Paroxysmal Nocturnal Haemoglobinuria in Aplastic Anaemia

Cerebral Ischemic Infarction in Paroxysmal Nocturnal Hemoglobinuria

BACKGROUND

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal stem cell disorder, leading to a deficient biosynthesis of surface proteins in hematopoetic cells. Clinical symptoms consist of various combinations of intravascular hemolysis, bone marrow failure and mainly venous thrombotic events. Arterial thrombosis has been described only in a few cases.

METHODS

We report two patients with fatal ischemic strokes in PNH caused by arterial occlusion. In addition we also reviewed 7 previously reported cases in the literature and obtained follow-up information on 4 of the 5 survivors.

RESULTS

Both patients from our clinic had experienced hemoglobinuria and cytopenia prior to the vascular events but in one case diagnosis of PNH was only established after stroke onset. The causal role of PNH was supported by the absence of other vascular risk factors and by simultaneous symptoms of hemolysis and cytopenia. The diagnosis of PNH was confirmed by a positive result in flow cytometry. Despite extended therapeutic interventions, including antithrombotic treatment (with heparin or tirofiban) and decompressive hemicraniectomy both patients developed further thrombotic complications. The two patients died during their hospital stay from vascular or infectious complications. A review of all 9 published cases revealed that four patients died within a few weeks after the initial thrombotic event. No difference in treatment between patients with good or bad outcome was seen.

CONCLUSIONS

PNH is a rare cause of arterial stroke but it should be considered in young stroke patients with abnormal blood findings. As yet, there is no effective antithrombotic treatment.

Clonal evolution of aplastic anaemia to myelodysplasia/acute myeloid leukaemia and paroxysmal nocturnal haemoglobinuria

Aplastic anaemia (AA) is a non-malignant haemopoietic disorder characterised by peripheral blood pancytopenia and a hypocellular bone marrow. Successful management of acquired AA including treatment with immunosuppressive agents, mainly antithymocyte globulin (ATG) and cyclosporin or allogeneic haemopoietic stem cell transplantation, has resulted in long-term survival of many patients. The later evolution of complicating clonal disorders such as paroxysmal nocturnal haemoglobinuria, myelodysplasia and acute myeloid leukaemia in patients treated with immunosuppressive therapy may be a manifestation of the natural history of the aplasia, the development of which may or may not be increased by immunosuppressive therapy. A persistent, profound deficiency and/or defect in the stem cell compartment, despite haematological recovery after immunosuppressive therapy, may create an unstable situation which predisposes to later clonal disorders. A review of the progression of AA to clonal disorders is now outlined.

Absence of N-RAS point mutations in peripheral blood cells of patients with aplastic anaemia and paroxysmal nocturnal haemoglobinurea

The myelodysplastic syndromes (MDS) have a significant frequency of evolution into acute myeloid leukaemia (AML). Approximately 30% of MDS patients show activating mutations of the N-RAS proto-oncogene, and these patients are at increased risk of leukaemic evolution. Long-term survivors of aplastic anaemia (AA) and paroxysmal nocturnal haemoglobinurea (PNH) are also at significant risk of developing AML. We have screened peripheral blood DNA from 42 AA patients and 15 PNH patients for the presence of N-RAS point mutations. No mutations were detected in these samples, indicating that the mechanisms of evolution into AML may be different from those in MDS.

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)

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.

Paroxysmal nocturnal hemoglobinuria with onset in childhood and adolescence

BACKGROUND

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal hematologic disorder characterized by hemoglobinuria, thrombosis, infection, and a tendency toward bone marrow aplasia. Onset usually occurs in adulthood. Few children and adolescents with PNH have been described, and data on diagnosis, clinical course, and survival in young patients are unavailable.

METHODS

We retrospectively reviewed clinical and laboratory data on all patients 21 years old or younger in whom PNH had been diagnosed at Duke University Medical Center from 1966 to 1991.

RESULTS

Medical records and clinical follow-up data were available for 26 young patients. Although 50 percent of adult patients present with hemoglobinuria, only four of our patients (15 percent) presented with this feature. In contrast, 15 of our patients (58 percent) had moderate or severe bone marrow failure at presentation, as compared with about 25 percent of adults in cases from the literature; all 26 patients eventually had evidence of bone marrow dysfunction. Eight patients (31 percent) have died, with a median survival of 13.5 years since their initial symptoms.

CONCLUSIONS

Children and adolescents with PNH have a greater prevalence of bone marrow failure than do adults with this disorder, and their morbidity and mortality are high. Bone marrow transplantation should be considered for selected young patients with PNH.

Late haematological complications in severe aplastic anaemia

137 patients with severe aplastic anaemia (SAA) were treated in Basel from 1976 to 1986. 34 underwent bone marrow transplantation (BMT) and 103 received antilymphocyte globulin (ALG) therapy. We have analysed the incidence of late haematological complications in both groups of patients. 20 patients treated with ALG developed a late haematological complication. A myelodysplastic syndrome or frank leukaemia occurred in eight and paroxysmal nocturnal haemoglobinuria (PNH) in 13 patients. Nine of the 13 patients with PNH had clinical signs of haemolysis, four only had positive laboratory tests. One patient had PNH and acute leukaemia. The risk of developing a haematological complication increased continuously and reached 57% at 8 years. Neither PNH nor leukaemia occurred in patients treated with BMT. The increased survival rate and the long observation time after ALG therapy have revealed a new perspective of the prognosis of aplastic anaemia. Patients treated with BMT appear to be cured whereas those treated with ALG remain at risk for late complications.

Specific deposition of complement protein C3b on abnormal PNH erythrocytes permits their separation by partitioning. Possible general approach for isolation of specific cell populations

The deposition of complement proteins on a cell surface has previously been shown to reduce the cell's partition ratio in a two-polymer aqueous phase system. This phenomenon has now been extended to segregate, by partitioning, subpopulations of erythrocytes from patients with paroxysmal nocturnal hemoglobinuria (PNH). Purified components of the complement system were employed to deposit the protein C3b specifically on abnormal erythrocytes which lacked the membrane-associated complement regulatory protein DAF. As few as 2100 C3b/cell reduced the partition ratio and 24,000 C3b/cell resulted in resolution of the C3b-bearing and non-bearing human red cells. It was found that the proportion of cells separated did not equal the proportion of cells lysed by complement in the acidified serum lysis test when blood from three of the five patients was examined. The results indicate that the defect giving rise to DAF- cells may be, but is not necessarily, coexpressed with defects affecting other membrane-associated regulatory factors. A broader application of the method using monoclonal antibodies to direct purified complement components to specific cell populations should permit their isolation in large quantities.

Aplastic anemia: recent advances in pathogenesis and treatment

Successful bone marrow transplantation and bone marrow culturing techniques have generated a large body of research into the pathogenesis and treatment of aplastic anemia. Most prominent has been the emphasis on autoimmune mechanisms. Several etiologic types and diagnostic criteria are discussed, the evidence supporting immune and other mechanisms of pathogenesis is examined, and results of current therapeutic trials are addressed.