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

Severe Aplastic Anemia Manifesting After Complete Remission of Acute Promyelocytic Leukemia: Is it a Fortuitous Association?

Acute leukemia, secondary myelodysplasia and paroxysmal nocturnal hemoglobinuria evolving from severe aplastic anemia (AA) following immunosuppressive therapy are well recognized. However, severe AA occurring after complete remission of acute promyelocytic leukemia (APL) has been documented only once in 2009. We report a case of 30-year-old male diagnosed with APL who achieved complete cytogenetic remission with all-trans retinoic acid based induction regimen and developed severe AA few months later during maintenance therapy.

Evolution Of Clonal Cytogenetic Abnormalities in Aplastic Anemia

Prior to the introduction of effective therapies, the high mortality rates of severe aplastic anemia (AA) precluded recognition of late complications of this disease. Once the survival of AA improved, observation of clonal evolution raised questions as to whether the development of secondary myelodysplastic syndrome (MDS) is a part of the extended natural history of the disease or is related to the therapies applied. Clinical features of myelodysplasia and AA can overlap, and typical MDS may evolve as a complication of AA. Common pathophysiologic elements operate in these diseases and are subject to many studies and theories as to what mechanisms in AA may lead to the late evolution of MDS. Similarly, AA has been hypothesized to be a reflection of an over-reactive immune response triggered by the appearance of genetically altered and/or phenotypically abnormal dysplastic clones. Hypocellular variants of myelodysplasia and responsiveness of certain forms of MDS to immunosuppressive regimens serve as the most appealing examples of the intricate and close pathophysiologic relationship of this disease with AA. The diagnosis of clonal evolution in the course of AA can be obvious if secondary cytopenia involves hypercellularity and a high percentage of blasts. In addition, the occurrence of a new karyotypic defect objectively heralds the progression of disease to MDS. However, the diagnostic imprecision of dysplasia recognition in the context of marrow hypocellularity, inability to obtain informative cytogenetics, and a high proportion of MDS cases with normal karyoptype have hampered studies designed to determine the frequency and timing of MDS evolution in AA. In addition, the diagnostic criteria and definitions used are not unified. While some centers recognize that the abnormal karyotype does not preclude the diagnosis of AA; in others, the diagnosis of AA includes the presence of normal karyoptype. Many typical features of dysplastic evolution in AA have been clarified. For example, karyotypes most frequently encountered in MDS secondary to AA involve chromosomes 6, 7 and 8. The evolution rates seem to be in the range of 10-15% in 10 years, but there are no predictive clues as to which patients are at greatest risk for this complication. Study of the mechanisms of clonal evolution in AA may help understand the pathophysiology of other forms of MDS and leukemia and also the mechanisms of antileukemic surveillance. Clinically, identification of patients at increased risk for clonal complications may influence the choice of therapies applied.

Cord Blood-Derived Plasma Factor (CBPF) Potentiates the Low Cytokinetic and Immunokinetic Profile of Bone Marrow Cells in Pesticide Victims Suffering from Acquired Aplastic Anaemia (AAA): An in vitro Correlate

Cases of Acquired Aplastic Anaemia (AAA) in patients with a long history of pesticide exposure from agricultural fields have been investigated in our laboratory using an immunological approach. These patients showed moderate to severe degrees of bone marrow aplasia as a result of 9-12 years protracted exposure to pesticides which were mainly comprised of organophosphorous and organochloride compounds. The bone marrow aspirate culture was found to be severely deficient both in terms of differentiation and proliferation, and cell mediated immune function (CMI). We attempted ex vivo manipulation of the bone marrow population of patients in two different protocols: in one, stem cell factor (SCF), interleukin-3 (IL-3), and granulocyte-colony stimulating factor (G-CSF) were administered and, in the second set, cord blood-derived plasma factors (CBPF) were supplemented to evaluate the effects, if any. Simultaneously, two control groups including one for healthy normal control (N) and the second, for non-pesticide induced aplastic anaemia group of patients (NPAA) was also investigated for all the above parameters. Active colony formation and improved cellular immune activity (CMI) was observed more frequently in the CBPF treated group rather than that in the cytokine treated group. Surprisingly, administration of cytokines in the first set and CBPF in the second set triggered CD34 (+) cell generation as revealed through flow cytometric analysis (FACS). The effect was more pronounced in the second set. Investigations carried out with NPAA showed relatively insignificant effects with both cytokine and CBPF set up. The investigations indicated that AAA as induced by pesticides could be therapeutically manipulated by exogenous cytokines and growth factors and, more efficiently, by CBPF by way of immunopotentiation through microenvironmental supplementation.

Further development of a model of chronic bone marrow aplasia in the busulphan-treated mouse

Aplastic anaemia (AA) in man is an often fatal disease characterized by pancytopenia of the peripheral blood and aplasia of the bone marrow. AA is a toxic effect of many drugs and chemicals (e.g. chloramphenicol, azathioprine, phenylbutazone, gold salts, penicillamine and benzene). However, there are no widely used or convenient animal models of drug-induced AA. Recently, we reported a new model of chronic bone marrow aplasia (CBMA = AA) in the busulphan (BU)-treated mouse: eight doses of BU (10.50 mg/kg) were administered to female BALB/c mice over a period of 23 days; CBMA was evident at day 91/112 post-dosing with significantly reduced erythrocytes, platelets, leucocytes and nucleated bone marrow cell counts. However, mortality was high (49.3%). We have now carried out a study to modify the BU-dosing regime to induce CBMA without high mortality, and investigated the patterns of cellular responses in the blood and marrow in the post-dosing period. Mice (n = 64/65) were dosed 10 times with BU at 0 (vehicle control), 8.25, 9.0 and 9.75 mg/kg over 21 days and autopsied at day 1, 23, 42, 71, 84, 106 and 127 post-dosing (n = 7-15); blood and marrow samples were examined. BU induced a predictable bone marrow depression at day 1 post-dosing; at day 23/42 post-dosing, parameters were returning towards normal during a period of recovery. At day 71, 84, 106 and 127 post-dosing, a stabilized, late-stage, nondose-related CBMA was evident in BU-treated mice, with decreased erythrocytes, platelets and marrow cell counts, and increased MCV. At day 127 post-dosing, five BU-treated mice showed evidence of lymphoma. In this study, mortality was low, ranging from 3.1% (8.25 mg/kg BU) to 12.3% (9.75 mg/kg BU). It is concluded that BU at 9.0 mg/kg (or 9.25 mg/kg) is an appropriate dose level to administer (10 times over 21 days) to induce CBMA at approximately day 50-120 post-dosing.

Flow cytometric evaluation of circulating CD34 + cell counts and apoptotic rate in children with acquired aplastic anemia and myelodysplasia

OBJECTIVE

Identification of a rapid and noninvasive test for the follow-up of aplastic anemia (AA) patients during immunosuppressive therapy (IST) to evaluate its functional effect on hematopoietic progenitors (HPC) and for early detection of progression to myelodysplasia or relapse.

MATERIALS AND METHODS

Absolute count and apoptotic rate (AR) of peripheral blood (PB) CD34+ cells were evaluated by three-color flow cytometry for CD45, CD34, and annexin V in cord blood (CB), normal children, and adults, as well as in pediatric patients with AA at diagnosis and during IST, Fanconi anemia (FA), chronic immune cytopenia, and refractory anemia with excess blasts (RAEB).

RESULTS

In normal subjects, the AR of PB CD34+ cells showed a progressive increase (p < 0.05), while their counts decreased (p < 0.05) from birth to adulthood. In very severe AA (vSAA) and severe AA (SAA) at diagnosis, the AR was 91.6% +/- 2.8%, higher than controls (p < 0.05), and PB CD34+ cell count was 2.6 +/- 2.4/microL. In FA patients, the PB CD34+ AR was again significantly increased (54.2% +/- 13.7%) with an absolute count of 3.7 +/- 1.2/microL. Conversely, in RAEB the AR was 11.7% +/- 3.5% and the absolute count 85.1 +/- 48.2/microL (p < 0.05). Chronic immune cytopenias did not significantly differ from controls.

CONCLUSIONS

Flow cytometry evaluation of PB CD34+ AR and counts is a noninvasive and feasible first-step method for the differentiation of AA and myelodysplasia (MDS), and it might be useful for monitoring AA during IST to secure the early detection of relapse or transformation to MDS.

Allogeneic CD34-enriched peripheral blood stem cell transplantation in a patient with paroxysmal nocturnal haemoglobinuria

Paroxysmal nocturnal haemoglobinuria (PNH) is an acquired clonal disorder of haematopoietic stem cells associated with a somatic mutation in the phosphatidylinositol glycan complementation class A (PIG-A) gene. The only curative option is an allogeneic stem cell transplant (SCT), although treatment is hazardous. A 46-year-old male patient with PNH and obvious signs of severe, progressive haemolysis was transplanted in July 2002 with highly purified CD34 T-cell depleted peripheral blood stem cells from his HLA-identical brother. Prior to transplantation, the PNH was resistant to immunosuppressive therapy. The patient received 6.1 x 10(6)/kg bodyweight CD34-positive cells with a proportion of CD3-positive cells of 0.81 x 10(4)/kg bodyweight. After engraftment, 12 days post transplant (neutrophils>1.0/nl) the patient's physical condition steadily improved and parameters of haemolysis decreased. No glycophosphatidylinositol-deficient cells in peripheral blood could be detected by flow cytometry 40 and 100 days after transplant. We conclude that PNH may be cured by allogeneic CD34-enriched SCT from a sibling donor attempting to avoid acute GVHD and to reduce cumulative organ toxicity by using this transplantation modality.

A new model of busulphan-induced chronic bone marrow aplasia in the female BALB/c mouse

Aplastic anaemia (AA) is characterized by hypocellular marrow, pancytopenia, and risk of severe anaemia, haemorrhage and infection. AA is often idiopathic, but frequently occurs after exposure to drugs/chemicals. However, the pathogenesis of AA is not clearly understood, and there are no convenient animal models of drug-induced AA. We have evaluated regimens of busulphan (BU) administration in the mouse to produce a model of chronic bone marrow aplasia showing features of human AA. Mice were given 8 doses of BU at 0, 5.25 and 10.50 mg/kg over 23 days; marrow and blood samples were examined at 1, 19, 49, 91 and 112 days after dosing. At day 1 post dosing, in mice treated at 10.50 mg/kg, nucleated marrow cells, CFU-GM and Erythroid-CFU were reduced. Similarly, peripheral blood erythrocytes, leucocytes, platelets and reticulocytes were reduced. At day 19 and 49 post dosing, there was a trend for parameters to return towards normal. However, at day 91 and 112 post dosing, values remained significantly depressed, with a stabilized chronic bone marrow aplasia. At day 91 and 112 post dosing, marrow cell counts, CFU-GM and Erythroid-CFU were decreased; marrow nucleated cell apoptosis and c-kit+ cell apoptosis were increased; peripheral blood erythrocyte, leucocyte, and platelet counts were reduced. We conclude that this is a model of chronic bone marrow aplasia which has many interesting features of AA. The model is convenient to use and has potential in several areas, particularly for investigations on mechanisms of AA pathogenesis in man.

Stem cell transplantation for paroxysmal nocturnal haemoglobinuria in childhood

Paroxysmal nocturnal haemoglobinuria (PNH) is a clonal haematopoietic disorder characterized by chronic or intermittent intravascular haemolysis, variable cytopenia and an increased risk of thrombosis. Stem cell transplantation (SCT) is a curative therapeutic option, but its risks must be carefully weighed against the natural course of PNH. World-wide experience with SCT for PNH in the paediatric age group is scarce. We report on two adolescents suffering from PNH with life-threatening complications who were successfully transplanted from unrelated donors. Indications and techniques of SCT in childhood PNH are discussed and an overview of the literature is given.

Current knowledge on the pathophysiology of Fanconi anemia: from genes to phenotypes

Fanconi anemia (FA) is an autosomal recessive disease characterized by congenital anomalies, bone marrow failure, and leukemia susceptibility. FA cells show chromosome instability and hypersensitivity to DNA cross-linking agents such as mitomycin C. Recent studies indicate that there are at least 8 genetically distinct FA groups (A, B, C, D1, D2, E, F, G). To date, 6 genes (for A, C, D2, E, F, and G) have been cloned. In this review, we describe the structures and functions of FA proteins. Increasing evidence indicates that the multiple FA proteins cooperate in a biochemical pathway and/or a multimer complex. FANCD2, a downstream component of the FA pathway, has recently been shown to be ubiquitinated in response to DNA damage and to translocate to nuclear foci containing BRCA1, a breast cancer susceptibility gene product, suggesting a role for this protein in DNA repair functions. We also describe 2 emerging issues: genotype-phenotype relationships and mosaicism. The FA pathway is likely to play a critical role as a caretaker of genomic integrity in hematopoietic stem cells. Clarifying the molecular basis of this disease may provide new insights into the pathogenesis of bone marrow failure syndromes and myeloid malignancies.

T-Cell Type Acute Lymphoblastic Leukemia Following Cyclosporin A Therapy for Aplastic Anemia

Cyclosporin A (CsA) is used to prevent rejection in transplantation and to treat autoimmune and hematologic diseases such as aplastic anemia. However, the tumor growth-promoting effect of CsA remains controversial. We report the case of a 24-year-old man who developed acute lymphoblastic leukemia of precursor-T-cell origin after 75 months of treatment with CsA for aplastic anemia. The surface antigen phenotype of his leukemic cells was CD2+, CD3+, CD5+, CD7+, CD4-, CD8-, CD10-, CD20-, CD34-, CD41-, and CD56-. Southern blot analysis revealed a monoclonal rearrangement of T-cell receptor-Jgamma nongermline fragments in HindIII digestion.

Three cases of typical aplastic anaemia associated with a Philadelphia chromosome

We report three cases of typical aplastic anaemia (AA) associated with a Philadelphia chromosome. This translocation was detected at the time of diagnosis of AA (one patient) and when overt leukaemia was diagnosed (two patients: one chronic myeloid leukaemia and one acute lymphoblastic leukaemia) after AA therapy and recovery of blood counts. We discuss the literature arguments about considering some cases of AA as preleukaemic disorders and suggest that our cases illustrate the association of AA with a clonal malignant disorder. We conclude that cytogenetic analysis is necessary at diagnosis of AA or after recovery of blood counts.

Bone marrow failure in children with acute liver failure

BACKGROUND

Aplastic anemia is a rare but well-recognized complication of acute hepatitis and acute liver failure. The cause is unknown, and the condition is fatal without bone marrow recovery. Treatment includes immunosuppression regimens or bone marrow transplantation. The purpose of this study was to investigate the incidence, cause, treatment, and outcomes of this disorder in children.

METHODS

Retrospective chart review of 75 patients with acute liver failure in a major pediatric liver center.

RESULTS

Eight patients had evidence of bone marrow failure. Of those, six had aplastic anemia, and two had transient bone marrow suppression. There were five boys, median age 57 months (range, 36-132 months). Two had parvovirus B19, six had non-A, non-B, non-C hepatitis. Five underwent liver transplantation: auxiliary in one, orthotopic in four. The interval between initial symptoms and development of aplastic anemia and/or bone marrow suppression was 21 to 99 days (median, 39 days). Four patients with aplastic anemia received intravenous antithymocyte globulin (ATG) or antilymphocyte globulin (ALG). Median recovery period of granulopoiesis was 62 days (range, 27-115 days). Two made a full recovery, one had myelodysplasia, and one with unresponsive disease died of septic complications. Four did not receive ATG/ALG, two had aplastic anemia, and two had bone marrow suppression. Three underwent liver transplantation, and all four resumed granulopoiesis. One child who underwent liver transplantation died of sepsis with chronic rejection. Median recovery of granulopoiesis was 99 days (range, 20-153 days).

CONCLUSIONS

Bone marrow failure occurs in 10.7% of children with acute liver failure. It sometimes occurs in association with non-A, non-B, non-C hepatitis and parvovirus B19 infection. Treatment with ATG/ALG is successful and is well tolerated in most cases.

Myelodysplasia

The epidemiology of myelodysplasia, or myelodysplastic syndrome (MDS), is in evolution. As populations are aging and therapies for cancer are improving, the frequency of this disease is increasing. Recent population surveys and case-control studies are reviewed. Knowledge of the molecular pathogenesis and pathophysiology of MDS is advancing at a remarkable pace and new information on molecular events is presented. The treatment of MDS is complex and highly individualized. Although many patients are older and may have significant co-morbid disease or poor performance status, there are curative options with allogeneic transplantation for selected patients. The recent transplant publications are reviewed. Other investigative treatment approaches, including the use of new chemotherapy agents, growth factor combinations, and antithymocyte globulin appear promising and are reviewed.