Pulmonary hypertension in paroxysmal nocturnal hemoglobinuria.

Pulmonary arterial hypertension (PAH) and cor pulmonale were found in a patient with paroxysmal nocturnal hemoglobinuria (PNH). Autopsy revealed widespread thromboses in pulmonary microvasculature. Vascular thromboses attributed to hypercoagulability have been found in PNH in many organs, including the lungs. PAH has not been reported, however. This disease should then be considered a rare cause of PAH.     

Thrombosis in patients with paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria is a disorder associated with hemolysis, pancytopenia, and thrombosis due to the loss of the glycosylphosphatidylinositol (GPI) anchored complement regulatory proteins. The mechanism of thrombosis is multifactorial. Although intravascular hemolysis has been implicated as the etiology, the effect of complement on GPI anchor-deficient platelets, granulocytes, monocytes, and endothelial cells contributes significantly to the risk of thrombosis. Moreover, there appears to be an underlying inflammatory state that is linked to hemostatic activation that may induce thrombosis through a pathway independent of hemolysis.     

Marrow transplantation for paroxysmal nocturnal hemoglobinuria.

Between 1971 and 1990, nine patients ranging in age from 14-38 years received marrow transplants for paroxysmal nocturnal hemoglobinuria (PNH). Six were transplanted for aplastic complications of PNH. Four of these were from HLA-identical siblings, and the patients were conditioned with cyclophosphamide. One graft was form a syngeneic twin without conditioning, and one from a two HLA-antigen nonidentical father after conditioning with cyclophosphamide and total body irradiation. Three of the four recipients of allogeneic marrow developed acute and two chronic graft-versus-host disease (GVHD). Five of six transplanted for severe aplastic anemia are long-term survivors with follow-up ranging from more than 6.2 to more than 19.1 years. The HLA nonidentical transplant recipient experienced graft rejection and died of a pulmonary hemorrhage. Three patients were transplanted for nonaplastic complications of PNH consisting of life threatening recurrent thromboses or refractory hemolysis. Two of these patients received marrow grafts from HLA-identical siblings after conditioning with busulfan and cyclophosphamide. They are surviving with normal hemograms greater than 2.2 and greater than 2.5 years and had mild chronic GVHD which resolved, although one has biochemical evidence of PNH in 15% of the red cells. One received a syngeneic marrow graft without conditioning but reverted to PNH. He is alive greater than 8.6 years after transplantation. Marrow transplantation for aplastic complications of PNH is successful, well tolerated, and compatible with long-term survival when an HLA-identical sibling or a syngeneic donor is available. For patients without aplasia, one must weigh the complications of transplantation with the life threatening nature of thrombotic episodes and hemolysis.     

Complement-mediated granulocyte dysfunction in paroxysmal nocturnal hemoglobinuria.

In paroxysmal nocturnal hemoglobinuria (PNH), infection, both viral and bacterial, disproportionate to the mild neutropenia seen in many such patients is responsible for significant morbidity. We report impaired granulocyte chemotaxis efficiency which may contribute to the problems induced by bacterial infections. PNH (but not normal) granulocytes, after exposure to very small concentrations of activated serum complement components, migrate poorly, as documented by their inhibited chemotaxis toward bacterial products or activated complement components in Boyden chambers. The granulocytes remain intact, excluding trypan blue, phagocytosing, and killing bacteria, despite this activated complement exposure. It is also suggested that this chemotactic defect may involve only a clone of cells, analogous to the clonal lysis of PNH erythrocytes; those few granulocytes capable of migration after exposure to activated complement contain normal quantities of leukocyte alkaline phosphatase (LAP), in contrast to the LAP deficiency of the overall PNH granulocyte population. Since bacterial infection may initiate or potentiate hemolysis, one of the major symptoms of the disease, these results could explain much of the morbidity of PNH.     

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 ≥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. Am. J. Hematol. 54:149–154, 1997 © 1997 Wiley-Liss, Inc.     

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.     

The kidneys in paroxysmal nocturnal hemoglobinuria

Long-term study of 21 PNH patients revealed an unexpectedly high incidence of functional and anatomic renal abnormalities. Most patients demonstrated varying degrees of hematuria and proteinuria distinct from hemoglobinuria. Evaluation of renal function revealed hyposthenuria, abnormal tubular function, and declining creatinine clearance. Radiologically these patients had enlarged kidneys, cortical infarcts, cortical thinning, and papillary necrosis which were confirmed by autopsy studies. Hypertension developed in eight patients. Urinary tract infection was uncommon. The renal findings bear striking similarity to those of sickle cell anemia. Contrary to the usual opinion, out studies clearly showed evidence of widespread renal pathology in PNH most likely due to repeated microvascular thrombosis similar to the venous thrombosis involving other organs in this disorder.     

HLA antigens in paroxysmal nocturnal hemoglobinuria

10 patients with paroxysmal nocturnal hemoglobinuria were studied taking 109 normal subjects of the Cuban population as control group. 26 HLA antigens corresponding to loci A and B were studied in both groups. Phenotypical frequency of both groups were compared. No statistically significant increase was found for any of the studied antigens, though there was a nonsignificant increase for antigens HLA-B7 and BW-21. These results might be influenced by the small number of patients studied due to the rareness of the disease.     

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.     

Evans' syndrome in paroxysmal nocturnal hemoglobinuria

We describe the first case of paroxysmal nocturnal hemoglobinuria with Evans' syndrome. The immunohematological studies of this patient, a 27-year-old man, revealed the presence of red cell and platelet autoantibodies, related to an episode of anemia and thrombocytopenia.     

Corticosteroids therapy in paroxysmal nocturnal hemoglobinuria

We evaluated the efficacy of alternate day, high dose prednisolone for the treatment of paroxysmal nocturnal hemoglobinuria (PNH). Nineteen patients were included. Thirteen were men and six were women, aged between 13-56 years. Eleven patients improved, eight with good response and three with fair response. Eight patients were non-responders. Responders had gradual improvement in the hemoglobin level, but none achieved a normal hemoglobin level. Age at diagnosis, sex, initial hemoglobin, white count, and percentage of a positive Ham's test had no apparent bearing on treatment outcome. A prolonged interval from diagnosis to prednisolone treatment decreased the chance of a favorable hematologic response to therapy. Age at the treatment in non-responders was higher than responders. Responders had higher numbers of colonies derived from BFU-E and CFU-GM both in the blood and bone marrow than non-responders although the differences did not achieve statistical significance. These data indicate that alternate day, high dose prednisolone therapy is effective in some patients with PNH.     

Neutral evolution in paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria is an acquired hematopoietic stem cell (HSC) disorder characterized by the partial or complete deficiency of glycosyl-phosphatidylinositol (GPI)-linked membrane proteins, which leads to intravascular hemolysis. A loss of function mutation in the PIG-A gene, required for GPI biosynthesis, explains how the deficiency of many membrane proteins can result from a single genetic event. However, to date the mechanism of expansion of the GPI⁻ clone has not been fully understood. Two hypotheses have been proposed: A selective advantage of GPI⁻ cells because of a second mutation or a conditional growth advantage of GPI⁻ cells in the presence of an immune attack on normal (GPI⁺) HSCs. Here, we explore a third possibility, whereby the PNH clone does not have a selective advantage. Simulations in a large virtual population accurately reproduce the known incidence of the disease; and the fit is optimized when the number of stem cells is decreased, reflecting a component of bone marrow failure in PNH. The model also accounts for the occurrence of spontaneous cure in PNH, consequent on clonal extinction. Thus, a clonal advantage may not be always necessary to explain clonal expansion in PNH.     

Two populations of granulocytes in paroxysmal nocturnal hemoglobinuria.

The granulocytes in paroxysmal nocturnal hemoglobinuria (PNH) are defective, and the defect is similar to that previously described for the PNH erythrocyte. Using anti-I antibody to activate complement and 51Cr release to detect cell lysis, we found two populations of granulocytes that differed in their susceptibility to lysis by complement in 5 of 6 patients. A proportion of the cells were lysed by one-fifteenth to one-twentieth the amount of complement required to lyse normal cells; the remainder of the granulocytes appeared to be normal in their susceptibility to the lytic action of complement. The binding of the third component of complement (C3) to PNH granulocytes was at least twice that bound to normal cells, even though the binding of antibody was the same for normal and PNH cells. This suggests that the binding of C3 and probably the efficiency of the terminal steps of complement lysis are increased in the abnormal PHN granulocyte. These defects affect only a portion of the granulocytes, thus suggesting that the disorder is a clonal stem cell abnormality.     

Laboratory tests for paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare hematological disorder that is often suspected in a patient presenting with non‐immune hemolytic anemia associated with pancytopenia or venous thrombosis. This disorder is a consequence of acquired somatic mutations in the phosphatidylinositol glycan class A (PIG‐A) gene in the hematopoietic stem cells (HSC) of patients. The presence of these mutations leads to production of blood cells with decreased glycosyl phosphatidylinositol‐anchored cell surface proteins, making red blood cells derived from the clone more sensitive to complement mediated hemolysis. The diagnosis of PNH may be difficult in some cases due a low proportion of PNH cells in the blood and occasionally due to difficulties in selecting the most appropriate diagnostic studies. The latest generation of tests allow for detection of very small populations of PNH cells, for following the natural course and response to therapy of the disease, and for helping to decide when to initiate therapy with monoclonal antibody targeting the terminal complement protein C5 (Eculizumab), anticoagulation, and in some cases allogeneic HSC transplant. In this article, we review the different diagnostic tests available to clinicians for PNH diagnosis. Am. J. Hematol. 89:339–341, 2014. © 2013 Wiley Periodicals, Inc.     

The pathophysiology of paroxysmal nocturnal hemoglobinuria

The molecular basis of PNH is known. Somatic mutation of the X-chromosome gene PIGA accounts for deficiency of glycosyl phosphatidylinositol-anchored proteins (GPI-AP) on affected hematopoietic stem cells and their progeny. However, neither mutant PIGA nor the consequent deficiency of GPI-AP provides a direct explanation for the clonal outgrowth of the mutant stem cells. Therefore, PNH differs from malignant myelopathies in which clonal expansion is directly attributable to a specific, monogenetic event (e.g., t(9;22) in CML) that bestows a growth/survival advantage upon the affected cell. Multiple, discrete PIGA mutant clones are present in many patients, suggesting that a selection pressure that favors the PNH phenotype (i.e., GPI-AP deficiency) was applied to the bone marrow. The nature of this putative selection pressure, however, is speculative, as is the basis of clonal expansion. In many patients, the majority of hematopoiesis is derived from PIGA mutant stem cells. Yet clonal expansion is limited (nonmalignant), and the contribution of the mutant clones to hematopoiesis may remain stable for decades. Understanding the basis of clonal selection and expansion will not only delineate further the pathophysiology of PNH but also provide new insights into stem cell biology and suggest novel therapeutic strategies for enhancing marrow function.     

New insights into paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is an uncommon acquired hemolytic anemia that manifests with abdominal pain, esophageal spasm, fatigue, and thrombosis. The hallmark of PNH at the cellular level is a deficiency in cell surface glycosylphosphatidylinositol anchored proteins; this deficiency on erythrocytes leads to intravascular hemolysis. Free hemoglobin from hemolysis leads to circulating nitric oxide depletion and is responsible for many of the clinical manifestations of PNH, including fatigue, erectile dysfunction, esophageal spasm, and thrombosis. The recently FDA approved complement inhibitor eculizumab has been shown to decrease hemolysis, decrease erythrocyte transfusion requirements, and improve quality of life for PNH patients.