneic haemopoietic stem cell transplantation, has resulted in long-term survival of many patients. The later evolution of complicating clonal disorders such as paroxysmal nocturnal haemoglobinuria, myelodysplasia and acute myeloid leukaemia in patients treated with immunosuppressive therapy may be a manifestation of the natural history of the aplasia, the development of which may or may not be increased by immunosuppressive therapy. A persistent, profound deficiency and/or defect in the stem cell compartment, despite haematological recovery after immunosuppressive therapy, may create an unstable situation which predisposes to later clonal disorders. A review of the progression of AA to clonal disorders is now outlined.

Leukemia arising out of paroxysmal nocturnal hemoglobinuria

In paroxysmal nocturnal hemoglobinuria (PNH), one or more hematopoietic stem cells that are defective in GPI anchor assembly as a result of mutation in the PIG-A gene preferentially expand in the bone marrow and give rise to peripheral blood elements that are deficient in GPI anchored protein expression. According to current concepts, 5-15% of PNH patients develop leukocyte dyscrasias which invariably are acute myelogenous leukemia (AML). In this review, the literature from 1962 to the present is analyzed regarding the type of leukocyte dyscrasia, incidence, and cytogenetic features of the abnormal cells that have been reported. Among a total of 119 cases that are well-documented, 104 myeloid dyscrasias involving several categories in addition to AML, as well as 15 lymphoid dyscrasias are described. Of 1,760 patients in 15 series that contain 20 or more patients, 16 (1%) are reported as having developed "acute leukemia." However, of 288 listed as having died, 13 (5%) are recorded as having had "acute leukemia." In 32 of the patients with hematological dyscrasias where karyotypes were analyzed, 7 were found to be normal and 25 found to harbor various alterations with the +8 abnormality present in 8. In 5 of 7 instances evidence indicates that the dyscratic cell arises from the PNH clone. Processes potentially involved in the evolution of the dyscratic cells from PNH clones are discussed.

Detection of "PNH red cell" populations in hematological disorders using the Sephacryl Gel Test micro typing system

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal disorder characterised by an unusual sensitivity of abnormal red cell population(s) to complement lysis, due to a complete or incomplete defect of various surface molecules, including CD55 and CD59. PNH has been associated with various hematological disorders. Using a newly introduced method, the Sephacryl gel test microtyping system, we investigated the presence of CD55 or CD59 defective red cell populations in several hematological disorders. It was also found that a large proportion of such patients possess CD55 deficient populations, while a smaller but still significant proportion possess CD59 deficient populations. Defective red cell populations were detected in normal subjects as well. These findings need further investigation. Nevertheless the Sephacryl Gel Test microtyping system although non specific, seems to be useful in screening for the PNH and/or "PNH-like" red cell defect in several hematological disorders.

Relationship Between the Phenotypes of Circulating Erythrocytes and Cultured Erythroblasts in Paroxysmal Nocturnal Hemoglobinuria

To investigate erythropoiesis in paroxysmal nocturnal hemoglobinuria (PNH), we studied the expression of glycosylphosphatidylinositol (GPI)-anchored membrane proteins on circulating erythrocytes and erythroblasts obtained by erythropoietic cell culture in nine patients with this disease. One-color and two-color flow cytometric analyses were performed using monoclonal antibodies for decay-accelerating factor (DAF ) and/or CD59/membrane attack complex-inhibitory factor (MACIF). In addition, terminal deoxynucleotidyl transferase–mediated dUTP-biotin nick end-labeling (TUNEL) analysis was performed to assess apoptosis of erythroblasts from six patients. On flow cytometric analysis, cases 1 to 6 had positive and negative erythrocyte populations, case 7 intermediate and negative populations, case 8 positive, intermediate, and negative populations, and case 9 a single double-negative population. In addition, cases 1 to 6 and 8 had positive, intermediate, and negative erythroblast populations, while cases 7 and 9 had intermediate and negative populations. The percentage of double-negative erythrocytes showed a significant correlation with that of double-negative erythroblasts (r = .741, P < .05). In seven of nine patients, more erythroblasts than erythrocytes were negative for the two membrane proteins. Also, some patients with an intermediate population of erythrocytes did not necessarily show an increase of PNH II erythroblasts. Apoptosis of PNH erythroblasts was also detected, but the percentage of apoptotic cells in PNH patients showed no difference from that in healthy volunteers. These findings suggest that the final phenotype of mature erythrocytes in PNH is determined during maturation from erythroblasts to erythrocytes by the disappearance or persistence of PNH II erythroblasts. In addition, PNH erythroblasts in vitro may be partly lost by apoptosis, but apoptosis does not play an important role in determining GPI-linked protein expression.

Relationship Between the Phenotypes of Circulating Erythrocytes and Cultured Erythroblasts in Paroxysmal Nocturnal Hemoglobinuria

To investigate erythropoiesis in paroxysmal nocturnal hemoglobinuria (PNH), we studied the expression of glycosylphosphatidylinositol (GPI)-anchored membrane proteins on circulating erythrocytes and erythroblasts obtained by erythropoietic cell culture in nine patients with this disease. One-color and two-color flow cytometric analyses were performed using monoclonal antibodies for decay-accelerating factor (DAF ) and/or CD59/membrane attack complex-inhibitory factor (MACIF). In addition, terminal deoxynucleotidyl transferase–mediated dUTP-biotin nick end-labeling (TUNEL) analysis was performed to assess apoptosis of erythroblasts from six patients. On flow cytometric analysis, cases 1 to 6 had positive and negative erythrocyte populations, case 7 intermediate and negative populations, case 8 positive, intermediate, and negative populations, and case 9 a single double-negative population. In addition, cases 1 to 6 and 8 had positive, intermediate, and negative erythroblast populations, while cases 7 and 9 had intermediate and negative populations. The percentage of double-negative erythrocytes showed a significant correlation with that of double-negative erythroblasts (r = .741, P &lt; .05). In seven of nine patients, more erythroblasts than erythrocytes were negative for the two membrane proteins. Also, some patients with an intermediate population of erythrocytes did not necessarily show an increase of PNH II erythroblasts. Apoptosis of PNH erythroblasts was also detected, but the percentage of apoptotic cells in PNH patients showed no difference from that in healthy volunteers. These findings suggest that the final phenotype of mature erythrocytes in PNH is determined during maturation from erythroblasts to erythrocytes by the disappearance or persistence of PNH II erythroblasts. In addition, PNH erythroblasts in vitro may be partly lost by apoptosis, but apoptosis does not play an important role in determining GPI-linked protein expression.

Paroxysmal nocturnal hemoglobinuria as a molecular disease

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired, clonal disorder of hematopoietic cells caused by somatic mutation in the X-linked PIGA gene encoding a protein involved in the synthesis of the glycosylphosphatidylinositol (GPI) anchor by which many proteins are attached to the membrane of cells. About 15 proteins have been found to be lacking or markedly deficient on the abnormal blood cells. These defects result in a clinical syndrome that includes intravascular hemolysis mediated by complement, unusual venous thromboses, deficits of hematopoiesis, and other manifestations. Therapy is presently directed mainly at the consequences of the disorder rather than its basic causes and includes replacement of iron, folic acid, and whole blood; hormonal modulation (prednisone, androgens); anticoagulation; and bone marrow transplantation. PNH is a chronic disease with more than half of adult patients surviving 15 years or more; prognosis is less good in children.

A novel class of cell surface glycolipids of mammalian cells. Free glycosyl phosphatidylinositols

Glycosyl phosphatidylinositol (GPI) lipids function as anchors of membrane proteins, and free GPI units serve as intermediates along the path of GPI-anchor biosynthesis. By using in vivo cell surface biotinylation, we show that free GPIs: 1) can exit the rough endoplasmic reticulum and are present on the surface of a murine EL-4 T-lymphoma and a human carcinoma cell (HeLa), 2) arrive at the cell surface in a time and temperature-dependent fashion, and 3) are built on a base-labile glycerol backbone, unlike GPI anchors of surface proteins of the same cells. The free GPIs described in this study may serve as a source of hormone-sensitive phosphoinositol glycans. The absence of free GPIs from the cell surface may also account for the growth advantage of blood cells in paroxysmal nocturnal hemoglobinuria.

Mechanisms by which the surface expression of the glycosyl-phosphatidylinositol-anchored complement regulatory proteins decay-accelerating factor (CD55) and CD59 is lost in human leukaemia cell lines

We have investigated the mechanisms of defects in the glycosyl-phosphatidylinositol (GPI)-anchored complement regulatory proteins delay-accelerating factor (DAF) and/or CD59 in a panel of human leukaemia cell lines that lack surface expression of these proteins: U937 (DAF+/CD59-), CEM (DAF-/CD59+), TALL (DAF-/CD59-) and a substrain of Ramos [Ramos(-)] (DAF-/CD59-). Northern blotting and reverse transcription-PCR revealed that the main cause of the DAF and/or CD59 deficiency is the failure of mRNA expression in most of the cell lines, except in Ramos(-) in which sufficient mRNA for DAF and CD59 was produced. U937, CEM and TALL cells were not defective in GPI anchor formation as assessed by the detection of other GPI-anchored proteins. No gene abnormality corresponding to DAF or CD59 was detected by Southern blotting. Thus the cause of the defects of DAF and/or CD59 in these leukaemia cell lines except for Ramos(-) is virtually undetectable steady-state levels of the relevant mRNA, most likely attributable to lack of transcription in these cell lines. On the other hand, Ramos(-) cells failed to generate a GPI anchor, whereas they normally expressed DAF and CD59 transcripts. The transfection of phosphatidylinositol-glycan class A (PIG-A) cDNA into Ramos(-) cells restored DAF and CD59 expression, indicating that the defective mechanism in GPI anchor formation is similar to that in paroxysmal noctural haemoglobinuria (PNH) cells, i.e. a deficiency of the PIG-A gene product. Thus the mechanisms of the defects of DAF and/or CD59 in human leukaemia cell lines are not uniform, and in most cases are different from that proposed to cause PNH.

Anti-thymocyte globulin treatment of a patient for paroxysmal nocturnal haemoglobinuria-aplastic anaemia syndrome: complement activation and transient decrease of the PNH clone

Paroxysmal nocturnal haemoglobinuria (PNH) is an acquired clonal stem cell disorder resulting in insufficient and defective haematopoesis associated frequently with aplastic anaemia (AA). A deficiency of the glycosyl phosphatidylinositol (GPI)-anchored complement activation regulatory proteins CD55 and CD59 is responsible for an increased sensitivity of erythrocytes to complement attack leading to chronic intravascular haemolysis with haemoglobinuria. In this study we investigated the effects of complement activation caused by anti-thymocyte globulin (ATG) treatment on the PNH clone in a patient affected with the PNH/AA-syndrome. Fluid phase complement components C3, C4, C6 and terminal complement complex (TCC) were assayed by ELISA. CD55, CD59 and cell-associated TCC were monitored by flow cytometry. ATG treatment resulted in profound systemic complement activation which led to a decrease in the levels of native C3 and C4 to 65% and 40%, respectively, of the original levels on day 5 and of C6 and TCC to 61% and 23%, respectively, on day 10. A return to pre-treatment levels was observed for C3 by day 15, for C6 by day 30 and for C4 by day 90. Flow cytometry revealed that the deficiency in the GPI-anchored protein was restricted to granulocytes, while lymphocytes remained unaffected. Cell-bound TCC increased by 1.67-fold and 2.37-fold on day 5 and day 10, respectively, decreasing to 1.40-fold and 1.30-fold on day 15 and day 30, respectively. The percentage of PNH granulocytes as identified by the absence of the CD55- and CD59-antigens exhibited a temporary decrease from 72% on day 0 to 65% on day 5 and 59% on day 10 and returned thereafter to the original percentage of 70% by day 15 and exceeding this level to 76% on day 30 and 79% on day 90. We report profound activation of the classical pathway of the complement cascade and the terminal complement complex by the globulin leading to a transient decrease of the PNH clone, presumably due to subsequent lysis of the PNH cells devoid of complement regulatory proteins.

Natural history of paroxysmal nocturnal hemoglobinuria

BACKGROUND

Paroxysmal nocturnal hemoglobinuria (PNH), which is characterized by intravascular hemolysis and venous thrombosis, is an acquired clonal disorder associated with a somatic mutation in a totipotent hematopoietic stem cell. An understanding of the natural history of PNH is essential to improve therapy.

METHODS

We have followed a group of 80 consecutive patients with PNH who were referred to Hammersmith Hospital, London, between 1940 and 1970. They were treated with supportive measures, such as oral anticoagulant therapy after established thromboses, and transfusions.

RESULTS

The median age of the patients at the time of diagnosis was 42 years (range, 16 to 75), and the median survival after diagnosis was 10 years, with 22 patients (28 percent) surviving for 25 years. Sixty patients have died; 28 of the 48 patients for whom the cause of death is known died from either venous thrombosis or hemorrhage. Thirty-one patients (39 percent) had one or more episodes of venous thrombosis during their illness. Of the 35 patients who survived for 10 years or more, 12 had a spontaneous clinical recovery. No PNH-affected cells were found among the erythrocytes or neutrophils of the patients in prolonged remission, but a few PNH-affected lymphocytes were detectable in three of the four patients tested. Leukemia did not develop in any of the patients.

CONCLUSIONS

PNH is a chronic disorder that curtails life. A spontaneous long-term remission can occur, which must be taken into account when considering potentially dangerous treatments, such as bone marrow transplantation. Platelet transfusions should be given, as appropriate, and long-term anticoagulation therapy should be considered for all patients.

Myelodysplasia in a patient with pre-existing paroxysmal nocturnal haemoglobinuria: a clonal disease originating from within a clonal disease

Paroxysmal nocturnal haemoglobinuria (PNH) is an acquired haemolytic anaemia, clonal in nature, due to somatic mutation. PNH may evolve to aplastic anaemia; more rarely to a myelodysplastic syndrome (MDS) or to acute myeloid leukaemia (AML). We have studied a patient who suffered from PNH and later developed refractory anaemia with ringed sideroblasts (RARS) associated with trisomy 8. By testing peripheral blood cells with appropriate antibodies we have shown that all of the red cells, neutrophils and monocytes, as well as 20% of the lymphocytes, belonged to the PNH clone; in contrast, only 43% of neutrophils and 22% of monocytes belonged to the MDS clone. We infer that the MDS must have arisen from within the PNS clone.

Analysis of cytoplasmic and surface antigens in childhood T-cell acute lymphoblastic leukaemias: clinical relevance of cytoplasmic TCR beta chain expression

Expression of surface and cytoplasmic antigens on the blasts from 42 cases of childhood T-cell acute lymphoblastic leukaemia (T-ALL) were analysed. All with childhood T-ALL, except for one case expressing cytoplasmic TCR delta chain, were classified on the basis of differential expression of cytoplasmic CD3 (cCD3), TCR beta chain (cTCR beta) and surface CD3 (sCD3) into the following three groups: group I (cCD3+, cTCR beta-, sCD3-), eight cases (19.5%); group II (cCD3+, cTCR beta +, sCD3-), 23 cases (56.1%); group III (cCD3+, cTCR beta +/-, sCD3+), 10 cases (24.4%). Each group defines the stepwise maturational stage of the CD3/TCR complex along the intrathymic T-cell differentiation. Group I had the lowest initial WBC count among the three groups (P < 0.05) and showed significantly (P < 0.05) a higher event-free survival (0.75) than those of group II (0.33). There was no significant difference in both the initial WBC count and the event-free survival between groups II and III. Thus, the absence of cTCR beta in sCD3-negative T-ALL appears to be a good prognostic factor, suggesting that this classification provides a useful tool to predict the prognosis of childhood T-ALL. This is the first report, to our knowledge, studying the relationship between the expression of cytoplasmic CD3/TCR antigens and the clinical features in T-ALL.

Myelodysplasia following paroxysmal nocturnal haemoglobinuria: evidence for the emergence of a separate clone

A patient with paroxysmal nocturnal haemoglobinuria (PNH) who developed a myelodysplastic syndrome (MDS) is described. After the onset of myelodysplasia the neutrophils of the patient fully expressed GPI-linked proteins. It is concluded that the myelodysplasia does not originate from transformed PNH stem cells, but represents the emergence of a separate clone arising from an injured marrow.

Paroxysmal nocturnal hemoglobinuria with myelofibrosis: progression to acute myeloblastic leukemia

A 58-year-old male was diagnosed as having paroxysmal nocturnal hemoglobinuria (PNH) with myelofibrosis in 1984. The administration of hydroxyurea and low dose splenic irradiation were initiated for abdominal distention due to splenomegaly in 1987. In May 1990 the patient developed smouldering acute myeloblastic leukemia (AML); and the blasts proliferated in response to G-CSF administered for refractory pneumonia. The patient died of pneumonia and pleural involvement of leukemia in September 1990. FACS analysis of the blasts using anti-decay accelerating factor (DAF) (CD55) and CD59 (membrane attack complex inhibition factor: MACIF) monoclonal antibodies demonstrated that 25.5% and/or 87.3% of the blasts were negative for DAF or CD59 respectively. There is the earlier evidence that about 90% leukemic myeloblasts from non-PNH AML patients are positive for DAF, and nearly 100% of non-PNH neutrophils have been shown to be positive for both DAF and CD59. Our data suggest that the leukemic blasts from this patient may have derived from the PNH clone.

Membrane proteins in paroxysmal nocturnal haemoglobinuria

A review of recent information on the abnormalities of the blood cell membrane in paroxysmal nocturnal haemoglobinuria (PNH) is presented, with a detailed analysis of biochemical and flow cytometry findings. The complex patterns observed in the various cell lineages of which the PNH clone consists are described, and a simplified monoclonal antibody panel is defined for diagnostic purposes. Available data on in vitro culture of progenitor cells and on the recent establishment of PNH cell lines are summarized. Finally, we discuss speculative hypotheses on the growth advantage of the PNH clone.

Paroxysmal nocturnal hemoglobinuria: correction of abnormal phenotype by somatic cell hybridization

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired blood disorder thought to result from a somatic mutation in a hemopoietic stem cell. PNH may evolve to aplastic anemia or to acute leukemia. PNH cells are deficient in proteins attached to the cell membrane via a glycosylphosphatidylinositol structure, called the GPI anchor, and the primary lesion in PNH is thought to be a defect in the biosynthesis of the GPI anchor. We have recently established permanent lymphoblastoid cell lines that have the PNH phenotype and we report now the isolation of human-human somatic cell hybrid clones obtained by fusing them with normal lymphoblastoid cells. In all of 21 hybrid clones, obtained from five different patients, the expression of three different GPI-linked proteins on the hybrid cells was normal. These findings indicate that the PNH mutant gene is recessive with respect to the normal allele and that a recessive mutation can cause a clonal preneoplastic disorder.

Paroxysmal nocturnal hemoglobinuria as a marker for clonal myelopathy

Paroxysmal nocturnal hemoglobinuria (PNH) is recognized as a clonal disorder manifested as increased sensitivity of marrow cells to complement. Case reports have associated this condition with leukemia, myelodysplasia, and myeloproliferative disorders. We identified 47 patients with PNH from 1976 to 1990. In 9 of the 47 patients, PNH was associated with another clonal myelopathy. Five patients had PNH and a myelodysplastic syndrome, and four had PNH and agnogenic myeloid metaplasia. PNH preceded the development of myelodysplastic syndrome but occurred after the development of agnogenic myeloid metaplasia. This is the largest series of PNH and other clonal myelopathies. We suggest that the PNH defect may represent a second manifestation of a single stem cell disorder.

Trisomy 8 detection in granulomonocytic, erythrocytic and megakaryocytic lineages by chromosomal in situ suppression hybridization in a case of refractory anaemia with ringed sideroblasts complicating the course of paroxysmal nocturnal haemoglobinuria

Paroxysmal nocturnal haemoglobinuria (PNH) was diagnosed in a 20-year-old male patient who suffered from anaemia since the age of 11. Eighteen years after diagnosis, PNH transformed into refractory anaemia with ringed sideroblasts (RARS). Trisomy 8 was observed in 27%, 45% and 53% of the bone marrow metaphase cells analysed in 1987, 1988 and 1990 respectively. In order to determine which bone marrow cell lineages were affected by trisomy 8 and at which stage of stem cell differentiation, MAC (Morphology, Antibody, Chromosomes) and CISS (Chromosomal In Situ Suppression) hybridization techniques were combined. The MAC technique enables karyotypic analysis of morphologically and immunologically classified mitotic cells. CISS hybridization makes it possible to detect individual chromosomes and chromosome aberrations using recombinant DNA libraries from sorted human chromosomes. Trisomy 8 was detected in granulomonocytic (50.6%), erythrocytic (67.2%) and megakaryocytic (one megakaryocyte with trisomy 8, one normal) lineages, providing evidence for the occurrence of trisomy 8 in early haematopoietic cell precursors, at the GEMM or pluripotent level. Cytogenetic and clinical data suggest that the sideroblastic clone originated from a mutation affecting a cell of the PNH clone, progressively replaced by the PNH/RARS clone, due to proliferative advantage.

Diagnosis of paroxysmal nocturnal haemoglobinuria using immunophenotyping of peripheral blood cells

Paroxysmal nocturnal haemoglobinuria (PNH) is now generally accepted as a disease in which bone marrow derived cells are deficient in phosphatidylinositolglycan (PIG)-anchored surface molecules. A series of new monoclonal antibodies detecting PIG-anchored surface structures on human leucocytes (CD48, CD55, CD59) has recently been described. In the present study 12 patients with the diagnosis PNH and a positive Ham test were examined for PIG-anchored surface antigen expression on various cell lineages using immunofluorescence. In all patients deficient cells were detected in erythrocyte, granulocyte and monocyte analysis. A deficient lymphocyte subset was also observed in all but one of these patients. Using two-colour analysis, all lymphocyte subpopulations such as T, B and NK cells were found to be affected. In addition, peripheral blood cells of 22 patients with severe aplastic anaemia (SAA) were tested for the PIG-anchoring defect. In five of these patients the defect was detected, and in four of the five the lack of PIG-anchored molecules was confined to the granulocyte and monocyte lineages apparently without affecting the erythrocytes. The results of these studies demonstrate that cytofluorographic testing of peripheral blood cells provides a simple and reliable method for establishing the diagnosis of PNH. Furthermore, especially in the case of aplastic anaemia patients, the sensitivity of immunophenotyping might be superior to conventional laboratory tests.

Paroxysmal nocturnal hemoglobinuria with onset in childhood and adolescence

BACKGROUND

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal hematologic disorder characterized by hemoglobinuria, thrombosis, infection, and a tendency toward bone marrow aplasia. Onset usually occurs in adulthood. Few children and adolescents with PNH have been described, and data on diagnosis, clinical course, and survival in young patients are unavailable.

METHODS

We retrospectively reviewed clinical and laboratory data on all patients 21 years old or younger in whom PNH had been diagnosed at Duke University Medical Center from 1966 to 1991.

RESULTS

Medical records and clinical follow-up data were available for 26 young patients. Although 50 percent of adult patients present with hemoglobinuria, only four of our patients (15 percent) presented with this feature. In contrast, 15 of our patients (58 percent) had moderate or severe bone marrow failure at presentation, as compared with about 25 percent of adults in cases from the literature; all 26 patients eventually had evidence of bone marrow dysfunction. Eight patients (31 percent) have died, with a median survival of 13.5 years since their initial symptoms.

CONCLUSIONS

Children and adolescents with PNH have a greater prevalence of bone marrow failure than do adults with this disorder, and their morbidity and mortality are high. Bone marrow transplantation should be considered for selected young patients with PNH.

Altered expression of gangliosides in erythrocytes of paroxysmal nocturnal hemoglobinuria

In paroxysmal nocturnal hemoglobinuria (PNH), impaired glycosyl-phosphatidylinositol (PI)-anchoring of membrane proteins such as decay-accelerating factor has been known to lead to increased susceptibility to complement. Moreover, abnormal expression of non-PI-anchoring glycoproteins such as C3b/C4b receptor (CR1) or glycophorin-alpha also has been shown in PNH. Therefore, we biochemically analyzed glycosphingolipids (GSL) as one of the membrane glycoconjugates of PNH erythrocytes. Erythrocytes of all seven PNH patients showed altered expression of sialosyl GSL (gangliosides) as compared with the control erythrocytes of healthy donors. Both a sialosylparagloboside (IV6NeuAc-nLc4Cer) among four major gangliosides and some minor gangliosides in normal erythrocytes variably disappeared in erythrocytes from the peripheral blood of PNH patients. As one of the possible mechanisms of altered expression of gangliosides in PNH erythrocytes, structural analysis suggested impaired sialylation of GSL. These results suggest not only the altered metabolism of gangliosides in PNH erythrocytes, but also a metabolic disorder of membrane glycoconjugates as a new feature of PNH.

[Paroxysmal nocturnal hemoglobinuria]

Paroxysmal nocturnal hemoglobinuria, first described in the late 19th century, is an acquired disorder characterized by hemoglobinemia and hemoglobinuria. The major clinical manifestation of PNH is chronic intravascular hemolysis of various severity. Patients-mostly young adults - may also present with episodes of abdominal or back pain. Common cause of death is thrombosis especially of the hepatic veins. Granulocytopenia and thrombocytopenia may be the initial manifestation of PNH, indicating that the disorder is a primary bone-marrow disease, affecting not only the erythrocytes but also other peripheral blood cells and the haematopoietic stem cell. The course of the disease is variable. Partial complete recovery was described, but also fatal thrombosis. The major phenotypic expression of PNH is an increased susceptibility of the erythrocytes to the lytic action of complement in vitro. The enhanced complement susceptibility is most probably due to membrane defects: two membrane proteins regulating the complement cascade in PNH cells were missing, the decay-accelerating factor, DAF, inhibiting the activation of the lytic complement complex and the C8 binding protein, C8bp, which interferes with the lytic process. Aside from the lack of the complement regulators also other membrane defects have been described (e.g. of acetylcholinesterase or alkaline phosphatase). The proteins as well as DAF and C8bp are linked to the cell membrane via a phosphatidylinositol (PI) anchor, leading to the speculation that the disease results from a deficiency in the post-translational PI anchoring mechanism. The diagnosis of PNH is based on the Hamtest, but will be extended to the quantitation of the above described membrane proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Paroxysmal nocturnal hemoglobinuria: the biochemical defects and the clinical syndrome

Paroxysmal nocturnal hemoglobinuria is a disorder characterized by the lack of membrane proteins affixed to the membrane by an anchor dependent upon phosphatidyl inositol, suggesting that some acquired abnormality in the metabolism of this class of proteins is basic to the disease. Most of the clinical symptoms can be explained by the lack of these proteins. However, much work is needed to understand completely the relationship of the biochemical facts and the clinical syndrome.