Refractory anaemia (Fanconi type): Its Incidence in Three Members of One Family, with in One Case a Relationship to Chronic Haemolytic Anaemia with Nocturnal Haemo-Globinuria (Marchiafava-Micheli Disease or `Nocturnal Haemoglobinuria')

The predictive value of PNH clones, 6p CN-LOH, and clonal TCR gene rearrangement for aplastic anemia diagnosis

Acquired aplastic anemia (AA) is a life-threatening bone marrow aplasia caused by the autoimmune destruction of hematopoietic stem and progenitor cells. There are no existing diagnostic tests that definitively establish AA, and diagnosis is currently made via systematic exclusion of various alternative etiologies, including inherited bone marrow failure syndromes (IBMFSs). The exclusion of IBMFSs, which requires syndrome-specific functional and genetic testing, can substantially delay treatment. AA and IBMFSs can have mimicking clinical presentations, and their distinction has significant implications for treatment and family planning, making accurate and prompt diagnosis imperative to optimal patient outcomes. We hypothesized that AA could be distinguished from IBMFSs using 3 laboratory findings specific to the autoimmune pathogenesis of AA: paroxysmal nocturnal hemoglobinuria (PNH) clones, copy-number-neutral loss of heterozygosity in chromosome arm 6p (6p CN-LOH), and clonal T-cell receptor (TCR) γ gene (TRG) rearrangement. To test our hypothesis, we determined the prevalence of PNH, acquired 6p CN-LOH, and clonal TRG rearrangement in 454 consecutive pediatric and adult patients diagnosed with AA, IBMFSs, and other hematologic diseases. Our results indicated that PNH and acquired 6p CN-LOH clones encompassing HLA genes have ∽100% positive predictive value for AA, and they can facilitate diagnosis in approximately one-half of AA patients. In contrast, clonal TRG rearrangement is not specific for AA. Our analysis demonstrates that PNH and 6p CN-LOH clones effectively distinguish AA from IBMFSs, and both measures should be incorporated early in the diagnostic evaluation of suspected AA using the included Bayesian nomogram to inform clinical application.

Paroxysmal Nocturnal Hemoglobinuria (Membrane Defect, Pathogenesis, Aplastic Anemia, Diagnosis)

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal disorder in which intravascular hemolysis results from the somatic mutation of the totipotent stem cells causing an intrinsic defect in red cell membrane. PNH cells lack glycosylphosphatidylinositol (GPI) anchored membrane proteins. Of these proteins absence of CD 59 (MIRL - membrane inhibitor of reactive lysis, protectin) and CD 55 (DAF - decay accelerating factor) makes the PNH cells abnormally sensitive to the lytic action of complement. The defect appears to be in the somatic mutation of the X-linked PIG-A (phosphatidylinositolglycan A class) gene which participate in an early step of GPI - anchor synthesis. PNH is characterized by recurrent life threatening venous thromboses and an intimate association with aplastic anemia (AA). It seems that PNH always coexists with bone marrow failure (BMF) (37). The possible explanation may be that some GPI-anchored proteins may be a critical target recognized by immune effector cells. PNH clones not possessing these critical GPI - anchored proteins will survive because they are selectively resistant to the autoimmune assault that eliminates most normal clones. The flow cytometry of erythrocytes using anti-CD 59 and anti-CD 59 and anti-CD 55 of granulocytes has been now introduced as a very sensitive and quantitative method of PNH diagnosis able to detect PNH cells even in normal individuals (1,54). Thus it seems now clear that we must make distinction between the detection of very occasional PNH cells in patients with BMF and PNH as a clinicohematological entity. Unfortunately, we do not know the minimal content of PNH cells required to produce clinical signs of PNH (38).

Sir John Dacie MD, FRS, FRCP, FRCPath

Prof. Sir John Dacie was one of the most distinguished haematologists of the 20th century. He died on 12 February 2005 at the age of 92. This annotation is intended to give an impression of his career, and his role in the development of haematology in the UK and beyond. It describes his approach to haematological practise, taking account of both clinical and laboratory aspects, and reviews his published works over a range of haematological topics.

Paroxysmal nocturnal hemoglobinuria arising from Fanconi anemia

The progress of a female child with African type Fanconi anemia that evolves in time into paroxysmal nocturnal hemoglobinuria is described. Modern diagnostic methods are used to confirm this process. A discussion of possible mechanisms ensues.

Bone marrow failure in Shwachman-Diamond syndrome does not select for clonal haematopoiesis of the paroxysmal nocturnal haemoglobinuria phenotype

Bone marrow failure is believed to be the underlying condition that drives the expansion of the paroxysmal nocturnal haemoglobinuria (PNH) clone. Indeed, circulating PNH blood cells have been identified in patients with acquired aplastic anaemia and with hypoplastic myelodysplasia. Whether PNH blood cells are also present in patients with inherited aplastic anaemia has not been reported. We screened a large group of patients diagnosed with Shwachman-Diamond Syndrome (SDS) for PNH blood cells. None of the patients analysed had detectable circulating PNH blood cells, indicating that bone marrow failure in SDS does not select for PNH progenitor cells.

Paroxysmal nocturnal haemoglobinuria: nature's gene therapy?

The development of paroxysmal nocturnal haemoglobinuria (PNH) requires two coincident factors: somatic mutation of the PIG-A gene in one or more haemopoietic stem cells and an abnormal, hypoplastic bone marrow environment. When both of these conditions are met, the fledgling PNH clone may flourish. This review will discuss the pathophysiology of this disease, which has recently been elucidated in some detail.

Glycosyl phosphatidylinositol (GPI)-anchored molecules and the pathogenesis of paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by the expansion of one or more clones of stem cells producing progeny of mature blood cells deficient in the plasma membrane expression of all glycosyl phosphatidylinositol (GPI)-anchored proteins (AP). This is due to somatic mutations in the X-linked gene PIGA, encoding one of the several enzymes required for GPI anchor biosynthesis. More than 20 GPI-APs are variously expressed on hematological cells. GPI-APs may function as enzymes, receptors, complement regulatory proteins or adhesion molecules; they are often involved in signal transduction. The absence of GPI-APs may well explain the main clinical findings of PNH, i.e., hemolysis and thrombosis in the venous system. Other aspects of PNH pathophysiology such as various degrees of bone marrow failure and the dominance of the PNH clone may also be linked to the biology and function of GPI-APs. Results of in vitro and in vivo experiments on embryoid bodies and mice chimeric for nonfunctional Piga have recently demonstrated that Piga inactivation confers no intrinsic advantage to the affected hematopoietic clone under physiological conditions; thus additional factors are required to allow for the expansion of the mutated cells. A close association between PNH and aplastic anemia suggests that immune system mediated bone marrow failure creates and maintains the conditions for the expansion of GPI-AP deficient cells. In this scenario, a PIGA mutation would render GPI-AP deficient cells resistant to the cytotoxic autoimmune attack, enabling them to emerge. Even though the 'survival advantage' hypothesis may explain all the various aspects of this intriguing disease, a formal proof of this theory is still lacking.

Natural history of paroxysmal nocturnal hemoglobinuria

BACKGROUND

Paroxysmal nocturnal hemoglobinuria (PNH), which is characterized by intravascular hemolysis and venous thrombosis, is an acquired clonal disorder associated with a somatic mutation in a totipotent hematopoietic stem cell. An understanding of the natural history of PNH is essential to improve therapy.

METHODS

We have followed a group of 80 consecutive patients with PNH who were referred to Hammersmith Hospital, London, between 1940 and 1970. They were treated with supportive measures, such as oral anticoagulant therapy after established thromboses, and transfusions.

RESULTS

The median age of the patients at the time of diagnosis was 42 years (range, 16 to 75), and the median survival after diagnosis was 10 years, with 22 patients (28 percent) surviving for 25 years. Sixty patients have died; 28 of the 48 patients for whom the cause of death is known died from either venous thrombosis or hemorrhage. Thirty-one patients (39 percent) had one or more episodes of venous thrombosis during their illness. Of the 35 patients who survived for 10 years or more, 12 had a spontaneous clinical recovery. No PNH-affected cells were found among the erythrocytes or neutrophils of the patients in prolonged remission, but a few PNH-affected lymphocytes were detectable in three of the four patients tested. Leukemia did not develop in any of the patients.

CONCLUSIONS

PNH is a chronic disorder that curtails life. A spontaneous long-term remission can occur, which must be taken into account when considering potentially dangerous treatments, such as bone marrow transplantation. Platelet transfusions should be given, as appropriate, and long-term anticoagulation therapy should be considered for all patients.

Venous thrombosis and splenic rupture in paroxysmal nocturnal hemoglobinuria

A patient with an 11 year history of paroxysmal nocturnal hemoglobinuria presented with severe abdominal pain. On admission, the hematocrit value was 30 per cent and unchanged from repeated measurements during the previous three years. Abdominal angiography identified extensive thromboses of the splenic and portal venous systems. After initial improvement on heparin therapy, the patient experienced additional abdominal crises. A ruptured and multifragmented spleen was removed at the time of exploratory laparotomy. Postoperatively, after a several days' interval of improvement, the patient experienced additional thrombotic episodes of the abdomen, upper extremities and cerebral cortex. The latter was associated with disabling nerve paralysis. With continuous intravenous heparin plus steroid therapy, the patient's condition improved progressively. Despite the numerous thrombotic episodes during the prolonged hospital course, no hemolytic episodes were observed. This is the first report of documented splenic rupture in a patient with paroxysmal nocturnal hemoglobinuria.

Formal genetics of Fanconi's anemia

The formal genetics of Fanconi's anemia were investigated on the basis of 21 families from different European countries, and of 69 families from the literature.

CONCLUSIONS

1. The result of segregation analysis is compatible with the hypothesis of a simple autosomal recessive mode of inheritance. 2. The number of sporadic cases is not greater than expected. 3. Among the affected siblings in the sibships analyzed, males are somewhat more frequent than females. However, this sex difference is also found among the unaffected siblings, and it is not statistically significant. 4. Contrary to assertions made in the literature, there is no clustering of affected in the sequence of siblings, no maternal age effect, and no preference of higher birth orders. 5. A high intrafamilial correlation for age at onset, and (very probably) number and severity of malformations points to genetic heterogeneity. Apart from the standard type, an especially mild type with late onset, few malformations, and a relatively benign course seems to exist. Its counterpart is possibly an especially severe type with early onset, many malformations, and a malignant course. However, definite conclusions on the special character of this heterogeneity will require application of additional methods.

Congenital Hypoplastic Anaemia: Report of Two Cases

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Pancytopenia with Congenital Defects (Fanconi's Anaemia)

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The value of splenectomy in Fanconi's anaemia

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[Constitutional pathology of erythropoiesis]

The concept and definition of constitutional pathology. Genetic erythropathies such as constitutional spherocytosis, leptocytosis, ovalocytosis and drepanocytosis and their relation to hemolytic clinical syndromes are discussed. Sickle cell trait, sickle cell anemia, and sickle cell disease have to be distinguished as clinical manifestations of drepanocytosis. They represent a special variety of a « status degenerativus » (Bauer). Four genetic types of human hemoglobin have so far been identified that differ from each other by their molecular architecture and chemical reactivity. Several constitutional abnormalities of erythropoiesis other than those just mentioned are discussed: a hereditary defect in hemoglobin synthesis; erythroid multinuclearity; acanthocytosis; Fanconi's syndrome of hypoplasia and abiotrophy of the bone marrow as another variety of a status degenerativus.

Erythrogenesis imperfecta

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