The preleukemic syndrome: clinical and laboratory features, natural course, and management

Enhanced growth of myelodysplastic colonies in hypoxic conditions

OBJECTIVE

To determine the response of bone marrow progenitor cells from patients with myelodysplastic syndromes (MDS) to culture in physiologic oxygen tension.

METHODS

Methylcellulose progenitor assays using both unfractionated bone marrow mononuclear cells (MNCs) and purified CD34(+) progenitors were performed in atmospheric oxygen (18.6% O(2)) or one of two levels of hypoxia (1% and 3% O(2)). Assays were performed using normal donor marrow, MDS patient marrow, acute myelogenous leukemia marrow or peripheral blood blasts, chronic phase chronic myelogenous leukemia (CML) marrow MNCs, and blast crisis CML peripheral blood.

RESULTS

The majority of MDS samples showed decreased colony-forming units (CFU) in 18.6% O(2) compared to normal controls, as expected. However, in either 1% or 3% O(2), 9 of 13 MDS samples demonstrated augmentation of CFUs beyond that observed in normal controls, with 6 of 13 demonstrating a greater than ninefold augmentation. This effect is cell autonomous, as it persisted after purification of CD34(+) progenitor cells. Additionally, the augmented response to physiologic oxygen tension is specific to MDS, as it was not observed in either acute or chronic myelogenous leukemia samples.

CONCLUSION

These results suggest that the reported decrease in MDS CFUs reflects greater sensitivity of MDS progenitors or their progeny to the nonphysiologic oxygen tensions routinely used in vitro, rather than a true decrease in progenitor frequency. Importantly, these experiments for the first time describe an experimental system that can be used to study the growth of primary cells from patients with MDS.

Myelodysplastic syndrome with erythroid hypoplasia

The incidence of myelodysplastic syndrome (MDS) with erythroid hypoplasia/aplasia is probably underestimated because in most patients it is mistaken for acquired pure red blood cell aplasia. This report describes three children who fulfilled the criteria for MDS with erythroid hypoplasia/aplasia. All these patients had transfusion dependent anaemia, reticulocytopenia, erythroid hypoplasia/aplasia, severe dysgranulopoiesis, and dysmegakaryopoiesis.

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.

Haematological features of primary myelodysplastic syndromes (PMDS) at initial presentation: a study of 118 cases

The haematological features of 118 cases of primary myelodysplastic syndromes (PMDS) were reviewed to see how these could be related and classified according to the recent FAB proposals. A majority of the cases were elderly who presented with a macrocytic or normocytic anaemia and reticulocytopenia. Cases of acquired idiopathic sideroblastic anaemia (AISA) usually had normal leucocyte and platelet counts, erythroid hyperplasia, marked dyserythropoiesis and more than 20% ringed sideroblasts. Cases of refractory anaemia with excess of blasts (RAEB) had frequent neutropenia and thrombopenia usually with prominent dysgranulopoiesis and dysthrombopoiesis. Refractory anaemia or refractory cytopenia appeared morphologically to be a heterogeneous group. Leukaemic transformation did not occur in any of these 16 cases of AISA whereas six of the 34 cases of RAEB transformed into acute leukaemia. It appears that the cases of PMDS present with well defined haematological features which permit recognition of different groups; these latter groups appear to be morphologically and prognostically distinct.

On the pathogenesis of preleukemic myelodysplastic syndromes: development of a dysplastic hemopoietic proliferation in the rat after a single pulse dose of dimethylbenz(a)anthracene (DMBA)

After a single pulse dose of DMBA, rats develop bone-marrow hypoplasia, which is almost compensated for by regeneration after 16 weeks. Subsequently, dysplastic signs of hemopoiesis appear in all experimental animals as massive extrusion of normoblasts into the peripheral blood, red-cell aniso- and poikilocytosis, nuclear deformities, atypical mitoses, and PAS-positivity, as well as megaloblastoid maturation dissociation of erythroblasts and nuclear and granulation anomalies of neutrophilic granulocytes and monocytes, comparable to human "pseudo-Pelger cells" and "paraneutrophils". At the time of death (112-497 days after DMBA pulse) experimental animals showed hyperplastic bone marrow with increased granulopoietic/erythropoietic ratios and an augmented, mainly erythropoietic, hemopoiesis in the spleen, with splenomegaly in six rats. Splenic hemopoiesis is accompanied by white pulp atrophia. The cause of death was septicopyemia in three rats, anemia in three, and bleeding in one rat. None of the animals developed a leukemic blast phase. Myelodysplastic changes in this experiment are the same as have been shown to precede leukemia in rats treated with five DMBA pulses (Fohlmeister et al. 1981). Possible relations of myelodysplasia and leukemia are discussed.