Background

P.N.H. or paroxysmal nocturnal hemoglobinuria is a rare and potentially devastating disease. Only recently has research allowed a better understanding of the intricate mechanisms behind the development of the disease, highlighted in the pathogenesis section. It is an acquired clonal defect of hematopoietic stem cells. Patients present with anemia, usually as young adults.

OUTLINE

Epidemiology
Disease Associations
Pathogenesis
Laboratory/Radiologic/Other Diagnostic Testing
Gross Appearance and Clinical Variants
Prognosis and Treatment
Commonly Used Terms
Internet Links

EPIDEMIOLOGY	CHARACTERIZATION
INCIDENCE
Paroxysmal nocturnal hemoglobinuria cells in patients with bone marrow failure syndromes. Dunn DE, Tanawattanacharoen P, Boccuni P, Nagakura S, Green SW, Kirby MR, Kumar MS, Rosenfeld S, Young NS. National Heart, Lung, and Blood Institute, Bethesda, Maryland 20892-1652, USA.	Ann Intern Med 1999 Sep 21;131(6):401-8 Abstract quote BACKGROUND: Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired hematopoietic stem-cell disorder in which the affected cells are deficient in glycosylphosphatidylinositol (GPI)-anchored proteins. Paroxysmal nocturnal hemoglobinuria is frequently associated with aplastic anemia, although the basis of this relation is unknown. OBJECTIVE: To assess the PNH status of patients with diverse marrow failure syndromes. DESIGN: Correlation of cytofluorometric data with clinical features. SETTING: Hematology Branch, National Heart, Lung, and Blood Institute, Bethesda, Maryland. PATIENTS: 115 patients with aplastic anemia, 39 patients with myelodysplasia, 28 patients who had recently undergone bone marrow transplantation, 18 patients with cancer that was treated with chemotherapy, 13 patients with large granular lymphocytosis, 20 controls who had received renal allografts, and 21 healthy participants. INTERVENTION: Patients with aplastic anemia, myelodysplasia, or renal allografts received antithymocyte globulin. MEASUREMENTS: Flow cytometry was used to assess expression of GPI-anchored proteins on granulocytes. RESULTS: Evidence of PNH was found in 25 of 115 (22%) patients with aplastic anemia. No patient with normal GPI-anchored protein expression at presentation developed PNH after therapy (n = 16). Nine of 39 (23%) patients with myelodysplasia had GPI-anchored protein-deficient cells. Abnormal cells were not detected in patients with constitutional or other forms of bone marrow failure or in renal allograft recipients who had received antithymocyte globulin. Aplastic anemia is known to respond to immunosuppressive therapy; in myelodysplasia, the presence of a PNH population was strongly correlated with hematologic improvement after administration of antithymocyte globulin (P = 0.0015). CONCLUSIONS: Flow cytometric analysis is superior to the Ham test and permits concomitant diagnosis of PNH in about 20% of patients with myelodysplasia (a rate similar to that seen in patients with aplastic anemia). The presence of GPI-anchored protein-deficient cells in myelodysplasia predicts responsiveness to immunosuppressive therapy. Early emergence of GPI-anchored protein-deficient hematopoiesis in a patient with marrow failure may point to an underlying immune pathogenesis.

 

DISEASE ASSOCIATIONS	CHARACTERIZATION
HLA
Increased frequency of HLA-DR2 in patients with paroxysmal nocturnal hemoglobinuria and the PNH/aplastic anemia syndrome. Maciejewski JP, Follmann D, Nakamura R, Saunthararajah Y, Rivera CE, Simonis T, Brown KE, Barrett JA, Young NS. Hematology Branch and Office of Biostatistics Research, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA	Blood 2001 Dec 15;98(13):3513-9 Abstract quote Many autoimmune diseases are associated with HLA alleles, and such a relationship also has been reported for aplastic anemia (AA). AA and paroxysmal nocturnal hemoglobinuria (PNH) are related clinically, and glycophosphoinositol (GPI)-anchored protein (AP)-deficient cells can be found in many patients with AA. The hypothesis was considered that expansion of a PNH clone may be a marker of immune-mediated disease and its association with HLA alleles was examined. The study involved patients with a primary diagnosis of AA, patients with myelodysplastic syndrome (MDS), and patients with primary PNH. Tests of proportions were used to compare allelic frequencies. For patients with a PNH clone (defined by the presence of GPI-AP-deficient granulocytes), regardless of clinical manifestations, there was a higher than normal incidence of HLA-DR2 (58% versus 28%; z = 4.05). The increased presence of HLA-DR2 was found in all frankly hemolytic PNH and in PNH associated with bone marrow failure (AA/PNH and MDS/PNH). HLA-DR2 was more frequent in AA/PNH (56%) than in AA without a PNH clone (37%; z = 3.36). Analysis of a second cohort of patients with bone marrow failure treated with immunosuppression showed that HLA-DR2 was associated with a hematologic response (50% of responders versus 34% of nonresponders; z = 2.69). Both the presence of HLA-DR2 and the PNH clone were independent predictors of response but the size of PNH clone did not correlate with improvement in blood count. The results suggest that clonal expansion of GPI-AP-deficient cells is linked to HLA and likely related to an immune mechanism.
LYMPHOPROLIFERATIVE DISORDERS
An unusual association of monoclonal gammopathy, paroxysmal nocturnal haemoglobinuria and myelodysplastic syndrome transformed into acute myeloid leukaemia: coexistence of triple clonal disorders. Watanabe J, Kondo H, Iwazaki H, Hatake K, Horikoshi N. Division of Clinical Chemotherapy, Cancer Chemotherapy Centre, Japanese Foundation for Cancer Research, Tokyo, Japan.	Leuk Lymphoma 2001 Aug;42(4):813-7 Abstract quote An unusual association of paroxysmal nocturnal haemoglobinuria (PNH), myelodysplastic syndrome (MDS), acute myeloid leukaemia (AML) and monoclonal gammopathy is reported. A 60-year old male, who had a history of IgA monoclonal gammopathy, presented with haemoglobinuria and colic pain. Flow cytometry showed CD55negative/59dim peripheral red cells, and bone marrow examination disclosed MDS. Eleven months, he developed later AML with disappearance of the PNH clones, although the monoclonal gammopathy persisted. The relationship between PNH and MDS has not fully been assessed, although our findings indicate that these triple clonal disorders, all coexisted in one patient.
Association of clonal T-cell large granular lymphocyte disease and paroxysmal nocturnal haemoglobinuria (PNH): further evidence for a pathogenetic link between T cells, aplastic anaemia and PNH. Karadimitris A, Li K, Notaro R, Araten DJ, Nafa K, Thertulien R, Ladanyi M, Stevens AE, Rosenfeld CS, Roberts IA, Luzzatto L. Department of Human Genetics, Memorial Sloan-Kettering Cancer Center, New York, NY, USA.	Br J Haematol 2001 Dec;115(4):1010-4 Abstract quote There is mounting evidence to suggest that T-cell-mediated suppression of haemopoiesis is a pathogenetic mechanism in three bone marrow failure syndromes: aplastic anaemia (AA), paroxysmal nocturnal haemoglobinuria (PNH) and myelodysplasia (MDS). T-cell microclones can be detected by sensitive polymerase chain reaction (PCR)-based methods in all three disorders. Recently, larger clonal populations of T-cell large granular lymphocytes (T-LGLs) have been observed in some patients with AA and MDS. Here, we report the development of a large clonal T-LGL population in a patient with bona fide PNH. In this patient, we defined part of the sequence of the T-cell receptor (TCR) beta-chain gene, and we have shown that the large T-LGL population emerged from a background of multiple smaller T-cell clones. Thus, T-LGL clones in AA, MDS and PNH probably expand as a result of antigenic stimulation. It is postulated that the antigen driving clonal T-cell proliferations in these disorders exists on haemopoietic stem cells.
Detection of CD55- and/or CD59-deficient red cell populations in patients with lymphoproliferative syndromes. Meletis J, Terpos E, Samarkos M, Meletis C, Apostolidou E, Komninaka V, Korovesis K, Mavrogianni D, Boutsis D, Variami E, Viniou N, Konstantopoulos K, Loukopoulos D. First Department of Internal Medicine, University of Athens School of Medicine, Laiko General Hospital, Athens, Greece.	Hematol J 2001;2(1):33-7 Abstract quote INTRODUCTION:: Paroxysmal nocturnal hemoglobinuria is an acquired clonal stem cell disorder characterized by the decrease or absence of glycosylphosphatidylinositol-anchored molecules from the surface of the affected cells, such as CD55 and CD59, resulting in chronic intravascular hemolysis, cytopenia and increased tendency to thrombosis. PNH-phenotype has been described in various hematological disorders, mainly in aplastic anemia and myelodysplastic syndromes, while it has been reported that complete deficiency of CD55 and CD59 has also been found in patients with lymphoproliferative syndromes, like non-Hodgkin's lymphomas. MATERIALS AND METHODS: The presence of CD55- and/or CD59-defective red cell populations was evaluated in 217 patients with lymphoproliferative syndromes. The study population included 87 patients with NHL, 55 with HD, 49 with CLL, 22 with ALL and four with hairy cell leukemia. One hundred and twenty-one healthy blood donors and seven patients with PNH were also studied as control groups. The sephacryl gel microtyping system was performed for the detection of CD55- and CD59-deficient red cell populations. Ham and sucrose lysis tests were also performed in all samples with CD55 or CD59 negative populations. RESULTS:: Red cell populations deficient in both CD55 and CD59 molecules were detected in 9.2% of patients with lymphoproliferative syndromes (more often in ALL and nodular sclerosis type of HD) and in all PNH patients. CD55-deficient red cell populations were found in 8.7% of LPS patients (especially in low grade B-cell NHL), while CD59-deficient populations were found in only two patients with low grade B-cell NHL. CONCLUSION:: These data indicate a possible association between paroxysmal nocturnal hemoglobinuria phenotype and lymphoproliferative syndromes, while further investigation is necessary to work out the mechanisms and the significance of the existence of this phenotype in these patients.
Detection of CD55- and/or CD59-deficient red cell populations in patients with plasma cell dyscrasias. Meletis J, Terpos E, Samarkos M, Meletis C, Apostolidou E, Komninaka V, Korovesis K, Anargyrou K, Benopoulou O, Mavrogianni D, Variami E, Viniou N, Konstantopoulos K. First Department of Internal Medicine, University of Athens School of Medicine, Laiko General Hospital, Greece.	Int J Hematol 2002 Jan;75(1):40-4 Abstract quote Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal disorder characterized by a decrease or absence of glycosylphosphatidylinositol (GPI)-anchored molecules such as CD55 and CD59 from the surface of affected cells, resulting in intravascular hemolysis, cytopenia, and venous thrombosis. A PNH-like phenotype has been detected in various hematological disorders, mainly in aplastic anemia and myelodysplastic syndromes, but also in lymphoproliferative syndromes (LPSs). To the best of our knowledge, CD55- or CD59-deficient red cells have not been detected in plasma cell dyscrasias (PCDs). The aim of this study was the detection of CD55- and/or CD59-deficient red cell populations in patients with PCD. Seventy-seven patients were evaluated; 62 with multiple myeloma (MM), 7 with Waldenstrom macroglobulinemia (WM), 6 with monoclonal gammopathy of undetermined significance (MGUS), and 2 with heavy chain disease (HCD). The sephacryl gel microtyping system was applied; Ham and sucrose lysis tests were also performed on all samples with CD55- or CD59-negative populations. Red cells deficient in both molecules were detected in 10 (12.9%) of 77 patients with PCD: 2 (28.6%) of 7 with WM, 1 (16.6%) of 6 with MGUS, 6 (9.6%) of 62 with MM, and 1 of 2 patients with HCD. Isolated CD55 deficiency was found in 28.5% of all PCD patients, whereas isolated CD59 deficiency was not observed in any patients. These findings illustrate the existence of the PNH phenotype in the red cells of patients with PCD; further investigation is needed into the mechanisms and significance of this phenotype.
Frequent detection of T cells with mutations of the hypoxanthine-guanine phosphoribosyl transferase gene in patients with paroxysmal nocturnal hemoglobinuria. Horikawa K, Kawaguchi T, Ishihara S, Nagakura S, Hidaka M, Kagimoto T, Mitsuya H, Nakakuma H. Second Department of Internal Medicine, Kumamoto University School of Medicine, Japan.	Blood 2002 Jan 1;99(1):24-9 Abstract quote Acquired mutations of the PIG-A gene result in the hemolysis characteristic of paroxysmal nocturnal hemoglobinuria (PNH). Although the etiology of the mutation(s) is unclear, mutable conditions have been suggested by the coexistence of multiple clones with different mutations of PIG-A and by the appearance of leukemic clones in patients with PNH. This study sought to test this hypothesis by examining the frequency of hypoxanthine-guanine phosphoribosyl transferase (HPRT) gene mutations, identified by both resistance to 6-thioguanine (6-TG) and gene analysis. T-cell colonies resistant to 6-TG formed in methylcellulose culture were found in 8 (67%) of 12 PNH patients and 3 (18%) of 17 age-matched healthy volunteers (P <.02, Fisher exact probability test). The incidence of resistant colonies ranged from 40 to 367 (mean 149, x 10(-7)) in the 8 patients and from 1 to 16 (mean 7, x 10(-7)) in the 3 healthy donors. Thus, the HRPT gene mutated more frequently in patients with PNH than in healthy controls (P <.02, Mann-Whitney test). Analysis of bone marrow cells supported these findings. Like the PIG-A mutations in PNH, the HPRT mutations were widely distributed in the coding regions and consisted primarily of base deletions. Unlike PNH cells, 6-TG-resistant cells expressed CD59, indicating that the HPRT mutations did not occur in PNH clones. No correlation was noted between HPRT mutation frequency and content of therapy received by the patients. It is concluded that in PNH patients, conditions exist that favor the occurrence of diverse somatic mutations in blood cells.
PYODERMA GANGRENOSUM
Pyoderma gangrenosum associated with paroxysmal nocturnal hemoglobulinuria and monoclonal gammopathy. Matsubara K, Isoda K, Maeda Y, Mizutani H. Department of Dermatology, Mie University, Faculty of Medicine, Tsu, Japan.	J Dermatol 2002 Feb;29(2):86-90 Abstract quote Pyoderma gangrenosum developed in a man with a five-year history of paroxysmal nocturnal hemoglobinuria and monoclonal gammopathy. He had multiple walnut sized ulcers on his back and extremities, plasma IgM-k type M-protein and low erythrocytic CD55 expression. This is an extremely rare association. However, clonal expansion of plasma cells and chimeric expression of hematopoietic cell glycosylphosphatidylinositol (GPI)-anchored proteins may represent somatic mutations of hematopoietic stem cells in PG as well as PNH. PNH is based on abnormalities in the GPI-anchor formation on various hematopoietic and non-hematopoietic cells. Since the GPI-anchored proteins have pleiotropic functions in complement mediated cell lysis, leukocyte motility, and coagulation systems, the present case may indicate the possible involvement of a GPI-anchored protein abnormality in the pathogenesis of PG.

 

PATHOGENESIS	CHARACTERIZATION
CD95 FAS
Impaired growth and elevated fas receptor expression in PIGA(+) stem cells in primary paroxysmal nocturnal hemoglobinuria. Chen R, Nagarajan S, Prince GM, Maheshwari U, Terstappen LW, Kaplan DR, Gerson SL, Albert JM, Dunn DE, Lazarus HM, Medof ME. Institute of Pathology, Case Western Reserve University, Cleveland, Ohio, USA.	J Clin Invest 2000 Sep;106(5):689-96 Abstract quote The genetic defect underlying paroxysmal nocturnal hemoglobinuria (PNH) has been shown to reside in PIGA, a gene that encodes an element required for the first step in glycophosphatidylinositol anchor assembly. Why PIGA-mutated cells are able to expand in PNH marrow, however, is as yet unclear. To address this question, we compared the growth of affected CD59(-)CD34(+) and unaffected CD59(+)CD34(+) cells from patients with that of normal CD59(+)CD34(+) cells in liquid culture. One hundred FACS-sorted cells were added per well into microtiter plates, and after 11 days at 37 degrees C the progeny were counted and were analyzed for their differentiation pattern. We found that CD59(-)CD34(+) cells from PNH patients proliferated to levels approaching those of normal cells, but that CD59(+)CD34(+) cells from the patients gave rise to 20- to 140-fold fewer cells. Prior to sorting, the patients' CD59(-) and CD59(+)CD34(+) cells were equivalent with respect to early differentiation markers, and following culture, the CD45 differentiation patterns were identical to those of control CD34(+) cells. Further analyses of the unsorted CD59(+)CD34(+) population, however, showed elevated levels of Fas receptor. Addition of agonist anti-Fas mAb to cultures reduced the CD59(+)CD34(+) cell yield by up to 78% but had a minimal effect on the CD59(-)CD34(+) cells, whereas antagonist anti-Fas mAb enhanced the yield by up to 250%. These results suggest that expansion of PIGA-mutated cells in PNH marrow is due to a growth defect in nonmutated cells, and that greater susceptibility to apoptosis is one factor involved in the growth impairment.
CHROMOSOMAL ABNORMALITIES
Cytogenetic and morphological abnormalities in paroxysmal nocturnal haemoglobinuria. Araten DJ, Swirsky D, Karadimitris A, Notaro R, Nafa K, Bessler M, Thaler HT, Castro-Malaspina H, Childs BH, Boulad F, Weiss M, Anagnostopoulos N, Kutlar A, Savage DG, Maziarz RT, Jhanwar S, Luzzatto L. Department of Human Genetics, Memorial Sloan-Kettering Cancer Center, New York, USA.	Br J Haematol 2001 Nov;115(2):360-8 Abstract quote Paroxysmal nocturnal haemoglobinuria (PNH) is characterized by the expansion of a haematopoietic stem cell clone with a PIG-A mutation (the PNH clone) in an environment in which normal stem cells are lost or failing: it has been hypothesized that this abnormal marrow environment provides a relative advantage to the PNH clone. In patients with PNH, generally, the karyotype of bone marrow cells has been reported to be normal, unlike in myelodysplastic syndrome (MDS), another clonal condition in which cytogenetic abnormalities are regarded as diagnostic. In a retrospective review of 46 patients with a PNH clone, we found a karyotypic abnormality in 11 (24%). Upon follow-up, the proportion of cells with abnormal karyotype decreased significantly in seven of these 11 patients. Abnormal morphological bone marrow features reminiscent of MDS were common in PNH, regardless of the karyotype. However, none of our patients developed excess blasts or leukaemia. We conclude that in patients with PNH cytogenetically abnormal clones are not necessarily malignant and may not be predictive of evolution to leukaemia.
MEMBRANE DEFECTS OF GPI (GLYCOSYLPHOSPHATIDYL INOSITOL)
Paroxysmal nocturnal hemoglobinuria: molecular pathogenesis and molecular therapeutic approaches. Nishimura J, Smith CA, Phillips KL, Ware RE, Rosse WF. Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA.	Hematopathol Mol Hematol 1998;11(3-4):119-46 Abstract quote Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal hematologic stem cell disorder classified as an intravascular hemolytic anemia. Abnormal blood cells are deficient in glycosylphosphatidyl inositol (GPI)-anchored proteins. Deficiencies of GPI-anchored complement regulatory proteins, such as decay accelerating factor (DAF) and CD59, render red cells very sensitive to complement and result in complement-mediated hemolysis and hemoglobinuria. In the affected hematopoietic cells from patients with PNH, the first step in biosynthesis of the GPI anchor is defective. Three genes are involved in this reaction step and one of them, an X-linked gene termed PIG-A, is mutated in affected cells. Granulocytes and lymphocytes from the same patient have the same mutation, indicating that a somatic PIG-A mutation occurs in hematopoietic stem cells. The PIG-A gene is mutated in all patients with PNH reported to date. We review these recent advances in the understanding of the molecular pathogenesis of PNH. Furthermore, we present an hypothesis regarding the predominance of the PNH clone, caused by positive selection by hematopoietic suppressive cytokines, such as transforming growth factor (TGF)-beta. In addition, we discuss the possibility of cure for PNH through molecular therapeutic strategy using gene transfer techniques.
Role of decay-accelerating factor in regulating complement activation on the erythrocyte surface as revealed by gene targeting. Sun X, Funk CD, Deng C, Sahu A, Lambris JD, Song WC. Center for Experimental Therapeutics and Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.	Proc Natl Acad Sci U S A 1999 Jan 19;96(2):628-33 Abstract quote Decay-accelerating factor (DAF) is a glycosylphosphatidylinositol (GPI)-anchored membrane protein that inhibits both the classical and the alternative pathways of complement activation. DAF has been studied extensively in humans under two clinical settings: when absent from the erythrocytes of paroxysmal nocturnal hemoglobinuria (PNH) patients, who suffer from complement-mediated hemolytic anemia, and in transgenic pigs expressing human DAF, which have been developed to help overcome complement-mediated hyperacute rejection in xenotransplantation. Nevertheless, the exact role of DAF in regulating complement activation in vivo on the cell surface and the species specificity of this molecule remain to be fully characterized. To address these issues, we have used gene targeting to produce mice lacking GPI-anchored DAF. We found that erythrocytes from mice deficient in GPI-anchored DAF showed no increase in spontaneous complement activation in vivo but exhibited impaired regulation of zymosan-initiated bystander and antibody-triggered classical pathway complement activation in vitro, resulting in enhanced complement deposition. Despite a high level of C3 fixation, no homologous hemolysis occurred. It is noteworthy that GPI-linked DAF knockout erythrocytes, when tested with human and guinea pig sera, were more susceptible to heterologous complement lysis than were normal erythrocytes. These results suggest that DAF is capable of regulating homologous as well as heterologous complement activation via the alternative or the classical pathway. They also indicate that DAF deficiency alone is not sufficient to cause homologous hemolysis. In contrast, when the assembly of the membrane-attack complex is not properly regulated, as in the case of heterologous complement activation or in PNH patients, impaired erythrocyte DAF activity and enhanced C3 deposition could lead to increased hemolytic reaction.
Clonal populations of hematopoietic cells with paroxysmal nocturnal hemoglobinuria genotype and phenotype are present in normal individuals. Araten DJ, Nafa K, Pakdeesuwan K, Luzzatto L. Department of Human Genetics, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10021, USA.	Proc Natl Acad Sci U S A 1999 Apr 27;96(9):5209-14 Abstract quote In paroxysmal nocturnal hemoglobinuria (PNH), acquired somatic mutations in the PIG-A gene give rise to clonal populations of red blood cells unable to express proteins linked to the membrane by a glycosylphosphatidylinositol anchor. These proteins include the complement inhibitors CD55 and CD59, and this explains the hypersensitivity to complement of red cells in PNH patients, manifested by intravascular hemolysis. The factors that determine to what extent mutant clones expand have not yet been pinpointed; it has been suggested that existing PNH clones may have a conditional growth advantage depending on some factor (e.g., autoimmune) present in the marrow environment of PNH patients. Using flow cytometric analysis of granulocytes, we now have identified cells that have the PNH phenotype, at an average frequency of 22 per million (range 10-51 per million) in nine normal individuals. These rare cells were collected by flow sorting, and exons 2 and 6 of the PIG-A gene were amplified by nested PCR. We found PIG-A mutations in six cases: four missense, one frameshift, and one nonsense mutation. PNH red blood cells also were identified at a frequency of eight per million. Thus, small clones with PIG-A mutations exist commonly in normal individuals, showing clearly that PIG-A gene mutations are not sufficient for the development of PNH. Because PIG-A encodes an enzyme essential for the expression of a host of surface proteins, the PIG-A gene provides a highly sensitive system for the study of somatic mutations in hematopoietic cells.
Glycosyl phosphatidylinositol (GPI)-anchored molecules and the pathogenesis of paroxysmal nocturnal hemoglobinuria. Boccuni P, Del Vecchio L, Di Noto R, Rotoli B. Servizio di Immunoematologia, Ospedale Cardarelli, Napoli, Italy.	Crit Rev Oncol Hematol 2000 Jan;33(1):25-43 Abstract quote 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.
Paroxysmal nocturnal hemoglobinuria: insights from recent advances in molecular biology. Bessler M, Schaefer A, Keller P. Division of Hematology, Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA.	Transfus Med Rev 2001 Oct;15(4):255-67Abstract quote Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, acquired hemolytic anemia characterized by the increased sensitivity of red cells to complement, leading to intravascular hemolysis and hemoglobinuria. Other clinical features are cytopenias caused by bone marrow failure and an increased risk of thrombosis. If unrecognized and not treated appropriately, PNH is often associated with a substantial morbidity and mortality. PNH is caused by the expansion of a hematopoietic progenitor cell that caries a somatic mutation in the X-linked phosphatidylinositol glycan complementation group A (PIGA) gene. The PIGA gene encodes a protein essential in the biosynthesis of glycosylphosphatidylinositol (GPI)-anchor molecules. A proportion of blood cells from patients with PNH is therefore deficient in all GPI-linked surface proteins. Considerable progress in the field of PNH research in the last 7 years has resulted from the cloning of the PIGA gene. The purpose of the current article is to describe the structure and function of the PIGA gene, to summarize the lessons learned from the analysis of PIGA gene mutations, to review the impact of mouse models on our current understanding of the human disease, and to discuss the possible pathogenesis of PNH. In addition, we will outline novel approaches to PNH diagnosis, research, and therapy that became available thanks to the cloning of the PIGA gene.
Targeted deletion of the CD59 gene causes spontaneous intravascular hemolysis and hemoglobinuria. Holt DS, Botto M, Bygrave AE, Hanna SM, Walport MJ, Morgan BP. Complement Biology Group, Department of Medical Biochemistry, University of Wales College of Medicine, Cardiff, United Kingdom	Blood 2001 Jul 15;98(2):442-9 Abstract quote The glycolipid-anchored glycoprotein CD59 inhibits assembly of the lytic membrane attack complex of complement by incorporation into the forming complex. Absence of CD59 and other glycolipid-anchored molecules on circulating cells in the human hemolytic disorder paroxysmal nocturnal hemoglobinuria is associated with intravascular hemolysis and thrombosis. To examine the role of CD59 in protecting host tissues in health and disease, CD59-deficient (CD59(-/-)) mice were produced by gene targeting in embryonic stem cells. Absence of CD59 was confirmed by staining cells and tissues with specific antibody. Despite the complete absence of CD59, mice were healthy and fertile. Erythrocytes in vitro displayed increased susceptibility to complement and were positive in an acidified serum lysis test. Despite this, CD59(-/-) mice were not anemic but had elevated reticulocyte counts, indicating accelerated erythrocyte turnover. Fresh plasma and urine from CD59(-/-) mice contained increased amounts of hemoglobin when compared with littermate controls, providing further evidence for spontaneous intravascular hemolysis. Intravascular hemolysis was increased following administration of cobra venom factor to trigger complement activation. CD59(-/-) mice will provide a tool for characterizing the importance of CD59 in protection of self tissues from membrane attack complex damage in health and during diseases in which complement is activated.
Paroxysmal nocturnal hemoglobinuria: Differential gene expression of EGR-1 and TAXREB107. Lyakisheva A, Felda O, Ganser A, Schmidt RE, Schubert J. Dept. of Hematology/Oncology, Hannover Medical School, Hannover, Germany.	Exp Hematol 2002 Jan;30(1):18-25 Abstract quote OBJECTIVE: Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal defect of hematopoietic stem cells characterized by deficiency in GPI-anchored surface proteins. It is not yet known how GPI-deficient stem cells are able to expand within the bone marrow and contribute considerably to the hematopoiesis. In PNH, as well as in AA and MDS, genetic instability and increased mutation frequency have been detected. Therefore, a second event is very likely, such as additional mutations, leading to clonal expansion of GPI-deficient bone marrow stem cell in PNH. METHODS: In order to elucidate the molecular basis of clonal expansion in PNH, we identified several genes differentially expressed in normal and GPI-deficient cells of PNH patients by combination of RNA fingerprinting and cDNA array hybridization. RESULTS: Expression of two of these genes, EGR-1 and TAXREB107, has been further investigated. EGR-1 is upregulated in granulocytes of all PNH patients analyzed so far. In contrast, significant upregulation of TAXREB107 is present only in some of our PNH patients. Further analysis confirmed their overexpression in PNH and excluded a possible secondary event character of observed overexpression. Moreover, similar levels of expression in cases of other clonal diseases, such as MPS and MDS, has been identified. CONCLUSION: Our data suggest that additional genetic alterations apart from PIG-A mutations could be present in PNH granulocytes. In addition, these genetic changes might contribute to clonal expansion of GPI-deficient cells in PNH.
Granulocytes from patients with paroxysmal nocturnal hemoglobinuria and normal individuals have the same sensitivity to spontaneous apoptosis. Yamamoto T, Shichishima T, Shikama Y, Saitoh Y, Ogawa K, Maruyama Y. First Department of Internal Medicine, Fukushima Medical University, Fukushima, Japan.	Exp Hematol 2002 Mar;30(3):187-94 Abstract quote OBJECTIVE: The aim of this study was to determine whether granulocytes from patients with paroxysmal nocturnal hemoglobinuria (PNH) are more or less intrinsically sensitive to spontaneous apoptosis than granulocytes from healthy individuals. Resistance to apoptosis has been suggested as an explanation for the proliferation or selection of PNH clones. PATIENTS AND METHODS: Peripheral blood granulocytes from five patients with PNH, five patients with myelodysplastic syndrome (MDS), and five healthy volunteers were cultured in the absence of serum. Spontaneous apoptosis of the granulocytes was assessed every 6 hours by flow cytometry. The expression levels of CD16b, CD95, and granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor also were studied by flow cytometry, and caspase-3 activity was measured by fluorometry. RESULTS: There were no significant differences in the proportion or absolute numbers of apoptotic and apoptotic/dead granulocytes between the cells from PNH patients and healthy individuals, whereas those from MDS patients showed significantly lower frequencies of apoptotic granulocytes compared with normal controls. The proportion of CD16b(-) granulocytes was not significantly different among the three groups during in vitro culture. CD95 and GM-CSF receptor was not significantly increased in cultured granulocytes or noncultured granulocytes from, respectively, patients with PNH and normal controls. Caspase-3 activity significantly decreased in cultured granulocytes from MDS patients, but not in granulocytes from PNH patients. CONCLUSIONS: Granulocytes from PNH patients did not display a reduced sensitivity to spontaneous apoptosis, suggesting that the apoptosis of blood cells in PNH may not be an important factor in proliferation or selection of PNH clones. These findings are in agreement with the normal lifespan of granulocytes in vivo.
Crry, but not CD59 and DAF, is indispensable for murine erythrocyte protection in vivo from spontaneous complement attack. Miwa T, Zhou L, Hilliard B, Molina H, Song WC. Center for Experimental Therapeutics and Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia 19104, USA.	Blood 2002 May 15;99(10):3707-16 Abstract quote Decay-accelerating factor (DAF) and CD59 are 2 glycosylphosphatidylinositol-anchored membrane proteins that inhibit complement activation at the C3 and C5b-9 step, respectively. CD59 is considered critical for protecting erythrocytes from spontaneous complement attack, as deficiency of CD59 or CD59/DAF, but not of DAF alone, on human erythrocytes renders them sensitive to complement lysis in paroxysmal nocturnal hemoglobinuria syndrome. To evaluate the relative roles of CD59 and DAF in vivo, we have generated and studied a CD59 knockout and a CD59/DAF double-knockout mouse. CD59-deficient and CD59/DAF-double-deficient mouse erythrocytes were highly sensitive to antibody-induced complement lysis in vitro, yet neither CD59 knockout nor CD59/DAF double-knockout mouse developed spontaneous hemolytic anemia. Consistent with the latter observation, erythrocytes from the 2 strains of mutant mice were shown to have a normal lifespan in vivo. In contrast, mouse erythrocytes deficient in complement receptor 1 (CR1)-related gene y (Crry), a membrane C3 inhibitor with DAF and membrane cofactor protein activities, were rapidly eliminated from the circulation by a complement-dependent mechanism. Compared with DAF-deficient erythrocytes, Crry-deficient erythrocytes incurred higher levels of spontaneous C3 deposition in vivo. These findings demonstrate that CD59 and DAF are not indispensable on murine erythrocytes. Rather, effective C3 regulation on the cell surface, provided by Crry rather than DAF, is necessary for mouse erythrocytes to resist spontaneous complement attack. Our results raise the possibility that proper control of C3 activation may also be critical on human erythrocytes, where CR1 but not DAF could be the principal regulator of spontaneous C3 activation.

 

LABORATORY/RADIOLOGIC/ OTHER TESTS	CHARACTERIZATION
LABORATORY MARKERS
SUCROSE HEMOLYSIS TEST	Sucrose provides a medium of low ionic strength that promotes binding of complement to the red cells, leading to enhanced complement mediated lysis
HAM TEST (ACIDIFIED SERUM TEST)	Complement is activated by the alternative complement pathway, leading to lysing of the red cells
CD55 AND CD59
Diagnosis of paroxysmal nocturnal haemoglobinuria by phenotypic analysis of erythrocytes using two-colour flow cytometry with monoclonal antibodies to DAF and CD59/MACIF. Shichishima T, Terasawa T, Saitoh Y, Hashimoto C, Ohto H, Maruyama Y. First Department of Internal Medicine, Fukushima Medical College, Japan.	Br J Haematol 1993 Oct;85(2):378-86 Abstract quote We investigated the relationship between the complement lysis sensitivity test and two-colour flow cytometric analysis using monoclonal antibodies to decay accelerating factor (DAF) and CD59/membrane attack complex inhibitory factor (MACIF) in patients with paroxysmal nocturnal haemoglobinuria (PNH) and other haematological diseases. Flow cytometry showed that all 59 PNH patients had two or three erythrocyte populations, while all 74 patients with other haematological diseases and all 31 healthy volunteers had a single erythrocyte population. We compared the percentage of PNH III erythrocytes in the lysis test with the percentage of negative cells shown by flow cytometry in 52 PNH patients, and found a significant correlation (r = 0.960, P < 0.001). However, in 13 patients the erythrocyte phenotypes did not correspond in both tests. This was generally related to difficulty of detecting PNH II erythrocytes in the lysis test. In the PNH patients the ranges of mean fluorescence intensity for the negative, intermediate and positive erythrocyte populations were respectively 1.1-2.5, 2.2-29, and 61-600 for CD59/MACIF positivity and 1.9-7.2, 3.6-22. and 31-350 for DAF positivity. In contrast, the mean intensities in healthy volunteers ranged from 190 to 720 for CD59/MACIF and from 150 to 350 for DAF. These findings suggest that PNH can be diagnosed and phenotypic analysis of PNH erythrocytes can be performed by respectively assessing the fluorescence profiles and mean fluorescence intensities of both proteins using flow cytometry. Flow cytometry may provide a superior diagnostic method to the traditional tests for PNH.
Application of flow cytometry to the diagnosis of paroxysmal nocturnal hemoglobinuria. Richards SJ, Rawstron AC, Hillmen P. Hematological Malignancy Diagnostic Service, Department of Hematology, Leeds General Infirmary, Leeds, United Kingdom.	Cytometry 2000 Aug 15;42(4):223-33 Abstract quote Within the contemporary multitude of complex methods used in clinical flow cytometry, very few techniques exist which can be described as disease-specific diagnostic tests. Detection of glycophosphatidylinositol (GPI)-linked antigens on hematopoietic cells using monoclonal antibodies and flow cytometry forms the basis of a specific diagnostic test for paroxysmal nocturnal hemoglobinuria (PNH). Absent or markedly diminished expression of GPI-linked antigens is, in the appropriate clinical setting, specific for all patients with PNH. Clinically, PNH is a syndrome characterized by bone marrow failure, acquired hemolytic anemia, and a thrombotic tendency. The molecular genetic lesion responsible for this condition is a somatic mutation of the X-linked pig-a gene within a multipotent hematopoietic stem cell. Due to its rarity, delay in diagnosis is not uncommon for patients with PNH. Once a definitive diagnosis is established, this can make a considerable impact on patient management and prognosis. In this article, we review the complimentary roles that molecular biology and flow cytometry have played in unraveling the genotypic and phenotypic aspects of this unique condition.
A standardized flow cytometric method for screening paroxysmal nocturnal haemoglobinuria (PNH) measuring CD55 and CD59 expression on erythrocytes and granulocytes. Oelschlaegel U, Besson I, Arnoulet C, Sainty D, Nowak R, Naumann R, Bux Y, Ehninger G. Medical Clinic and Policlinic I, University Hospital Dresden, Haus 66a, Fetscherstrasse 74, 01307 Dresden, Germany.	Clin Lab Haematol 2001 Apr;23(2):81-90 Abstract quote PNH is a disorder of the pluripotent stem cells resulting in a deficient expression of membrane-bound GPI-anchored proteins in different cell types. Several flow cytometric approaches are designed to detect this antigen deficiency. But they all require drawing and testing of normal samples as control. Therefore, in the present study two flow cytometric assays for the detection of CD55 and CD59 deficiency in erythrocytes (REDQUANT CD55/CD59) and granulocytes (CELLQUANT CD55/CD59) are proposed. Precalibrated beads are used to define the cut off between normal and deficient cell populations. The specificity of the tests has been evaluated in healthy blood donors (n=52) resulting in a clear and reproducible cut off (3%) for the normal percentage of GPI-deficient cells. This cut off has been confirmed in leukaemia and lymphoma patients not suspected for developing PNH. The sensitivity has been tested in patients suffering from known PNH (n=23). Both tests performed in combination allowed a reliable detection of PNH in all patients showing antigen deficiencies in both cell types in most patients (20/23). In contrast, the PNH clones in the investigated patients with MDS (4/19) or AA (4/22) were present in granulocytes or erythrocytes, only. This underlines the necessity of analysing erythrocytes as well as granulocytes. Preliminary data regarding a possible correlation between disease activity and percentage of antigen-deficient cells lead to the assumption that haemolytic crises can only be determined on granulocytes whereas deficient erythrocytes disappeared due to complement-mediated lysis of the PNH clone. In conclusion, the combination of the test kits enables the differential diagnosis of PNH clones in a standardized, simple and rapid approach which may have therapeutic consequences.

 

GROSS APPEARANCE/ CLINICAL VARIANTS	CHARACTERIZATION
GENERAL
VARIANTS
GASTROINTESTINAL TRACT
Gastrointestinal involvement in paroxysmal nocturnal hemoglobinuria: first report of electron microscopic findings. Adams T, Fleischer D, Marino G, Rusnock E, Li L. Department of Internal Medicine, Georgetown University Medical Center, Washington, District of Columbia 20007, USA.	Dig Dis Sci 2002 Jan;47(1):58-64 Abstract quote Thrombotic complications, particularly microthrombi involving intraabdominal veins leading to intestinal ischemia, have remained a major cause of morbidity in patients with paroxysmal nocturnal hemoglobinuria (PNH). While intestinal ischemia has been postulated to be the cause of recurrent bouts of abdominal pain in this population, direct antemortem evidence for this complication is scarcely documented in the literature. We describe a case of PNH in a patient who presented with abdominal distress three years after the initial diagnosis was established. Clinical features and a combination of diagnostic modalities, including radiography, endoscopy, and histology were used to make the prompt diagnosis of intestinal ischemia. This is the first case in which the electronic microscopy of the gastrointestinal lesion is described. Our patient was successfully treated with conservative measures and anticoagulation.

PROGNOSIS AND TREATMENT	CHARACTERIZATION
PROGNOSTIC FACTORS
Natural history of paroxysmal nocturnal hemoglobinuria. Hillmen P, Lewis SM, Bessler M, Luzzatto L, Dacie JV. Department of Haematology, Royal Postgraduate Medical School, London, United Kingdom.	N Engl J Med 1995 Nov 9;333(19):1253-8 Abstract quote 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.
Aplastic anemia and paroxysmal nocturnal hemoglobinuria: a follow-up study of the glycosylphosphatidylinositol-anchored proteins defect. Noguera ME, Leymarie V, Bittencourt E, Gluckman E, Sigaux F, Socie G. Laboratoire Central d'Hematologie, Hopital Saint-Louis, Paris, France.	Hematol J 2000;1(4):250-3 Abstract quote INTRODUCTION:: Flow cytometry analysis of peripheral blood cells is a simple and reliable method for establishing the diagnosis of paroxysmal nocturnal hemoglobinuria. The behavior of the clone may vary; increasing or diminishing over time but prospective study of such variations have not been reported so far. MATERIALS AND METHODS:: We report herein the results of a prospective follow-up study of 25 patients. Our aims were twofold: first, to evaluate the behavior of the clone (using flow cytometry) over the time; and second, to evaluate if such variations could predict the occurrence of complications or could be used as a tool for monitoring the residual disease after bone marrow transplantation. RESULTS:: It was found that flow cytometry can be used to specifically follow the residual disease post allogeneic marrow transplantation in four patients, and that even without transplantation the defective clone can significantly decrease or even disappear (three patients). CONCLUSION:: We found that most of the patients did have significant change in the amount of affected cells during more than three years, and that an increased size of the clone poorly predicted the occurrence of complications.
Long-term support of hematopoiesis by a single stem cell clone in patients with paroxysmal nocturnal hemoglobinuria. Nishimura Ji J, Hirota T, Kanakura Y, Machii T, Kageyama T, Doi S, Wada H, Masaoka T, Kanayama Y, Fujii H, Inoue N, Kuwayama M, Inoue N, Ohishi K, Kinoshita T. Department of Immunoregulation/Research Institute for Microbial Diseases and the Research Foundation for Microbial Diseases, Osaka University, Japan.	Blood 2002 Apr 15;99(8):2748-51 Abstract quote Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired hematopoietic stem cell disorder characterized by clonal blood cells that are deficient in glycosylphosphatidylinositol-anchored proteins because of somatic mutations of the PIG-A gene. Many patients with PNH have more than one PNH clone, but it is unclear whether a single PNH clone remains dominant or minor clones eventually become dominant. Furthermore, it is unknown how many hematopoietic stem cells (HSCs) sustain hematopoiesis and how long a single HSC can support hematopoiesis in humans. To understand dynamics of HSCs, we reanalyzed the PIG-A gene mutations in 9 patients 6 to 10 years after the previous analyses. The proportion of affected peripheral blood polymorphonuclear cells (PMNs) in each patient was highly variable; it increased in 2 (from 50% and 65% to 98% and 97%, respectively), was stable in 4 (changed less than 20%), and diminished in 3 (94%, 99%, and 98% to 33%, 57%, and 43%, respectively) patients. The complexity of these results reflects the high variability of the clinical course of PNH. In all patients, the previously predominant clone was still present and dominant. Therefore, one stem cell clone can sustain hematopoiesis for 6 to 10 years in patients with PNH. Two patients whose affected PMNs decreased because of a decline of the predominant PNH clone and who have been followed up for 24 and 31 years now have an aplastic condition, suggesting that aplasia is a terminal feature of PNH.
TREATMENT
BONE MARROW TRANSPLANT
Bone marrow transplants for paroxysmal nocturnal haemoglobinuria. Saso R, Marsh J, Cevreska L, Szer J, Gale RP, Rowlings PA, Passweg JR, Nugent ML, Luzzatto L, Horowitz MM, Gordon-Smith EC. Department of Haematology, St George's Hospital Medical School, London, UK.	Br J Haematol 1999 Feb;104(2):392-6 Abstract quote Paroxysmal nocturnal haemoglobinuria (PNH) is a rare clonal haematological disorder characterized by intravascular haemolysis and increased risk of thrombosis. PNH is associated with bone marrow failure syndromes including aplastic anaemia, myelodysplasia and leukaemia. Bone marrow transplants are sometimes used to treat PNH, but small series and reporting biases make assessment of transplant outcome difficult. The outcome of 57 consecutive allogeneic bone marrow transplants for PNH reported to the International Bone Marrow Transplant Registry (IBMTR) between 1978 and 1995 was analysed. The 2-year probability of survival in 48 recipients of HLA-identical sibling transplants was 56% (95% confidence interval 49-63%). Two recipients of identical twin transplants remain alive 8 and 12 years after treatment. One of seven recipients of alternative donor allogeneic transplants is alive 5 years after transplant. The most common causes of treatment failure were graft failure and infections. Our results indicate that bone marrow transplantation can restore normal bone marrow function in about 50% of PNH patients.
Successful unrelated donor bone marrow transplantation for paroxysmal nocturnal hemoglobinuria. Woodard P, Wang W, Pitts N, Benaim E, Horwitz E, Cunningham J, Bowman L. Division of Bone Marrow Transplantation, Department of Hematology/Oncology, St Jude Children's Research Hospital, Memphis, TN 38105-2794, USA.	Bone Marrow Transplant 2001 Mar;27(6):589-92 Abstract quote Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal disease of hematopoiesis due to a mutation in the PIG-A gene. Affected patients may demonstrate hemolysis or venous thrombosis, and may develop MDS or aplastic anemia. Successful results may be obtained after conditioning and transplantation from syngeneic or genotypically matched sibling donors. Experience with transplantation from matched unrelated donors (MUD) is limited to eight patients, with only one survivor. We report three patients who underwent successful MUD BMT for PNH. All three patients had severe aplastic anemia (SAA) and PNH at the time of BMT. Unrelated donors were six-antigen HLA-matched (n = 2) or HLA-A mismatched (n = 1). Conditioning consisted of cytarabine, cyclophosphamide, TBI, and ATG. Grafts were T cell-depleted by anti-CD6/CD8 antibodies + complement. Further GVHD prophylaxis consisted of cyclosporine. Patients received 0.7-1.1 x 10(8) nucleated cells/kg and 1.1-2.1 x 10(6) CD34(+) cells/kg. Neutrophil engraftment occurred at 16-21 days. One patient developed grade 1 acute GVHD. Although all three patients experienced significant transplant-related complications, they ultimately resolved and all patients are alive and well 30-62 months after BMT. T cell-depleted MUD BMT is an effective treatment option for PNH-related MDS and SAA.
DANAZOL
Monitoring of CD59 expression in paroxysmal nocturnal hemoglobinuria treated with danazol. Katayama Y, Hiramatsu Y, Kohriyama K. Department of Internal Medicine, Kobe West City Hospital, Kobe, Japan	Am J Hematol 2001 Dec;68(4):280-3 Abstract quote We describe a 52-year-old man with paroxysmal nocturnal hemoglobinuria (PNH) and a moderate transfusion requirement. Prior to and during sequential therapy with androgen (metenolone), glucocorticoid, and danazol, we evaluated CD59-negative expression (PNH clone) in red blood cells, neutrophils, lymphocyte subsets, and bone marrow (BM) CD34(+) cells. Although androgen and glucocorticoid were not effective for recovery of blood cell counts, the hemoglobin and platelet levels increased immediately after the therapy with danazol and the patient became transfusion independent. However, neither the serum level of LDH nor the percentage of PNH clone in each cell lineage, including BM CD34(+) cells, decreased. The number of nucleated cells in BM increased drastically after the start of danazol. These findings suggest that the efficacy of danazol was not only due to the impediment of hemolysis but also due to stimulation of PNH clone proliferation in BM.
STEM CELL TRANSPLANT
Successful application of nonmyeloablative transplantation for paroxysmal nocturnal hemoglobinuria. Suenaga K, Kanda Y, Niiya H, Nakai K, Saito T, Saito A, Ohnishi M, Takeuchi T, Tanosaki R, Makimoto A, Miyawaki S, Ohnishi T, Kanai S, Tobinai K, Takaue Y, Mineishi S. Stem Cell Transplant Unit, National Cancer Center Hospital, Tokyo, Japan.	Exp Hematol 2001 May;29(5):639-42 Abstract quote OBJECTIVE: Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal hematopoietic stem cell disorder that manifests as hemolytic anemia, venous thrombosis, and deficient hematopoiesis. Although allogeneic hematopoietic stem cell transplantation is considered the only curative therapeutic measure, transplant-related mortality is not negligible. Several studies supported the use of nonmyeloablative stem cell transplantation (NST) for patients of advanced age or with organ dysfunction. Hence, we used NST in a PNH patient who suffered from acute renal failure due to repeated episodes of hemolysis. MATERIALS AND METHODS: We performed NST using a conditioning regimen consisting of cladribine 0.11 mg/kg x 6, busulfan 4 mg/kg x 2, and rabbit anti-thymocyte globulin 2.5 mg/kg x 2. He received peripheral blood stem cells from his human leukocyte antigen-matched brother. Prophylaxis against graft-vs-host disease was performed with cyclosporine A alone. Chimerism of peripheral blood mononuclear cells was evaluated serially using short tandem repeat analysis and flow cytometry. RESULTS: No meaningful regimen-related toxicities were documented. Donor chimerism of 90 to 100% was achieved on day 14 and thereafter. The patient is doing well, without any recurrence of hemolysis 6 months after transplant. Follow-up chimerism studies confirmed stable and functioning donor-type hematopoiesis. CONCLUSIONS: NST may become a safe and curative approach in patients with PNH. Further studies are needed to establish the role of NST for treatment of PNH.
Conditioning with high-dose cyclophosphamide may not be sufficient to provide a long-term remission of paroxysmal nocturnal hemoglobinuria following syngeneic peripheral blood stem cell transplantation. Cho SG, Lim J, Kim Y, Eom HS, Jin CY, Han CW, Kim CC. Catholic Hematopoietic Stem Cell Transplantation Center, College of Medicine, The Catholic University of Korea, Seoul, Korea.	Bone Marrow Transplant 2001 Nov;28(10):987-8 Abstract quote A patient with paroxysmal nocturnal hemoglobinuria (PNH) received a syngeneic peripheral blood stem cell transplant (PBSCT) with high-dose cyclophosphamide (CY) conditioning. He had a reasonable engraftment and complete hematologic recovery. However, at 12 months after PBSCT, he became symptomatic and peripheral blood cells were almost entirely composed of glycosylphosphatidylinositol-anchored proteins deficient cells. This case suggests that high-dose CY may not exert a significant effect on PNH clones in the long term, although it had been effective in allogeneic BMT. In view of the possible autoimmune basis, it seems to be necessary to include other immunosuppressive therapy including ALG in addition to CY.
TRANSFER OF GPI
Correction of the PNH defect by GPI-anchored protein transfer. Sloand EM, Maciejewski JP, Dunn D, Moss J, Brewer B, Kirby M, Young NS. Hematology Branch, Pulmonary Critical Care Medicine Branch, and Molecular Disease Branch, National Heart, Lung, and Blood Institute, Bethesda, MD, USA.	Blood 1998 Dec 1;92(11):4439-45 Abstract quote Hemolytic anemia is a major feature of paroxysmal nocturnal hemoglobinuria (PNH). Intravascular red blood cell (RBC) destruction is caused by increased sensitivity of the abnormal erythrocyte to complement-mediated lysis, due to the GPI absence of a membrane-bound glycosylphosphatidylinositol (GPI)-linked protein, which functions as an inhibitor of reactive lysis (CD59). Both in vivo and in vitro models have suggested the feasibility of cell-to-cell transfer of GPI proteins, and patients with hemolysis could potentially benefit from transfer of CD59 to their deficient erythrocytes. We studied the ability of RBC components prepared from outdated packed RBC collections, as well as high-density lipoprotein (HDL) preparations, rich in CD55 and CD59, to promote protein transfer, as assessed by flow cytometry, immunoblotting, and susceptibility to complement-mediated lysis. By flow cytometry, CD55 and CD59 were present on RBC-derived microvesicles that stained with an antiglycophorin antibody Ab; in addition, soluble CD59 and CD55 were detected by immunoblot in soluble fractions eluated from RBC units stored for more than 35 days, but not in fresh blood. Both commercial HDL preparations and those prepared in our laboratory contained CD55 and CD59, as assayed by immunoblot. When RBC that were deficient (GPI)-anchored protein, obtained from five patients, with PNH were incubated with HDL preparations for 2 to 4 hours, there was significant transfer of both proteins to the cell surface, as demonstrated by flow cytometry. Washed RBC microvesicles, prepared by ultrasonification, also mediated transfer of GPI-linked proteins to deficient RBC. Pretreatment of microvesicles, RBC eluate preparations, and HDL with phosphatidylinositol-specific, phospholipase C, abrogated protein transfer to deficient cells, indicating that increased cell-associated CD55 and CD59 levels were related to insertion of the intact GPI moiety, rather than to simple adhesion. PNH RBC that were exposed to HDL, RBC eluate preparations, or microvesicles demonstrated decreased in vitro complement-mediated hemolysis in the Ham test. Transfer of GPI-linked proteins from soluble preparations containing CD55 and CD59 to PNH erythrocytes is feasible and may have clinical utility.

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