Sequential development of distinct clonal chromosome abnormalities in a patient with preleukaemia

Myelodysplastic syndromes in childhood--classification, epidemiology, and treatment

Much of the applied terminology of myelodysplastic syndromes (MDS) in childhood is confusing and not mutually exclusive. It is therefore proposed that the FAB classification of MDS is used in children in order to improve diagnostic precision and to facilitate epidemiologic, clinical, and therapeutic comparisons. The true incidence of childhood MDS is unknown but the rate may approximate the incidence of acute myelogenous leukemia. A pooled analysis of eight larger series representing 110 children less than 15 years old at diagnosis with de novo MDS classified according to the FAB recommendations showed that the more aggressive subtypes dominated, which partly may reflect that the less advanced cases are underdiagnosed. The median age at presentation was 6.0 years. The male/female ratio was 1.6. Monosomy 7 was the most frequent cytogenetic abnormality. The median survival was 13 months and the probability of survival three years from diagnosis was 16%. Spontaneous remission may be observed very infrequently. Allogeneic bone marrow transplantation (BMT) represents the only potentially curative treatment. The survival rate three years after BMT is about 50%. Major differences between childhood and adult MDS exist with respect to the distribution of FAB subgroups, the rate of progression, and the cytogenetic findings. The literature on MDS in children is still sparse and there is an obvious need for more studies designed to determine the incidence, clinical and laboratory characteristics, the natural course, and the efficacy of contemporary treatment options.

Translocations involving 12p in acute myeloid leukemia: association with prior myelodysplasia and exposure to mutagenic agents. United Kingdom Cancer Cytogenetics Group (UKCCG)

Six cases of acute myeloid leukemia (AML) with translocations involving 12p are described. The patients were one child age 7 yrs and five adults with an age range of 20-66 yrs (median 46 yrs). In two patients AML followed treatment for acute lymphoblastic leukemia (ALL), in one case after 11 years disease-free survival. Of the remaining four patients, two had been occupationally exposed to possible mutagens and three had a previous myelodysplastic phase. Two patients achieved complete remission; survival for the six cases was between 1 and 24 months (median 6.5 months). The breakpoints in 12p occurred in p11, p12, and p13, indicating that several sites are important in these rearrangements, and it is suggested that t(12;17)(p11;q11) is a new nonrandom abnormality in AML.

Myelodysplastic syndromes (refractory anemia). A perspective of the biologic, clinical, and therapeutic issues

The myelodysplastic syndromes (MDS) are a diverse group of hematologic disorders that have an abnormality in differentiation of the hematopoietic stem cell resulting in varying degrees of peripheral blood cytopenias. The author reviews the hematologic and clinical aspects of MDS, summarizes the recent pertinent aspects of the advances in our understanding of the disease, and explores the current approaches in the new treatment programs.

Do random (non-clonal) chromosome abnormalities in bone marrow predict a clone to come? Southwestern Oncology Group of Leukemia Cytogenetics Subcommittee

The biologic significance of clonal karyotypic abnormalities in human neoplasms is becoming better understood, but the significance of rare chromosomal aberrations is uncertain. Useful, yet arbitrary, cytogenetic definitions of a clone have been established and cases with a frequency of chromosome aberrations less than the accepted convention are explained by random loss, karyotypic instability/evolution, or other technical artifact. Are non-clonal chromosomal abnormalities that may predict future clinically significant clones being ignored? A brief case report is presented raising two such issues in the same myelodysplastic patient. This child had monosomy 7 and, later, trisomy 8, as well as increased numerical/structural aberrations seeming to predict relapse. Preliminary data from the Southwestern Oncology group is also presented. Non-clonal data should be included, when appropriate, in the clinical report.

Spontaneous remission in myelodysplastic syndrome. A case report

A patient with refractory anemia with excess blasts (RAEB) and pancytopenia is reported. He was red blood cell (RBC)-transfusion dependent. Karyotype analysis showed a complex cytogenetic abnormality consisting of loss of chromosome 7 and trisomy 8. Without cytotoxic treatment, his complete blood count (CBC) subsequently became normal. He is no longer transfusion dependent and repeat cytogenetic analyses are normal.

Pathogenetic implications of internuclear bridging in myelodysplastic syndrome. An Eastern Cooperative Oncology Group/Southwest Oncology Group Cooperative Study

Numerous morphologic features have been described in bone marrow and peripheral blood in myelodysplastic syndrome (MDS). We draw attention to a high incidence of a subtle morphologic feature, internuclear bridging (INB), not previously recognized as a morphologic feature in MDS. The occurrence of INB in MDS suggests an underlying abnormality of mitotic division that could explain the impaired production of hematopoietic cells, the addition and deletion cytogenetic changes, and the stepwise disease progression and cytogenetic progression characteristic of MDS. Lack of awareness that INB occurs in MDS may cause confusion of MDS and congenital dyserythropoietic anemia type I, a congenital process also characterized by INB.

Evolution of multiple cytogenetic clones and leukemic transformation in a case of myelodysplastic syndrome

The cytogenetic follow-up of a case of refractory anemia with excess of blasts (RAEB) that rapidly evolved to acute myeloblastic leukemia (M1-FAB type) is described. Bone marrow analysis at presentation revealed two chromosomally abnormal clones that shared an interstitial deletion of the long arm of chromosome 5 (5q-) and a terminal deletion of the short arm of chromosome 12 (12p-), but that differed from one another in the localization of a very similar segment of chromosome 17 (i.e. 17q11-12qter) on two clearly distinct karyotypic sites: 2q37 and 17q25. Fourteen percent of the metaphases examined bore the 2q+ marker and 38% the 17q+ marker; the remaining cells had a normal karyotype. A second study carried out 4 months later, at onset of the acute phase, revealed that the clone with normal karyotype had almost completely disappeared and that there had been an inversion in the ratio of the two abnormal cell populations. In the final study, made 1 month before death, the cells with t(2;17) had totally effaced the other clone. These findings seem to indicate that, among the karyotypic changes that occurred in an original clone with 5q- and 12p-, only the t(2;17) could have played a crucial role in the final leukemic transformation.

Myelodysplastic syndromes: evolution of overt leukaemia by one or several steps of transformation

The evolution of leukaemia was studied prospectively in 29 patients with myelodysplastic syndrome (MDS) followed for 2-6 years by sequential blast counts, cell kinetics derived from quantitative 14C-autoradiography and karyotype analysis. Overt leukaemia developed in seven patients. Two distinct patterns of leukaemic evolution were identified. The first was characterized by a gradual increase in blast cell count and in the frequency of labelled blasts, and a corresponding reduction in myeloid maturation index indicating increased intracompartmental myeloblast divisions and premature myeloid cell death. A second pattern of leukaemic evolution was marked by a sudden rise in the blast cell population in a previously stable MDS. This rise was attributed both to an increased rate of blast proliferation, and the accumulation of non-proliferating blasts. In an additional patient with smouldering ANLL and multiple karyotype abnormalities, transient clinical remission took place following prednisone and oxymetholone therapy, characterized by a sideroblastic morphology, normal karyotype, and persistence of a highly abnormal myeloid maturation index. The sudden emergence of overt leukaemia in previously stable MDS in some of our patients and the temporary reversal of overt leukaemia into sideroblastic anaemia in one case, lend support to the notion of leukaemic evolution by several steps of transformation. On the other hand, the gradual transition of MDS into overt leukaemia in other patients is compatible with a single step leukaemia transformation, although the possibility of clonal disease prior to the development of MDS cannot be excluded with certainty.

Biology of myelodysplastic syndromes

Myelodysplastic syndromes (MDS) represent a diverse spectrum of disorders ranging from refractory anemia to a preleukemic state. Peripheral cytopenias, cellular marrow, dysplasias and dysfunctions of myeloid and lymphoid cells constitute hematological hallmarks, and are caused by ineffective hemopoiesis. Investigations of cell cultures and cellular functions indicate that the disease originates in a stem cell pluripotent to all myeloid cells and possibly lymphoid cells as well. The disease commonly runs a chronic indolent course, often terminating in acute leukemia or nonleukemic death, notably infections and/or hemorrhage due to cytopenias and cellular dysfunctions. Clonal expansion or clonal evolution appears to be related to the disease progression with a greater degree of malignancy. However, the initial sequence of events causing damage to stem cells is still undefined.

Multiple chromosomally distinct cell populations in myelodysplastic syndromes and their possible significance in the evolution of the disease

Serial chromosome investigations performed in untreated myelodysplastic syndromes (MDS) revealed that: multiple chromosomally unrelated cell populations may emerge during the course of the disease; chromosome changes of the clonal type may disappear or become undetectable, and may or may not reappear during further evolution. The former of these phenomena was found in four cases and was consistently associated with clinical-haematological progression of the disease to a more malignant form, including acute leukaemia. The second was apparently unrelated to clinical and haematological changes in the evolution pattern. These observations are in favour of the hypothesis that MDS evolve as a multistep process in which several events, including the acquisition of sometimes unrelated chromosome changes determine the progression of the disease.

Myelodysplastic syndromes: pathogenesis, functional abnormalities, and clinical implications

The myelodysplastic syndromes represent a preleukaemic state in which a clonal abnormality of haemopoietic stem cell is characterised by a variety of phenotypic manifestations with varying degrees of ineffective haemopoiesis. This state probably develops as a sequence of events in which the earliest stages may be difficult to detect by conventional pathological techniques. The process is characterised by genetic changes leading to abnormal control of cell proliferation and differentiation. Expansion of an abnormal clone may be related to independence from normal growth factors, insensitivity to normal inhibitory factors, suppression of normal clonal growth, or changes in the immunological or nutritional condition of the host. The haematological picture is of peripheral blood cytopenias: a cellular bone marrow, and functional abnormalities of erythroid, myeloid, and megakaryocytic cells. In most cases marrow cells have an abnormal DNA content, often with disturbances of the cell cycle: an abnormal karyotype is common in premalignant clones. Growth abnormalities of erythroid or granulocyte-macrophage progenitors are common in marrow cultures, and lineage specific surface membrane markers indicate aberrations of differentiation. Progression of the disorder may occur through clonal expansion or through clonal evolution with a greater degree of malignancy. Current attempts to influence abnormal growth and differentiation have had only limited success. Clinical recognition of the syndrome depends on an acute awareness of the signs combined with the identification of clonal and functional abnormalities.