Effect of the complement inhibitor eculizumab on thromboembolism in patients with paroxysmal nocturnal hemoglobinuria

Hemolysis and hemoglobinemia contribute to serious clinical sequelae in hemolytic disorders. In paroxysmal nocturnal hemoglobinuria (PNH) patients, hemolysis can contribute to thromboembolism (TE), the most feared complication in PNH, and the leading cause of disease-related deaths. We evaluated whether long-term treatment with the complement inhibitor eculizumab reduces the rate of TE in patients with PNH. Clinical trial participants included all patients in the 3 eculizumab PNH clinical studies, which recruited patients between 2002 and 2005 (n = 195); patients from these studies continued treatment in the current multinational open-label extension study. Thromboembolism rate with eculizumab treatment was compared with the pretreatment rate in the same patients. The TE event rate with eculizumab treatment was 1.07 events/100 patient-years compared with 7.37 events/100 patient-years (P < .001) prior to eculizumab treatment (relative reduction, 85%; absolute reduction, 6.3 TE events/100 patient-years). With equalization of the duration of exposure before and during treatment for each patient, TE events were reduced from 39 events before eculizumab to 3 events during eculizumab (P < .001). The TE event rate in antithrombotic-treated patients (n = 103) was reduced from 10.61 to 0.62 events/100 patient-years with eculizumab treatment (P < .001). These results show that eculizumab treatment reduces the risk of clinical thromboembolism in patients with PNH. This study is registered at http://clinicaltrials.gov (study ID no. NCT00122317).

The hypercoagulable states

Patients are considered to have hypercoagulable states if they have laboratory abnormalities or clinical conditions that are associated with an increased risk of thrombosis (prethrombotic states) or if they have recurrent thrombosis without recognizable predisposing factors (thrombosis-prone). The number of specific primary hypercoagulable states that are recognized is growing. These disorders are generally inherited abnormalities of coagulation in which a physiologic anticoagulant mechanism is defective: for example, antithrombin III deficiency, protein C and protein S deficiency, abnormalities of the fibrinolytic system, and dysfibrinogenemias. Secondary hypercoagulable states are generally acquired disorders in patients with underlying systemic diseases or clinical conditions known to be associated with an increased risk of thrombosis: for example, malignancy, pregnancy, use of oral contraceptives, myeloproliferative disorders, hyperlipidemia, diabetes mellitus, and abnormalities of blood vessels and rheology. The complex pathophysiologic features of these secondary hypercoagulable states are discussed, and a framework is provided for the laboratory investigation and systematic clinical approach to the patient.

Paroxysmal nocturnal haemoglobinuria: long-term follow-up and prognostic factors. French Society of Haematology

BACKGROUND

Paroxysmal nocturnal haemoglobinuria (PNH) is a rare acquired disorder of haematopoietic stem cells. Although knowledge about the pathophysiology of the disease is increasing, no multivariate analysis of factors influencing survival has been undertaken, mainly because the disease is rare. We undertook such an investigation.

METHODS

Data were collected on 220 patients with PNH diagnosed over a 46-year period (1950-1995) from participating French centres. Diagnosis of the disease required, at least, an unequivocally positive Ham's test.

FINDINGS

The Kaplan-Meier survival estimate was 65% (SE 4) at 10 years and 48% (6) at 15 years after diagnosis. 8-year cumulative incidence rates of the main complications (pancytopenia, thrombosis, and myelodysplastic syndrome) were 15% (3), 28% (4), and 5% (2), respectively. Demographic data, presenting features, initial treatment, complications, and causes of death were similar to those previously reported. In multivariate analysis, seven factors were significantly associated with survival in patients with PNH. Poor survival was associated with the occurrence of thrombosis as a complication (relative risk 10.2 [95% CI 6-17], p < 0.0001), evolution to pancytopenia (5.5 [2.8-11], p < 0.0001), myelodysplastic syndrome or acute leukaemia (19.1 [7.3-50], p < 0.001), age over 55 years at diagnosis (4 [2.4-6.9], p < 0.0001), need for additional treatment (2.1 [1.3-3.6], p < 0.003), and thrombocytopenia at diagnosis (2.2 [1.3-3.8, p < 0.003). Better survival was shown for patients in whom aplastic anaemia antedated PNH (0.32 [0.14-0.72], p < 0.02). Factors associated in multivariate analysis with a high risk of thrombosis during the disease course were thrombosis at diagnosis (5.1 [2.5-10.6], p = 0.0002), age over 54 years (2.6 [1.5-4.6, p = 0.0014), and infection at diagnosis (2.6 [1.3-5.2], p = 0.0099). The risk factors for progression to pancytopenia were absence at diagnosis of anaemia (4.03 [1.3-12.2], p = 0.03) and neutropenia (2.45 [1.1-5.7], p = 0.03). The risk factors for development of myelodysplastic syndrome or acute leukaemia were abdominal pain crisis at presentation (10.5 [2.5-44.0], p = 0.004) and year of diagnosis after 1983 (8.45 [1.8-40.7], p = 0.004).

INTERPRETATION

This large number of cases permitted a detailed analysis of prognostic factors for the first time, in this rare disease. Estimates of PNH prognostic factors may serve as baseline data in the assessment of current and future treatments for this disease.

Paroxysmal nocturnal hemoglobinuria cells in patients with bone marrow failure syndromes

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.

Antithymocyte globulin with or without cyclosporin A: 11-year follow-up of a randomized trial comparing treatments of aplastic anemia

Immunosuppression with antithymocyte globulin, (methyl)prednisolone, and cyclosporin A is considered the treatment of choice for the patient with aplastic anemia without a donor for standard-risk stem cell transplantation. This consensus is supported by the results of several series, including a randomized German trial. Here we report 11-year results of the latter trial. With stringent response criteria and 4 months as the time to evaluate responses, this analysis confirms the superiority of the cyclosporine regimen regarding the response rate in all patients treated (70% vs 41%, with or without cyclosporine; P =.015) and in patients with severe aplastic anemia (65% vs 31%; P =.011). Patients responded more rapidly after treatment with cyclosporine (median, 60 vs 82 days; P =.019). Most patients treated with cyclosporine needed only one course of immunosuppression, whereas many patients treated without cyclosporine required repeated immunosuppressive treatment. Because of the efficacy of salvage treatment, overall survival was not different between the 2 treatment groups. However, failure-free survival favored the cyclosporine regimen (39% vs 24%; P =.04). The relapse rate, projected at 38% after 11.3 years, was similar between the 2 treatment groups. Remissions were cyclosporine dependent in 26% of the patients responding to a regimen that included cyclosporine. Clonal or malignant diseases developed in 25% of the patients. These data demonstrate that antithymocyte globulin, methylprednisolone, and cyclosporin A are an effective regimen for the treatment of aplastic anemia. However, remissions are unstable, and secondary diseases are common. In contrast to the results of stem cell transplantation, most patients are not cured.

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.

Natural history of paroxysmal nocturnal haemoglobinuria using modern diagnostic assays

Paroxysmal nocturnal haemoglobinuria (PNH) is an uncommon, acquired disorder of blood cells caused by mutation of the phosphatidylinositol glycan class A (PIG-A) gene. The disease often manifests with haemoglobinuria, peripheral blood cytopenias, and venous thrombosis. The natural history of PNH has been documented in retrospective series; but there has only been one study that correlated the more sensitive and specific flow cytometric assays that have become available in the last decade with severe symptoms associated with PNH. In a retrospective analysis of 49 consecutive patients with PNH evaluated at Johns Hopkins, large PNH clones were associated with an increased risk for thrombosis as well as haemoglobinuria, abdominal pain, oesophageal spasm, and impotence. Of the 14 (29%) patients that developed thrombosis, nine died; six of these from complications related to thromboses. According to logistic regression modelling, for a 10% change in PNH clone size, the odds ratio for risk of thrombosis was estimated to be 1.64. No patient with <61% PNH granulocytes developed a thrombosis, whereas 12 of 22 patients (54.5%) with > or =61% PNH granulocytes manifested with thrombosis. These data not only confirm that the size of the PNH clone correlates with the risk for thrombosis, but they also suggest a correlation of PNH clone size to more symptomatic PNH.

Long-term effect of the complement inhibitor eculizumab on kidney function in patients with paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is a debilitating and life-threatening disease in which lysis of PNH red blood cells frequently manifests with chronic hemolysis, anemia, and thrombosis. Renal damage in PNH is associated with chronic hemosiderosis and/or microvascular thrombosis. We determined the incidence of renal dysfunction or damage, defined by stages of chronic kidney disease (CKD), in a large cohort of PNH patients and evaluated the safety and efficacy of the complement inhibitor eculizumab in altering its progression. Renal dysfunction or damage was observed in 65% of the study population at baseline with 21% of patients with later stage CKD or kidney failure (glomerular filtration rate [GFR] <or=60 ml/min/1.73 m(2); Stage 3, 4, or 5). Eculizumab treatment was safe and well-tolerated in patients with renal dysfunction or damage and resulted in the likelihood of improvement as defined as categorical reduction in CKD stage (P < 0.001) compared with baseline and to placebo (P = 0.04). Improvement in renal function was more commonly seen in patients with baseline CKD Stages 1-2 (67.1% improvement, P < 0.001) although improvement was also observed in patients with CKD Stages 3-4 (P = 0.05). Improvements occurred quickly and were sustained for at least 18 months of treatment. Patients categorized at CKD Stages 3-5 did not worsen during treatment with eculizumab. Overall, 40 (21%) of 195 patients who demonstrated renal dysfunction or damage at baseline were no longer classified as such after 18 months of treatment. Administration of eculizumab to patients with renal dysfunction or damage was well tolerated and was usually associated with clinical improvement.

Paroxysmal nocturnal hemoglobinuria as a molecular disease

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

Increased frequency of HLA-DR2 in patients with paroxysmal nocturnal hemoglobinuria and the PNH/aplastic anemia syndrome

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.

COVID-19: A collision of complement, coagulation and inflammatory pathways

COVID-19 is frequently accompanied by a hypercoagulable inflammatory state with microangiopathic pulmonary changes that can precede the diffuse alveolar damage characteristic of typical acute respiratory distress syndrome (ARDS) seen in other severe pathogenic infections. Parallels with systemic inflammatory disorders such as atypical hemolytic uremic syndrome (aHUS) have implicated the complement pathway in the pathogenesis of COVID-19, and particularly the anaphylatoxins C3a and C5a released from cleavage of C3 and C5, respectively. C5a is a potent cell signalling protein that activates a cytokine storm-a hyper-inflammatory phenomenon-within hours of infection and the innate immune response. However, excess C5a can result in a pro-inflammatory environment orchestrated through a plethora of mechanisms that propagate lung injury, lymphocyte exhaustion, and an immune paresis. Furthermore, disruption of the homeostatic interactions between complement and extrinsic and intrinsic coagulation pathways contributes to a net pro-coagulant state in the microvasculature of critical organs. Fatal COVID-19 has been associated with a systemic inflammatory response accompanied by a pro-coagulant state and organ damage, particularly microvascular thrombi in the lungs and kidneys. Pathologic studies report strong evidence of complement activation. C5 blockade reduces inflammatory cytokines and their manifestations in animal studies, and has shown benefits in patients with aHUS, prompting investigation of this approach in the treatment of COVID-19. This review describes the role of the complement pathway and particularly C5a and its aberrations in highly pathogenic virus infections, and therefore its potential as a therapeutic target in COVID-19.

How I treat paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, clonal, complement-mediated hemolytic anemia with protean manifestations. PNH can present as a hemolytic anemia, a form of bone marrow failure, a thrombophilia, or any combination of the above. Terminal complement inhibition is highly effective for treating intravascular hemolysis from PNH and virtually eliminates the risk of thrombosis, but is not effective for treating bone marrow failure. Here, I present a variety of clinical vignettes that highlight the clinical heterogeneity of PNH and the attributes and limitations of the 2 US Food and Drug Administration-approved C5 inhibitors (eculizumab and ravulizumab) to treat PNH. I review the concept of pharmacokinetic and pharmacodynamic breakthrough hemolysis and briefly discuss new complement inhibitors upstream of C5 that are in clinical development. Last, I discuss the rare indications for bone marrow transplantation in patients with PNH.

Unrelated stem cell transplantation for severe acquired aplastic anemia: improved outcome in the era of high-resolution HLA matching between donor and recipient

BACKGROUND AND OBJECTIVES

Severe acquired aplastic anemia (SAA) is a potentially fatal bone marrow failure syndrome occurring mainly in children and young adults. Immunosuppressive regimens and hematopoietic stem cell transplantation (HSCT) are the only two available curative treatments. Patients who lack an HLA-identical sibling donor may receive HSCT from an unrelated donor, a strategy historically associated with high mortality rates. Thus, for patients refractory to immunosuppressive regimens, the decision to transplant stem cells from unrelated donors is weighed against supportive care and often represents a dilemma for physicians. We aimed to determine whether outcome after unrelated HSCT has improved in recent years and, if so, to determine the factors responsible for the improvement.

DESIGN AND METHODS

We analyzed the outcome of 89 patients (median age 17 years, range 0-52) with acquired SAA undergoing HSCT from an unrelated donor between 1989 and 2004. Cases were consecutively reported to the French Registry (SFGM-TC) by 25 centers.

RESULTS

Patients transplanted during two successive time-periods (1989-1998 and 1999-2004) had different 5-year survival probabilities (+/-95% confidence interval): 29%+/-7% and 50%+/-7%, respectively (p<0.01). The main difference between the two cohorts concerned HLA matching between donors and recipients at the allelic level for the ten HLA-A, -B, -C, -DRB1 and -DQB1 antigens, which was more frequent in 1999-2004 than in the former period (p=0.0004). In multivariate analysis, the only two factors affecting survival were HLA allelic matching (p<0.01) and younger age of recipient (17 pounds sterling years, p<0.0001). Survival reached 78%+/-11% at 5 years for the younger, fully HLA-matched patients.

INTERPRETATION AND CONCLUSIONS

Survival after unrelated HSCT for SAA has improved significantly over the past 15 years, mainly due to better HLA matching. Results for young patients who are fully HLA-matched at the allelic level with their donor are comparable to those observed after HSCT from a related donor.

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.

Multilineage glycosylphosphatidylinositol anchor-deficient haematopoiesis in untreated aplastic anaemia

Aplastic anaemia and paroxysmal nocturnal haemoglobinuria (PNH) are closely related disorders. In PNH, haematopoietic stem cells that harbour PIGA mutations give rise to blood elements that are unable to synthesize glycosylphosphatidylinositol (GPI) anchors. Because the GPI anchor is the receptor for the channel-forming protein aerolysin, PNH cells do not bind the toxin and are unaffected by concentrations that lyse normal cells. Exploiting these biological differences, we have developed two novel aerolysin-based assays to detect small populations of PNH cells. CD59 populations as small as 0.004% of total red cells could be detected when cells were pretreated with aerolysin to enrich the PNH population. All PNH patients displayed CD59-deficient erythrocytes, but no myelodysplastic syndrome (MDS) patient or control had detectable PNH cells before or after enrichment in aerolysin. Only one aplastic anaemia patient had detectable PNH red cells before exposure to aerolysin. However, 14 (61%) had detectable PNH cells after enrichment in aerolysin. The inactive fluorescent proaerolysin variant (FLAER) that binds the GPI anchors of a number of proteins on normal cells was used to detect a global GPI anchor deficit on granulocytes. Flow cytometry with FLAER showed that 12 out of 18 (67%) aplastic anaemia patients had FLAER-negative granulocytes, but none of the MDS patients or normal control subjects had GPI anchor-deficient cells. These studies demonstrate that aerolysin-based assays can reveal previously undetectable multilineage PNH cells in patients with untreated aplastic anaemia. Thus, clonality appears to be an early feature of aplastic anaemia.

Paroxysmal nocturnal haemoglobinuria clones in patients with myelodysplastic syndromes

Among acquired stem cell disorders, pathological links between myelodysplastic syndromes (MDS) and aplastic anaemia (AA), and paroxysmal nocturnal haemoglobinuria (PNH) and AA, have been often described, whereas the relationship between MDS and PNH is still unclear. We analysed blood cells of patients with MDS to determine the incidence of the PNH clone, and analysed the PIG-A gene to find mutations characteristic of the PNH clone in MDS. In four (10%) of 40 patients with MDS, flow cytometry showed affected erythrocytes and granulocytes negative for decay-accelerating factor (DAF) and CD59. The population of affected erythrocytes was smaller in MDS patients with PNH clone (MDS/PNH) than in patients with de novo PNH, and haemolysis was milder in the MDS/PNH patients. PIG-A mutations were found in granulocytes of all patients with MDS/PNH. In type and site, the PIG-A mutations were heterogeneous, similar to that observed in de novo PNH; i.e. no mutation specific to MDS/PNH was identified. Of note, three of four patients with MDS/PNH each had two PNH clones with different PIG-A mutations, suggesting that PIG-A is mutable in patients with MDS/PNH. In a MDS/PNH patient with trisomy 8, FISH detected a distinct karyotype in a portion of granulocytes with PNH phenotype, indicating that PNH and MDS partly shared affected cells. Thus, MDS predisposes to PNH by creating conditions favourable to the genesis of PNH clone. Considering the increasing prevalence and incidence of MDS, these disorders could be useful for investigating the mechanism by which PIG-A mutation is induced.

Paroxysmal nocturnal hemoglobinuria in Budd-Chiari syndrome: findings from a cohort study

BACKGROUND/AIMS

A well recognized cause of Budd-Chiari syndrome (BCS) is paroxysmal nocturnal hemoglobinuria (PNH). PNH is an acquired disorder of hematopoietic stem cells, characterized by intravascular hemolysis and venous thrombosis. Testing for this hematological disorder should be considered in all BCS patients.

METHODS

Using data from the EN-Vie study, a multi-center study of 163 patients with BCS, we investigated the relationship between BCS and PNH in 15 patients with combined disease and compared the results to 62 BCS patients in whom PNH was excluded.

RESULTS

Median follow-up for the study group (n=77) was 20 months (range 0-44 months). BCS patients with PNH presented with a significantly higher percentage of additional splanchnic vein thrombosis (SVT) as compared to BCS patients without PNH (47% vs. 10%, p=0.002). During follow-up, type and frequency of interventions for BCS was similar between both groups. Six patients with BCS and PNH were successfully treated with a transjugular intrahepatic portosystemic shunt (TIPS). Of 15 patients with PNH, six underwent allogenic stem cell transplantation after diagnosis of BCS. PNH was successfully cured in five cases. There was no significant difference in survival between BCS patients with and without PNH.

CONCLUSIONS

This study shows that despite a higher frequency of additional SVT, short-term prognosis of BCS patients with PNH does not differ from BCS patients without PNH. Treatment with TIPS can be safely performed in patients with PNH. Stem cell transplantation appears to be a feasible treatment option for PNH in BCS patients.

Outcome of pregnancy and disease course among women with aplastic anemia treated with immunosuppression

BACKGROUND

Aplastic anemia may develop during pregnancy and sometimes improves spontaneously after delivery. The effects of pregnancy on aplastic anemia after immunosuppressive treatment and of aplastic anemia on the outcome of pregnancy have not been described.

OBJECTIVE

To determine the outcome of pregnancy and the disease course among women with aplastic anemia who received immunosuppressive therapy.

DESIGN

Retrospective multicenter study.

SETTING

Twelve centers participating in the European Group for Blood and Marrow Transplantation.

PATIENTS

36 women who received immunosuppressive therapy to treat aplastic anemia.

MEASUREMENTS

Outcomes of pregnancy and aplastic anemia and blood counts before, during, and after delivery.

RESULTS

The 36 pregnancies resulted in 34 live births (one set of twins), 2 elective abortions, and 1 spontaneous abortion. Of the 36 pregnancies, 22 were uncomplicated and 14 involved medical complications. Seven pregnancies (19%) were complicated by relapse of aplastic anemia, and 5 patients without relapse (14%) needed transfusions during delivery. After delivery, 3 of the 7 patients who had relapse recovered spontaneously and 3 recovered after retreatment. One patient who did not respond to treatment died of aplastic anemia. A woman with aplastic anemia and paroxysmal nocturnal hemoglobinuria had a fatal cerebral thrombosis after delivery. Women with uneventful pregnancies had better prepregnancy remission status (8 complete and 11 partial remissions) and a higher median platelet count (146 x 10(9) cells/L) than did women with complicated pregnancies (2 complete remissions, 8 partial remissions, and 4 cases of paroxysmal nocturnal hemoglobinuria; median platelet count, 92 x 10(9) cells/L).

CONCLUSIONS

Successful pregnancy with normal outcome is possible in women with aplastic anemia previously treated with immunosuppression. Complications appear to be more likely in patients with low platelet counts and paroxysmal nocturnal hemoglobinuria-associated aplastic anemia.

The receptor for urokinase plasminogen activator is present in plasma from healthy donors and elevated in patients with paroxysmal nocturnal haemoglobinuria

The urokinase plasminogen activator (uPA) is a proteolytic enzyme which converts the proenzyme plasminogen to the active serine protease plasmin. A cell surface receptor for uPA (uPAR) is attached to the cell membrane by a glycosyl-phosphatidylinositol anchor. Binding of uPA to uPAR leads to an enhanced plasmin formation and thereby an amplification of pericellular proteolysis. We have shown previously that uPAR is expressed on normal blood monocytes and granulocytes, but is deficient on affected blood monocytes and granulocytes in patients with paroxysmal nocturnal haemoglobinuria (PNH), and that uPAR is present in plasma from these patients. In this study a newly established sensitive enzyme-linked immunosorbent assay (ELISA) has been applied for quantitation of uPAR in plasma. Unexpectedly, we found that uPAR is not only present in PNH plasma but also in plasma from healthy individuals. In 39 healthy individuals the mean plasma-uPAR value +/- SD was 31 +/- 15 pM, median 28 (range 11-108), and the corresponding value for six PNH patients was 116 +/- 67 pM, median 90 (range 61-228). The elevated uPAR-level in PNH patients was highly significant (Mann-Whitney test; P < 0.0001), and may possibly contribute to the propensity for thrombosis in PNH by inhibition of the fibrinolytic system. Binding of pro-uPA by uPAR in plasma may interfere with the appropriate binding of pro-uPA to cell-bound uPAR and therefore inhibit cell-associated plasmin generation and fibrinolysis. It is likely that the uPAR in normal plasma reflects the overall level of activity of the uPAR-mediated cell surface proteolysis. The present ELISA may be used for studies of uPAR levels in plasma from patients with conditions in which this activity might be increased, such as cancer and inflammatory disorders. Future studies will determine if uPAR in plasma is a parameter of clinical importance in these diseases.

Activated platelets in paroxysmal nocturnal haemoglobinuria

One of the major causes of morbidity and mortality in paroxysmal nocturnal haemoglobinuria (PNH) is venous thrombosis. We have studied fibrinolysis, coagulation and platelets in 11 patients with PNH in an attempt to identify the possible mechanism(s) of thrombosis in PNH. In this study we did not identify any fibrinolytic defects, evidence of coagulation activation, nor reduction in coagulation inhibitors. In contrast, in this cohort of 11 PNH patients we have identified varying degrees of platelet activation as defined by the surface expression of activation-dependent proteins and the binding of adhesive proteins to the platelet surface. The thrombotic events in PNH usually occur in the venous system. Our studies and previous experimental studies suggest that anti-platelet therapy may be efficacious in reducing the incidence and severity of venous thrombosis in PNH.

Late clonal complications in severe aplastic anemia

One hundred and seventy patients with severe aplastic anemia (SAA) were treated in Basel, from 1976 to 1992. Forty one underwent bone marrow transplantation (BMT) and 129 antilymphocyte globulin (ALG) therapy. As of January 1, 1993, 99 of the 170 patients are alive (58% +/- 7%) and the probability to be alive at 15 years is 54% +/- 4%. Until now, 29 patients have developed a clonal complication. All occurred within the ALG group. Nine patients developed a myelodysplastic syndrome (MDS), 16 patients paroxysmal nocturnal hemoglobinuria (PNH) and 4 patients both, PNH and MDS. The cumulative risk of developing a clonal complication after ALG-therapy is 42% +/- 13% at 15 years; for MDS this risk is 26% +/- 8% and for PNH 25% +/- 5%. The development of a clonal disease directly affects long term prognosis. The survival of the patients with stable disease is 81% +/- 10% and 36% +/- 13% for those with clonal evolution (p = 0.001). The most important risk factor is the type of treatment. In contrast to patients treated with ALG, none of the patients treated with BMT developed MDS or PNH (p < 0.001). No other clinical parameter, such as age, sex, etiology of SAA, severity of the disease and splenectomy correlate with an increased risk of developing this complication. In contrast, morphological parameters at the time of diagnosis, during bone marrow regeneration and at remission are indications in this respect.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanisms and clinical implications of thrombosis in paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare acquired disease characterized by a clone of blood cells lacking glycosyl phosphatidylinositol (GPI)-anchored proteins at the cell membrane. Deficiency of the GPI-anchored complement inhibitors CD55 and CD59 on erythrocytes leads to intravascular hemolysis upon complement activation. Apart from hemolysis, another prominent feature is a highly increased risk of thrombosis. Thrombosis in PNH results in high morbidity and mortality. Often, thrombosis occurs at unusual locations, with the Budd–Chiari syndrome being the most frequent manifestation. Primary prophylaxis with vitamin K antagonists reduces the risk but does not completely prevent thrombosis. Eculizumab, a mAb against complement factor C5, effectively reduces intravascular hemolysis and also thrombotic risk. Therefore, eculizumab treatment has dramatically improved the prognosis of PNH. The mechanism of thrombosis in PNH is still unknown, but the highly beneficial effect of eculizumab on thrombotic risk suggests a major role for complement activation. Additionally, a deficiency of GPI-anchored proteins involved in hemostasis may be implicated.