Mechanism of intravascular hemolysis in paroxysmal nocturnal hemoglobinuria (PNH)

Paroxysmal nocturnal hemoglobinuria (PNH) hemolysis requires both intravascular complement activation and affected erythrocytes susceptible to complement. This susceptibility is explained by a deficiency in complement regulatory membrane proteins that are attached to the membrane by a glycosylphosphatidylinositol (GPI) anchor. Affected cells lack a series of GPI-anchored membrane proteins with various functions. The lack is caused by a synthetic defect of the anchor due to an impaired transfer of N-acetylglucosamine to phosphatidylinositol which is an early metabolic precursor in the anchor synthesis. Moreover, PIG-A gene responsible for the membrane defect was recently cloned. Further, a possible mechanism of complement activation has been proposed, especially for an infection-induced hemolytic precipitation which is clinically crucial. Thus, the molecular events, leading to intravascular hemolysis characteristic of PNH, has been virtually clarified. Next major concern is the nature of PIG-A: How does PIG-A explain the complex pathophysiology of PNH which exhibits various clinical manifestations? © 1996 Wiley-Liss, Inc.     

Primary prophylaxis with warfarin prevents thrombosis in paroxysmal nocturnal hemoglobinuria (PNH)

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired hemolytic anemia in which venous thrombosis is the most common cause of death. Here we address the risk factors for thrombosis and the role of warfarin prophylaxis in PNH. The median follow-up of 163 PNH patients was 6 years (range, 0.2-38 years). Of the patients, 29 suffered thromboses, with a 10-year incidence of 23%. There were 9 patients who presented with thrombosis, and in the remainder the median time to thrombosis was 4.75 years (range, 3 months-15 years). The 10-year risk of thrombosis in patients with large PNH clones (PNH granulocytes > 50%) was 44% compared with 5.8% with small clones (P <.01). Patients with large PNH clones and no contraindication to anticoagulation were offered warfarin. There were no thromboses in the 39 patients who received primary prophylaxis. In comparison, 56 patients with large clones and not taking warfarin had a 10-year thrombosis rate of 36.5% (P =.01). There were 2 serious hemorrhages in more than 100 patient-years of warfarin therapy. Large PNH granulocyte clones are predictive of venous thrombosis, although the exact cut-off for clone size is still to be determined. Primary prophylaxis with warfarin in PNH prevents thrombosis with acceptable risks.     

Treatment of paroxysmal nocturnal hemoglobinuria

Patients with PNH may be treated with a number of known agents. As in all patients with a chronic disease, a regimen tolerable over a long period of time must be selected. Knowledge and anticipation of complications and their proper treatment are essential parts in the treatment. When these principals are used, many patients may live reasonable lives for very long periods of time.     

阵发性睡眠性血红蛋白尿并发缺血性肠病临床特点分析

阵发性睡眠性血红蛋白尿症（paroxysmal nocturnal hemoglobinuria,PNH）是一种罕见的获得性造血干细胞疾病。PNH胃肠道受累非常少见。本研究旨在总结和分析PNH并发缺血性肠病的临床特点。收集并总结自2010年1月至2020年12月在北京协和医院诊断的6例PNH 并发缺血性肠病患者的临床资...     

Immunocytochemical staining of decay-accelerating factor (DAF) on erythrocytes: paroxysmal nocturnal hemoglobinuria (PNH)]

Affected erythrocytes in patients with paroxysmal nocturnal hemoglobinuria (PNH) have been detected as complement-sensitive cells by the complement sensitivity assay. Decay-accelerating factor (DAF), a molecular mass of 70 kDa complement-regulatory membrane glycoprotein, has been reported to be deficient on affected PNH blood cells. In the present study, DAF on erythrocytes from 12 patients with PNH were stained by an immunocytochemical method and the ratio of DAF+ erythrocytes was compared with their laboratory data concerning hemolysis, almost all normal human erythrocytes stained positively for DAF. In contrast, various percentages of DAF+ erythrocytes were found in the patients with PNH. The percentages of DAF+ erythrocytes correlated positively with the total amounts of DAF on erythrocytes measured by an enzyme-linked immunosorbent assay (ELISA), negatively with % hemolysis in Ham's test and in sucrose hemolysis assay and with percentages of PNH type III (PNH-III) erythrocytes. In some patients with PNH, subpopulations of erythrocytes weakly-positive for DAF were demonstrated in addition to DAF- erythrocytes. The immunocytochemical method for staining DAF on erythrocytes developed in the present study is useful for the detection of affected PNH erythrocytes and applicable to further studies on membrane defects in PNH.     

Susceptibility to autoxidation of lipids of paroxysmal nocturnal hemoglobinuria (PNH)-like red cells.

The susceptibility to autoxidation of red cell lipids was studied before and after transformation of normal red cells to PNH-like erythrocytes. The transformation was effected by treatment of the red cells with the sulfydryl compounds D-penicillamine (DP) and N-acetyl-L-cysteine (NAC). The autoxidation was induced by incubating the cells with H2O2 and was estimated by measuring the generated malonyl dialdehyde. The susceptibility to autoxidation was significantly higher in DP-treated cells, while the opposite was true for NAC-treated cells. However, both DP- and NAC-treated cells showed a similar sensitivity to lysis by acid serum and about the same degree of acetylcholinesterase (AChE) activity decrease, thus indicating that the susceptibility to autoxidation of lipids is not involved in the determination of complement sensitivity or in the AChE activity decrease of the sulfydryl-treated cells. Finally, since, as evidenced from most of the reported cases in the literature, increased susceptibility to autoxidation is a feature of PNH cells, it seems reasonable to suggest that DP-treated cells should be used in preference to NAC-treated cells as a laboratory substitute for PNH cells.     

The mutation rate in PIG-A is normal in patients with paroxysmal nocturnal hemoglobinuria (PNH)

Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by the presence in the patient's hematopoietic system of a large cell population with a mutation in the X-linked PIG-A gene. Although this abnormal cell population is often found to be monoclonal, it is not unusual that 2 or even several PIG-A mutant clones coexist in the same patient. Therefore, it has been suggested that the PIG-A gene may be hypermutable in PNH. By a method we have recently developed for measuring the intrinsic rate of somatic mutations (mu) in humans, in which PIG-A itself is used as a sentinel gene, we have found that in 5 patients with PNH, mu ranged from 1.24 x 10(-7) to 11.2 x 10(-7), against a normal range of 2.4 x 10(-7) to 29.6 x 10(-7) mutations per cell division. We conclude that genetic instability of the PIG-A gene is not a factor in the pathogenesis of PNH.     

Treatment of paroxysmal nocturnal hemoglobinuria with danazol

Glucocorticoid and androgen therapy have been used with moderate success in paroxysmal nocturnal hemoglobinuria (PNH). However, both are poorly tolerated, especially in women, although the side effects of glucocorticoid can be diminished by alternate day therapy. We have treated two patients with PNH with danazol. One of patient is man, 64 years old age with stomach cancer, and the other patient is 34-year-old man. Their disease has existed for 6-14 years. They required many blood transfusions, their hemoglobins ranging between 7.1 and 9.9 grams per deciliter. When treated with danazol by mouth, the hemoglobin level increased approximately 2 to 5 grams in each patient within 3 week, and clinical hemoglobinuria improved. None of the patients has had any side effects.     

Effect of heparin on complement activation and lysis of paroxysmal nocturnal hemoglobinuria (PNH) red cells.

The effect of heparin upon the binding of the third component of complement (C3) to PNH red cells in vitro and their subsequent hemolysis is described. Heparin, in increasing concentrations, progressively inhibits membrane C3 fixation and hemolysis when the classic complement pathway is activated by anti-red cell antibodies. Heparin has a biphasic effect upon membrane C3 fixation and hemolysis when complement is activated in serum at decreased ionic strength (sucrose lysis) or in serum at decreased pH (Ham test). Heparin in concentrations above 2 U/ml inhibits C3 binding and hemolysis while lower concentrations of heparin enhance the consequences of complement activation by these two procedures. This enhanced complement activation may explain the increased hemolysis sometimes reported in PNH patients treated with heparin, and suggests that heparin may aggravate the consequences of pathologic alternative pathway complement activation in other diseases.     

Chronic myelomonocytic leukemia (CMMoL) with systemic lymph node swelling and paroxysmal nocturnal hemoglobinuria (PNH)-like complication

A 37-year-old male was diagnosed as having chronic myelomonocytic leukemia (CMMoL) with chief complaint of systemic lymph node swelling. On admission, his peripheral blood revealed mild anemia and mild thrombocytopenia with giant platelets, and monocytosis (1480/microliters). NAP score was low. Serum lysozyme increased. The bone marrow showed normal cellularity consisting of 4% myeloblasts and 14.4% promyelocytes, and a few myeloid cells were positive for double staining by alpha-naphthyl butyrate and naphthol ASD chloroacetate esterase. Biopsied specimens of the cervical lymph node showed infiltration of monocytoid cells, which were positive for lysozyme staining, into interfollicular tissue. As for chromosome variation, 21 large satellite was observed in all dividing cells from his bone marrow and peripheral blood. Furthermore, hemolytic anemia with hemoglobinuria developed during his course. Sugar water test was positive, but Ham test negative. Coombs test and Donath-Landsteiner reaction were negative. Abnormal hemoglobin, spherocyte and fragmentation were not found. Hemolysis disappeared about two months later. However, blastic crisis appeared and he died. We showed a case of CMMoL with 21 large satellite and paroxysmal nocturnal hemoglobinuria (PNH)-like complication. Satellite have usually been reported as asymptomatic, and thus this chromosome variant and CMMoL may have been coincidentally observed.     

Clinical features of paroxysmal nocturnal hemoglobinuria (PNH) in China as compared with those in United Kingdom

The clinical features of 26 patients of PNH in Sheffield Blood Centre, UK and 50 cases in our hospital, observed in the same period, were compared. Each case was analysed according to the same criteria, and then comparison was made between the two groups. Results showed that in our group: male patients were more common; patients usually had mild or moderate bleeding tendency; the appearance of hemoglobinuria was delayed; abdominal pain was mostly related to hemoglobinuria but not thrombosis; pancytopenia was encountered more frequently and leucopenia as well as thrombocytopenia more remarkable; the incidence of thrombosis was not rare, but occurred rather late: thrombosis was mainly seen in superficial veins, but not veins of viscera; the major cause of death was not thromboembolism but infection. About 25% of the patients achieved long term clinical remission in both groups. None of the patients in these two series transformed to myeloproliferative disorders including acute leukemia. PNH can be considered a benign and chronic hematologic disease.