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PubMed1988

Periodontal surgery for a patient with paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is an uncommon blood stem cell disorder. The acquired defect is in the cell membrane of the precursor of the affected clone, which renders erythrocytes, platelets and granulocytes unusually sensitive to the hemolytic effects of complement. It is characterized by chronic hemolysis, intermittent hemoglobinuria, thrombotic events and bone marrow hypoplasia. Hemolysis is precipitated by infection, strenuous exercise, surgery or menstruation. The dilemma of managing a PNH patient is that both the periodontal infection and the surgical treatment are precipitating factors. Management is further complicated by the fact that the patient is receiving corticosteroids. The treatment of the PNH patient is complex and potentially hazardous. It requires close cooperation between the periodontist and the hematologist. This paper describes the management of one such case.

Adult↗

PubMed1997

Danazol for paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare clonal stem-cell disorder in which blood cells lack complement inhibiting membrane proteins, and become susceptible to complement-mediated injury, leading to chronic intravascular hemolysis and pancytopenia. Glucocorticoids have been a mainstay of therapy. For patients refractory to glucocorticoids and requiring blood transfusions, an alternative therapy is needed. We studied danazol therapy in 5 patients refractory to other treatments. Four of the 5 benefited, showing rise in hematocrit and eventual cessation of transfusion requirements. Remissions lasted > or =2 years in 3 and 10 years in 1 patient. Danazol was well-tolerated without serious side effects. Danazol appears to be a good alternative treatment in PNH.

Adolescent↗

PubMed2004

Paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal stem cell disorder resulting from a somatic mutation in the hematopoietic stem cell. It is characterized by intravascular hemolysis, cytopenias, frequent infections, bone marrow hypoplasia, and a high incidence of life-threatening venous thrombosis. An absent glycosylphosphatidylinositol (GPI)-anchored receptor prevents several proteins from binding to the erythrocyte membrane. These include the complement-regulatory proteins, CD55 and CD59, whose absence results in enhanced complement-mediated lysis. Patients present with anemia and hemoglobinuria. Laboratory diagnosis includes the sucrose hemolysis test, Ham acid hemolysis test, and fluorescent-activated cell analysis. There is considerable overlap between PNH, aplastic anemia, and myelodysplastic syndrome and some cases evolve into acute leukemia. Treatment is mainly supportive consisting of transfusion therapy, anticoagulation, and antibiotic therapy. Hematopoietic stem cell transplantation may be curative.

Anemia↗

PubMed1996

[Paroxysmal nocturnal hemoglobinuria].

Paroxysmal Nocturnal Hemoglobinuria (PNH) is an acquired hemolytic anemia characterized by chronic hemolysis, deep thrombosis, and hypoplastic marrow, and thought to be a clonal hematopoietic stem cell disorder. Affected blood cells are deficient in glycosylphosphatidylinositol (GPI)-anchored cell surface proteins. Recent investigations revealed that the PIG-A gene, which participates the biosynthesis of the GPI-anchor, was identified and the mutations were detected in the patients with PNH. Here we discuss the following problems related to the PIG-A gene; (1) the inconsistency of the expression of the GPI-anchored proteins and the mutations of the PIG-A gene, (2) the existence of the multiple PNH clones bearing different PIG-A mutations in a single patient, (3) aplastic anemia-PNH syndrome and PIG-A gene.

Animals↗

PubMedDate not supplied

The PIG-A gene somatic mutation responsible for paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria is the first example of a non neoplastic human disease caused by the somatic mutation of an X-linked gene. The PIG-A gene maps to Xp22.1 and is required for the transfer of N-acetyl glucosamine to phosphoinositol, an early step in the production of the GPI anchor. A deficiency of GPI-linked proteins on the cell surface is responsible for the PNH cell defect, which can be detected by flow cytometry not only on red cells, but also on myeloid cells and in some patients even on lymphoid cells. Its location on the X-chromosome explains how a single recessive mutation can cause the appearance of the abnormal clone. A number of patients may have more than one PNH clone, suggesting that the expansion of GPI-deficient clones occurs under the pressure of a selection mechanism.

Genetic Linkage↗

PubMed1989

Erythrocyte membrane protein deficiencies in paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired disorder characterized by intermittent hemolytic anemia. Membrane abnormalities of blood cells from patients with PNH are the reason for the unusual sensitivity to lysis by autologous plasma complement. A patient with typical clinical disease consistent with PNH is described together with a few strategies and pitfalls for treatment. Commonly used in vitro assays are discussed that document the complement-mediated lysis of aberrant PNH erythrocytes. Membrane-associated proteins that are abnormal in PNH cells, the characteristics of these proteins, and their mechanism(s) of action are described; these include the decay accelerating factor that inhibits the C3/C5 convertases of both complement pathways on cell surfaces, the C8 binding protein that modulates a step in terminal complement lysis, and other proteins that regulate complement-mediated lysis at early or late steps of the complement cascade.

Adult↗

PubMed1994

Mutations within the Piga gene in patients with paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal hematologic disorder with multiple and varied clinical manifestations. The biochemical defect in PNH resides in the incomplete enzymatic assembly of glycosylphosphatidylinositol (GPI) anchors used for surface protein attachment. In all patients tested thus far, the defect is at the level of N-acetylglucosamine attachment to phosphatidylinositol (complementation class A defect). A human cDNA, Piga, that repairs cell lines with the class A defect has been recently cloned, making Piga a candidate gene for PNH. In the current study, using highly purified GPI-deficient granulocytes, we have performed Northern blot and reverse transcriptase polymerase chain reaction (RT-PCR) analysis of Piga in four patients with PNH. In each case, we have identified a mutation in the Piga coding sequence: three frameshift mutations were found, and a single nucleotide substitution (missense) mutation was identified. Our results provide convincing evidence that alterations in the Piga gene are responsible for PNH.

Adult↗

PubMed1993

Deficient biosynthesis of N-acetylglucosaminyl-phosphatidylinositol, the first intermediate of glycosyl phosphatidylinositol anchor biosynthesis, in cell lines established from patients with paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is a hemolytic disorder caused by a deficiency of biosynthesis of the glycosyl phosphatidylinositol (GPI) anchor, but the biochemical defect is not completely understood. In the present study, we have analyzed affected cell lines established recently from two Japanese patients with PNH. Two lines of evidence indicate that these cells do not synthesize N-acetylglucosaminyl-phosphatidylinositol, the first intermediate in the GPI anchor biosynthesis. First, somatic cell hybridization analysis using Thy-1-deficient murine thymoma cell lines with known biochemical defects as fusion partners showed that the PNH cell lines belong to complementation class A, which is known not to synthesize N-acetylglucosaminyl-phosphatidylinositol. Second, analysis of in vitro glycolipid biosynthesis demonstrated that cell lysates of these PNH cell lines in fact did not support biosynthesis of N-acetylglucosaminyl-phosphatidylinositol. Thus, we have characterized for the first time the exact biochemical defect leading to PNH.

Cells, Cultured↗

PubMed2006

Reticulocyte-gated flow cytometric analysis of red blood cells in paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is a hematopoietic stem cell disorder characterized by the deficiency of glycosyl phosphatidylinositol (GPI)-anchored proteins in the affected blood cell membranes. Analysis of blood cells by flow cytometry is useful to identify the affected blood cells with PNH-specific phenotypes. Because PNH-affected red blood cells (RBC) have shortened life-spans in the circulation, ratios of PNH-affected populations analyzed by flow cytometry in whole RBC are lower than those in PNH-affected erythropoiesis. We developed a reticulocyte-gated 2-color flow cytometry of RBC and revealed that the percentages of PNH-affected, CD59--populations in reticulocytes were higher than in whole RBC in patients with PNH. A serial analysis of a patient with PNH who underwent peripheral blood stem cell transplantation confirmed the usefulness of this method to evaluate PNH-affected RBC populations with high sensitivity; ie, the presence of CD59- reticulocytes in the circulation could be a sensitive marker for PNH-affected erythropoiesis.

CD59 Antigens↗

PubMed1993

[Recent advances in research on paroxysmal nocturnal hemoglobinuria].

Paroxysmal nocturnal hemoglobinuria (PNH) is a hemolytic anemia caused by complement-mediated hemolysis. Blood cells from patients with PNH contain abnormal cells that lack complement regulatory proteins, DAF and CD59, both of which protect host cells from action of complement. DAF and CD59 are GPI-anchored and on the abnormal blood cells other GPI-anchored proteins are also deficient. A fundamental abnormality of PNH appeared to be deficient biosynthesis of the GPI-anchor at an early step. We cloned a cDNA of a gene termed PIG-A (for Phosphatidyl Inositol Glycan-class A) that encodes a 484 amino acid putative ER membrane protein which functions at that step and hence a responsible gene for PNH. Analysis of PIG-A transcripts in the abnormal cells from patients with PNH demonstrated various types of abnormalities such as decreased level of the transcript, splicing abnormality and mutations in the coding region. Thus, PNH is caused by a clonal expansion of abnormal blood cells derived from a hematopoietic stem cell bearing a somatic mutation occurred in PIG-A gene.

Amino Acid Sequence↗

PubMed1991

[Altered metabolism of membrane glycosphingolipids in erythrocytes of paroxysmal nocturnal hemoglobinuria].

Paroxysmal nocturnal hemoglobinuria (PNH) is currently accepted to be a stem-cell disorder of a clonal nature with increased susceptibility to autologous complement attack. Consequent hemolytic feature has been partly explained by lack of complement regulatory membrane proteins such as decay-accelerating factor (DAF) or C8-binding protein that anchored to membrane via glycosyl-phosphatidyl inositol (GPI) lipids. Recent reports suggest essential PNH lesion is the synthetic defect of sugar moiety of the PI-anchor. In PNH, the abnormal expression of C3b/C4b receptor (CRI) glycoproteins, or glycophorin-alpha have been also pointed out. These altered expression of glycoproteins and glyceroglycolipids, especially in the carbohydrate structures, prompted us to analyze biochemically the membrane glycosphingolipids as one of major glycoconjugates in PNH. As results, PNH erythrocytes showed altered metabolism of gangliosides in comparison to control erythrocytes from healthy donors. IV6 NeuAc-nLc4 Cer and highly polar gangliosides variably disappeared in PNH erythrocytes, partly due to impaired sialylation of glycolipids. These results suggest metabolic disorder of carbohydrates of membrane glycoconjugates as a new aspect of PNH.

Adult↗

PubMed2003

Recent insights into the pathophysiology of paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is a unique clonal stem cell disorder characterized by intravascular hemolysis, thrombotic events and bone marrow failure. There has been accelerated progress in understanding the mechanisms underlying the clinical features of the disease over the last decade. The development of PNH requires not only a somatic mutation of the phospatidylinositol glycan complementation class A (PIG-A) gene, but also a survival advantage of the PNH clone ('dual pathogenesis' theory). There is increasing evidence that negative selection against the non-mutated cells rather than positive selection of the PIG-A gene mutant cells is responsible for the dominance of the PNH clone. In this review, we summarize the important advances in the understanding of PNH, but we also concentrate on the presence of PNH clones in other hematological disorders, including aplastic anemia (AA), myelodysplastic syndromes (MDS), acute leukemias, and myeloproliferative and lymphoproliferative syndromes. The fuller comprehension of the pathophysiology of PNH may have wider implications than for PNH itself, as indicated by the presence of PNH clones in these hematological malignancies, and by the therapeutic implications of this fact, as already described in patients with AA and MDS.

Anemia, Aplastic↗

PubMed1994

Characterization of genomic PIG-A gene: a gene for glycosylphosphatidylinositol-anchor biosynthesis and paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired hemolytic anemia characterized by the presence of abnormal subpopulations of blood cells that are deficient in surface expression of glycosylphosphatidylinositol (GPI)-anchored proteins. Recent studies showed that the gene termed PIG-A, which participates in the first step of GPI-anchor biosynthesis, is mutated in the abnormal blood cells from patients with PNH. In this study the genomic PIG-A gene was cloned and characterized to obtain nucleotide sequence information for analyzing somatic mutations of PIG-A in patients with PNH. The PIG-A gene is at least 17 kb long and has six exons. The exon-intron boundaries and 583 bp of the 5' flanking region were sequenced. The 5' flanking region has no TATA-like sequence, but includes four CAAT boxes, two AP-2 sequences, and a CRE sequence, some of which are present in regions necessary for the promoter activity. We report pairs of oligonucleotide primers for polymerase chain reaction that should be useful to amplify and analyze various regions of the PIG-A gene in patients with PNH.

Base Sequence↗

PubMed2006

New insights into paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is an uncommon intravascular hemolytic anemia that results from the clonal expansion of hematopoietic stem cells harboring somatic mutations in an X-linked gene, termed PIG-A. PIG-A mutations block glycosylphosphatidylinositol (GPI) anchor biosynthesis, resulting in a deficiency or absence of all GPI-anchored proteins on the cell surface. CD55 and CD59 are GPI-anchored complement regulatory proteins. Their absence on PNH red cells is responsible for the complement-mediated intravascular hemolysis. Intravascular hemolysis leads to release of free hemoglobin, which contributes to many of the clinical manifestations of PNH including fatigue, pain, esophageal spasm, erectile dysfunction and possibly thrombosis. Interestingly, rare PIG-A mutations can be found in virtually all healthy control subjects, leading to speculation that PIG-A mutations in hematopoietic stem cells are common benign events. However, negative selection of PIG-A mutant colony-forming cells with proaerolysin, a toxin that targets GPI-anchored proteins, reveals that most of these mutations are not derived from stem cells. Recently, a humanized monoclonal antibody directed against the terminal complement protein C5 has been shown to reduce hemolysis and greatly improve symptoms and quality of life for PNH patients.

Antibodies, Monoclonal↗

PubMed2001

Proliferative capacity of single isolated CD34+ hematopoietic stem/progenitor cells in paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) results from somatic mutations of the X-linked PIG-A (phosphatidylinositol glycan-class A) gene, which occurs on a hematopoietic stem cell level, leading to a proportion of blood cells being deficient in all glycosylphosphatidylinositol (GPI)-anchored surface proteins. Although these GPI-deficient cells can explain many of the clinical symptoms of PNH, the pathogenesis of PNH is still somewhat obscure and many questions remain. To assess the hematopoietic defect involved in PNH, CD34+ CD59+ (normal phenotype hematopoietic stem/progenitor) and CD34+ CD59- (PNH phenotype) cells from PNH patients (n = 16) and CD34+ CD59+ cells from healthy volunteers (n = 10) were sorted as single cells into 96-well flat-bottom culture plates containing culture medium supplemented with stem cell factor, interleukin (IL)-3, erythropoietin, granulocyte-macrophage-colony-stimulating factor (GM-CSF), G-CSF, IL-6, thrombopoietin, and Flt-3 ligand. We found that the single PNH CD34+ CD59- cells had a growth advantage over the single CD34+ CD59+ cells to some extent, but they both had impaired growth abilities compared with CD34+ cells from healthy volunteers.

Adolescent↗

PubMed2003

Laboratory diagnosis of paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is an uncommon acquired stem cell disorder associated with periodic hemolytic events. This benign clonal disease is caused by abnormalities of the X-linked phosphatidylinositol glycan class A (PIGA) gene and is associated with cytopenias and thrombosis. Although the trilineage of bone marrow elements is affected, involvement of the red blood cell (RBC) line was recognized first due to its abnormal sensitivity to complement-mediated intravascular hemolysis. Totally or partially deficient blood cell membrane proteins include decay accelerating factor (DAF, CD55), membrane inhibitor of reactive lysis (MIRL, CD59), and other proteins attached to the glycophosphatidylinositol (GPI) spine. Stem cell transplantation can be curative in PNH. Diverse laboratory abnormalities observed in PNH include bone marrow hyper- and hypoplasia, hematologic cytopenias, micro- and macrocytosis, decreased leukocyte alkaline phosphatase (LAP), hemoglobin- and hemosiderinuria, as well as associated iron deficiency. The more definitive laboratory tests comprise older biochemical and newer flow cytometric (FCM) procedures. The former group includes the sucrose hemolysis test for screening and Ham's acid hemolysis test for confirmation; the latter group includes FCM analyses of CD55 and CD59, which have recently replaced Ham's test, and FCM quantification of specific GPI-anchor binding using fluorescent-labeled inactive toxin aerolysin (FLAER). FLAER is more sensitive than FCM quantification of antibody-binding to CD59 for PNH diagnosis.

Clinical Laboratory Techniques↗

PubMed1994

Chromosomal assignment of genes involved in glycosylphosphatidylinositol anchor biosynthesis: implications for the pathogenesis of paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal hematologic disorder that affects both sexes equally. The biochemical defect in PNH resides in the incomplete enzymatic assembly of glycosylphosphatidylinositol (GPI) anchors used for surface protein attachment. In all PNH patients tested to date, the biosynthetic defect occurs at the addition of N-acetyl-glucosamine to the phosphatidylinositol molecule (class A defect). A human cDNA, Piga, that repairs cell lines with the class A GPI-anchor biosynthetic defect has been recently cloned. Mapping of Piga to the X chromosome suggests that a single acquired mutation within Piga could alter GPI-anchor synthesis and result in PNH. However, this finding does not explain why all PNH patients have the class A defect. In the current study, the chromosomal assignment of Piga, as well as of Pigf and Pigh, two additional genes involved in GPI-anchor biosynthesis, has been established using a mouse interspecific backcross mapping technique. In contrast to Piga, both human and mouse Pigf and Pigh genes map to autosomes. The location of Pigf and Pigh suggests that mutations on both alleles of these autosomal genes would be necessary to produce PNH. This helps to explain the predominant class A defect in PNH.

Animals↗

PubMed1995

Markedly high population of affected reticulocytes negative for decay-accelerating factor and CD59 in paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) blood cells lack glycosylphosphatidylinositol-anchored membrane proteins such as decay-accelerating factor (DAF) and CD59. This lack is of diagnostic value in PNH. Because reticulocytes in PNH are not yet well characterized, we analyzed reticulocytes obtained from 12 patients with PNH and from 5 healthy volunteers by two-color flow cytometry with a membrane-permeable fluorescent dye, thiazole orange, to identify reticulocytes and monoclonal antibodies to DAF and CD59. Healthy individuals had no affected cells. In all patients, the population of affected reticulocytes negative for DAF and CD59 was markedly higher than the population of affected erythrocytes. Moreover, the population of affected erythrocytes became obviously low in patients who received transfusions and suffered from hemolytic precipitation, whereas the population of affected reticulocytes was unchanged. The persistently high population of affected reticulocytes, despite cytolytic exclusion and an inherently short lifetime, might possibly be explained by relative reticulocytosis caused by an anemia-induced feedback stimulation of erythropoiesis in PNH. Thus, affected reticulocytes could be a reliable marker for the diagnosis of PNH and for the evaluation of erythropoiesis by PNH stem cell.

Adolescent↗