Insights into the manifestations, outcomes, and mechanisms of leukemogenesis in Down syndrome.

Children with Down syndrome (DS) show a spectrum of clinical anomalies, including cognitive impairment, cardiac malformations, and craniofacial dysmorphy. Moreover, hematologists have also noted that these children commonly show macrocytosis, abnormal platelet counts, and an increased incidence of transient myeloproliferative disease (TMD), acute megakaryocytic leukemia (AMKL), and acute lymphoid leukemia (ALL). In this review, we summarize the clinical manifestations and characteristics of these leukemias, provide an update on therapeutic strategies and patient outcomes, and discuss the most recent advances in DS-leukemia research. With the increased knowledge of the way in which trisomy 21 affects hematopoiesis and the specific genetic mutations that are found in DS-associated leukemias, we are well on our way toward designing improved strategies for treating both myeloid and lymphoid malignancies in this high-risk population.

Neutrophil elastase and granulocyte colony-stimulating factor receptor mutation analyses and leukemia evolution in severe congenital neutropenia patients belonging to the original Kostmann family in northern Sweden.

BACKGROUND AND OBJECTIVES: Severe congenital neutropenia (SCN) or Kostmann syndrome was originally reported to be an autosomal recessive disease of neutrophil production causing recurrent, life-threatening infections. Mutations in the neutrophil elastase gene (ELA-2) have previously been identified in patients with sporadic or autosomal dominant SCN. DESIGN AND METHODS: We studied 14 individuals (four patients with SCN and ten close relatives) belonging to the original Kostmann family in northern Sweden for mutations in the ELA-2 and the granulocyte colony-stimulating factor (G-CSF) receptor genes. RESULTS: One patient belonging to the original Kostmann family harbored a novel heterozygous ELA-2 mutation (g.2310T-->A;Leu92His) that was not inherited from her parents. The mutation was identified in DNA isolated from both whole blood and skin fibroblasts, suggesting a sporadic de novo mutation. As a young adult this patient sequentially acquired two mutations in the gene for the G-CSF receptor (G-CSFR) and therefore recently received a hematopoietic stem cell transplant, due to the risk of evolution to leukemia. Moreover, another patient developed acute leukemia and was treated with transplantation. No pathogenic ELA-2 or G-CSFR gene mutations were found in this patient or the other two patients, nor in any healthy relative. INTERPRETATION AND CONCLUSIONS: Our data are the first to document leukemia evolution and G-CSFR gene mutations in the original Kostmann kindred. In addition, our findings indicate that ELA-2 mutations are not the primary cause of SCN in the Swedish Kostmann family.

Ocular complications in myelodysplastic syndromes as preleukemic disorders.

PURPOSE: To identify ocular complications in patients with myelodysplastic syndromes (MDS), who have a propensity to progress to acute myeloid leukemia (AML). METHODS: Forty-one patients with MDS were the subjects in this retrospective study, and 21 patients with AML were selected as controls. Reviewing their clinical records, we verified that corneal ulcer, iridocyclitis, vitreous hemorrhage, retinal hemorrhage, and optic neuritis had been evaluated using slit-lamp assessment and opthalmoscopy in all the patients. In this study, the MDS patients were classified into those with refractory anemia (RA) and those with refractory anemia with excess blasts (RAEB). RESULTS: Ocular complications were found in 19 (46.3%) of the 41 patients with MDS, comprising corneal ulcer (two cases), iridocyclitis (five), vitreous hemorrhage (one), retinal hemorrhage (ten), cotton wool spots (one), and optic neuritis (two). (Some patients had more than one ocular complication.) Ocular complications were identified in 12 of the 21 (57.1%) patients with AML. There was no significant difference in frequency of ocular complications between MDS and AML (P = 0.4892). In MDS, retinal hemorrhage was associated with significantly reduced platelet counts (P = 0.0063). The frequency of ocular complications was significantly higher in MDS-RAEB than in MDS-RA (P = 0.0478). Retinal hemorrhage was significantly more frequent in patients with MDS-RAEB than in patients with MDS-RA (P = 0.0433). CONCLUSION: Ocular complications in MDS patients should be carefully examined as prognostic factors for progression to acute leukemia.

Detección de grupos de riesgo en síndromes mielodisplásicos. Un estudio multicéntrico / Detection of risk groups in myelodisplastic syndromes. A multicentric study

Los síndromes mielodisplásicos (SMD) comprenden un grupo heterogéneo de desordenes hematólogicos con riesgo de evolución a leucemia mieloide aguda (LMA). El Grupo Franco-Americano-Británico (FAB) los clasifica en cinco entidades morfológicas y el Sistema Pronóstico Internacional (IPSS) propone cuatro grupos de riesgo basándose en variables clínicas y citogenéticas. El objetivo del trabajo fue evaluar la aplicación del IPSS en población Argentina, analizar el valor pronóstico de sus variables y determinar si dicho sistema permite identificar subgrupos pronósticos de riesgo dentro de los subtipos FAB. Se evaluaron 234 pacientes con SMD de novo (Media de seguimiento: 28 meses), con el fin de determinar sobrevida (SV) y sobrevida libre de LMA (SLL). Se analizaron la clasificación FAB y el IPSS, así como sus variables (número de citopenias, porcentaje de blastos, grupos de riesgo citogenético). Los resultados mostraron diferencias significativas para SV y SLL. La aplicación del IPSS permitió la diferenciación de los cuatro grupos de riesgo y ayudó a identificar subclases pronósticas dentro de los subtipos FAB: 5 , 15 y 19 por ciento de pacientes con peor pronóstico dentro de los subtipos Anemia Refractaria (AR), AR con sideroblastos en anillo (ARSA) y AR con exceso de blastos (AREB), respectivamente. El IPSS no fue informativo para el subtipo AREB en transformación, ni tampoco en pacientes con leucemia mielomonocítica crónica.

Lack of circulating megakaryoblasts in newborn peripheral blood: development and validation of a sensitive flow cytometric detection method.

It is currently thought that approximately 1% of children with Down syndrome will develop a "premalignant" syndrome known as transient myeloproliferative disorder (TMD). Prospective, population-based studies of the incidence of TMD in Down syndrome infants is lacking. Although most cases of TMD resolve by 1 year of age, data suggest that 10% to 20% of Down syndrome patients with TMD develop AML-M7 (megakaryoblastic leukemia). To identify the true incidence of TMD in the Down syndrome population, a sensitive, rapid, and cost-effective method of quantifying circulating megakaryoblasts in large numbers of patients was needed. In this pilot study, the authors tested the hypothesis that there are fewer than 1% megakaryoblasts of nucleated cells circulating in the blood of normosomic infants. Four-antigen flow cytometry was used to establish the percentage of megakaryoblasts present in each of 100 cord blood samples collected blindly from "normosomic" live births. There was a mean percentage of 0.017% megakaryoblasts in 100 cord blood samples from normosomic infants. Flow cytometry proved to be a sensitive, rapid, and reproducible method for the quantification of megakaryoblasts. Less than 1% of circulating nucleated cells in the blood of newborn infants are megakaryoblasts, providing a comparison population for the authors' larger proposed incidence study.

Acute erythroid neoplastic proliferations. A biological study based on 62 patients.

BACKGROUND AND OBJECTIVES: The terms acute erythroleukemia and AML-M6 are defined in the FAB classification as proliferations of dysplastic erythroid elements mixed with blasts of myeloid origin, but pure erythroid leukemias are not included. The recent WHO classification has a category of acute myeloid leukemia not otherwise categorized, which includes acute erythroid leukemia (M6) of two subtypes: M6a-erythroleukemia (erythroid/myeloid) and M6b-pure erythroid leukemia. The aims of this co-operative study were to discover the incidences of these different subtypes, and pay special attention to the morphology of these entities. DESIGN AND METHODS: We reviewed a series of 62 patients with erythroid neoplastic proliferations. Previous medical history, age, sex, peripheral blood and bone marrow cell counts, cytochemical stains, immunophenotype, and cytogenetics were evaluated at presentation. We analyzed the incidence of erythrocyte, leukocyte and platelet abnormalities in the peripheral blood. In bone marrow we analyzed dysplastic features of erythroblasts, granulocytic elements and the megakaryocytic lineage. RESULTS: Fifty-three patients met the criteria of M6a subtype of the WHO classification, and 2 were classified as having pure erythremia (M6b); 7 cases could not be classified according to the WHO criteria. Fifty-five patients presented with de novo acute leukemia, and seven patients had secondary acute leukemia. The most frequent dysplastic features in blood smears were: schistocytes, tear-drop and pincered cells in erythrocytes; hypogranulation and hyposegmentation in leukocytes; gigantism and hypogranulation in platelets. In bone marrow, megaloblastic changes, multinuclearity, karyorrhexis and basophilic stippling in erythroblasts; hypogranulation and gigantism in granulocytic series, and micromegakaryocytes and unconnected nuclei in megakarocytes were the most dysplastic features. A positive PAS reaction and increase of bone marrow iron with ring sideroblasts were common features. Trilineage dysplasia was present in 54% of cases. Dysplastic features in granulocytic elements were absent in 26% of patients and minimal erythroblastic dysplasia was observed in seven patients. A complex karyotype was seen in 27% of patients; chromosomes 5 and 7 were the most frequently involved. INTERPRETATION AND CONCLUSIONS: De novo acute erythroid leukemia was more frequent than secondary cases in our series. The most frequent type of acute erythroid proliferation was the WHO M6a subtype and the least the pure erythroid leukemia. We found a group of seven patients (11%) who could not be classified according to the WHO criteria. Morphologic findings of erythrocytes in peripheral blood, such as schistocytes, tear-drop and pincered cells, were outstanding features. Morphologic aspects remain one of the most important tools for diagnosing these entities.

Elevated plasma level of differentiation inhibitory factor nm23-H1 protein correlates with risk factors for myelodysplastic syndrome.

We measured plasma nm23-H1 level (nm23-H1), a differentiation inhibitory factor, by an enzyme-linked immunosorbent assay (ELISA) in patients with aplastic anemia (AA) and myelodysplastic syndrome (MDS). The nm23-H1 in AA was not significantly elevated when compared to normal subjects (6.66 +/- 1.20 ng/ml vs 5.13 +/- 0.81 ng/ml; P = 0.274). In contrast, MDS patients had significantly high levels of nm23-H1 compared not only to normal subjects (11.16 +/- 1.42 vs 5.13 +/- 0.81 ng/ml; P = 0.0004) but also to those of the AA group (11.16 +/- 1.42 ng/ml vs 6.66 +/- 1.20 ng/ml; P = 0.018). In the MDS group of patients, no significant difference was observed in the nm23-H1 levels between patients with refractory anemia (RA) and RA with excess blasts (RAEB)/RAEB in transformation (10.71 +/- 1.61 ng/ml vs 9.24 +/- 2.66 ng/ml; P = 0.672). Of the patients with RA, patients with low risk according to the International Prognostic Scoring System (IPSS) had significantly low levels of nm23-H1 compared to those of IPSS INT-1 level cases (6.40 +/- 1.36 ng/ml vs 13.05 +/- 2.50 ng/ml; P = 0.0028), suggesting that nm23-H1 may be useful as a prognostic marker for MDS, especially in low risk patients.

Detection of risk groups in myelodysplastic syndromes. A multicenter study.

BACKGROUND AND OBJECTIVES: Myelodysplastic syndromes (MDS) comprise a group of heterogeneous hematologic disorders with risk of leukemic evolution (LE). The French-American-British (FAB) co-operative group classifies them into five morphologic entities and the International Prognostic Scoring System (IPSS) proposes four groups of risk on the basis of clinical and cytogenetic variables. The aim of this study was to evaluate the application of the IPSS in our Argentine population, to test the prognostic value of its variables and to determine whether this score helps to associate prognostic subgroups of risk into FAB subtypes. DESIGN AND METHODS: Two hundred and thirty-four patients with primary MDS and a median follow-up of 28 months were evaluated using univariate analyses to determine median survival (SV) and the time to LE. The variables analyzed were FAB classification, IPSS, percentage of myeloblasts, cytogenetic groups of risk and number of cytopenias. RESULTS: Univariate analyses showed that all variables analyzed were predictive for SV and for LE in our MDS population. Application of the IPSS allowed discrimination into the 4 groups of risk and helped to identify prognostic subclasses among the FAB classification, associating 5%, 15% and 19% of cases with worse prognosis within the FAB classification of refractory anemia (RA), RA with ringed sideroblasts and RA with excess of blasts (RAEB), respectively. The IPSS was not informative for RAEB in transformation cases and would not be applied to patients with chronic myelomonocytic leukemia. INTERPRETATION AND CONCLUSIONS: This score could be applied to our MDS population, showing no geographic differences. Stratification of FAB patients according to IPSS would be helpful to develop risk-adapted therapeutic strategies.

Leukemogenic risk of hydroxyurea therapy in polycythemia vera, essential thrombocythemia, and myeloid metaplasia with myelofibrosis.

In polycythemia vera (PV), treatment with chlorambucil and radioactive phosphorus (p32) increases the risk of leukemic transformation from 1% to 13-14%. This risk has been estimated to be 1-5.9% with hydroxyurea (HU) therapy. When compared with historical controls, the risk with use of HU does not appear to be statistically significant. The leukemogenic risk of HU therapy in essential thrombocytosis (ET) and in myelofibrosis with myeloid metaplasia (MMM) is unknown. HU remains the main myelotoxic agent in the treatment of PV, ET, and MMM. We studied 64 patients with these three disorders, seen at our institution during 1993-1995. The patients were studied for their clinical characteristics at diagnosis, therapies received, and development of myelodysplasia or acute leukemia (MDS/AL). Forty-two had PV, 15 ET, and 6 MMM, and 1 had an unclassified myeloproliferative disorder. Of the 42 patients with PV, 18 were treated with phlebotomy alone, 16 with HU alone, 2 with p32, 2 with multiple myelotoxic agents, and 2 with interferon-alpha (IFN-alpha). Two patients from the phlebotomy-treated group, one from the HU-treated group, and 1 from the multiple myelotoxic agent-treated group developed MDS/AL. In the larger group, 11 received no treatment or aspirin alone, 18 were treated with phlebotomy alone, 25 with HU, 5 with multiple myelotoxic agents, 2 with p32, 2 with IFN-alpha, and 1 with melphalan. Study of the entire group of 64 patients showed that only one additional patient (total of 5 out of 64) developed MDS/AL. This patient had been treated with HU alone. Statistical analysis did not show any association between clinical characteristics at diagnosis, or HU therapy, and development of MDS/AL (P=0.5). Thus, our data provide no evidence suggestive of increased risk of transformation to MDS/AL with HU therapy in PV, ET, and MMM. Larger, prospective studies are needed to study this issue further.

Epidemiology of acute promyelocytic leukemia.

BACKGROUND: The estimated incidence of acute promyelocytic leukemia (APL) is approximately 6 cases per 10 million people per year with no apparent differences between sexes. The age of APL cases is younger than that of other acute myeloid leukemias (AML). Spatial and temporal clusters of APL have been reported. These observations suggest a possible selective role for environmental and/or occupational factors in APL development. METHODS: A multicenter case-control study was carried out on risk factors for acute leukemias and preleukemias. In this report data related to APL are selectively analyzed from the larger study to identify specific risk factors. RESULTS: The case-control study on 38 cases of APL showed a strong association with shoemaking (odds ration 6.3, 95% confidence interval 1.3-31.1). A moderate leukemogenic effect from living in houses built with tuff, a polous building material containing gamma-emitting radionuclides and having a high radon concentration, and from using hair dyes was also suggested. CONCLUSIONS: These data, together with the reported spatial and temporal clustering of APL, support the hypothesis of specific environmental and/or occupational risk factors for APL among other AML subtypes and indicate the need for additional ad hoc multicenter studies.

Long-term outcome of postremission chemotherapy for adults with acute myeloid leukemia using different dose-intensities.

The long-term results of postremission chemotherapy for 122 consecutive, unselected adults (15-65 years) with acute myeloid leukemia (AML) were assessed in two sequential prospective studies involving an identical 3/7-type induction regimen, and in those achieving remission, another course for early consolidation using 1 day of daunorubicin instead of three. Forty-one patients reaching C.R. during the first study period, were treated with an intensive ablative maintenance ("IM") program for a period of 9 months. They were randomized to either 6 cycles of induction-type regimen or to 6 cycles of an alternating-type regimen consisting of high-dose (HD)-Ara C/AMSA or 5-azacytidine/AMSA every 6 weeks. There was no difference in disease-free survival (DFS) or survival. Results are compared with 27 patients reaching C.R. on the subsequent protocol where IM was replaced by intensive, short-term consolidation ("IC") using 1 cycle of intermediate-dose Ara C plus AMSA and 1 cycle of HD-AraC/AMSA. Fifteen patients received both courses of IC as scheduled, 12 refused the second cycle. There was no significant difference in DFS or survival. Seventeen out of the 122 patients refused either IM or IC following early consolidation ("refusals"). They received no further treatment and served as control. Fourteen percent of all patients underwent autologous or allogeneic bone marrow transplantation (BMT) at different stages of their disease, equally distributed amongst the IM and IC-group. Median DFS was 3.3 months in the refusal group, 12.4 months in the IM-group, and 18.4 months in the IC-group when censored for BMT (p = 0.01) with 6%, 12%, and 40% in C.C.R. at 50 months. Accordingly, median survival was 5.4, 20 and 47 months (p = 0.001) with 6%, 15%, and 45% of patients alive at 5 years. There was a definite trend (p = 0.14) for a higher proportion of long-term survivors in the IM-group when BMT was performed (not censored), while long-term survival was identical in the IC-group whether BMT was considered for analyses (not censored) or not (censored). Median follow-up for both studies is 5.6 years, the longest, 10 years. In conclusion, progressive increments in the intensity of postremission therapy yields in a graded, significant improvement of remission duration and survival.

Benefit of high-dose cytarabine-based consolidation chemotherapy for adults with acute myelogenous leukemia.

Despite consolidation and/or maintenance chemotherapy most patients with newly diagnosed acute myelogenous leukemia relapse such that only 20-30% survive free of recurrence at five years. To evaluate the long-term effects of dose-intensive consolidation, we analysed 123 consecutive patients, age 16 to 84 (median 48 years), who received high-dose cytarabine-based consolidation chemotherapy. After a median follow-up of 88 months (range 26 to 126 months), 38 patients remain alive, with 26 in continued remission from 45 to 126+ months. Median remission duration for all eligible patients is 14 months (range 1.3 to 126 months) and actuarial leukemia-free survival at five years is 24 +/- 8%. Median survival from remission is 24 months (range 1.3 to 126 months) and actuarial survival from remission is 31 +/- 9%. Eighty-two patients (67%) have relapsed with an actuarial risk of relapse of 71 +/- 9% at five years. Adverse prognostic factors were age over 45 and male gender. When compared to historical controls (P = 0.02), dose-intensive consolidation produced improved leukemia-free survival for patients age < 45, but compliance and enhanced toxicity in the older age groups may limit further dose intensification.

Hair dye use and other risk factors for leukemia and pre-leukemia: a case-control study. Italian Leukemia Study Group.

A case-control study was carried out to examine the relation of three subtypes of leukemia cells and refractory anemia with excess of blasts to selected behavioral and environmental factors. Cases aged 15 years or older were recruited in three hospitals located in Rome, Bologna, and Pavia, respectively. Outpatients who were either normal or had nonneoplastic hematologic disorders and were seen in the same hospitals as the cases were enrolled as controls. Two hundred fifty-two patients with acute myeloid leukemia, 100 with acute lymphocytic leukemia, 111 with refractory anemia with excess of blasts, 156 with chronic myeloid leukemia, and 1,161 controls were included in the study. Refractory anemia with excess of blasts and chronic myeloid leukemia were included because they are regarded as forms of pre-leukemia. Odds ratio estimates were generally imprecise, but associations were suggested between specific case subtypes and exposure to dark hair dye, selected occupations (shoemaker, painter, electrician, child care), residence in houses built with tuff, and smoking. Although the exploratory nature of the study and its limited statistical power preclude firm conclusions, its results are consistent with those of previous studies, and are in general biologically plausible.

Clinical course of human T-lymphotropic virus type I carriers with molecularly detectable monoclonal proliferation of T lymphocytes: defining a low- and high-risk population.

To characterize the prodromal phase of adult T-cell leukemia (ATL), a prospective follow-up study was conducted on 50 carriers in a putative pre-ATL state. This state was defined by the presence of molecularly-detectable monoclonal proliferation of human T-lymphotropic virus type I (HTLV-I)-infected T lymphocytes, and the absence of clinical symptoms of leukemia. The median observation time was 50 months. The pre-ATL subjects were divided into two groups according to initial white blood cell (WBC) counts: group A, those with a normal WBC count (9,000/microL) (n = 30), and group B, those with an increased WBC count (9,000 to 15,000) (n = 20). Comparisons were made between the two groups and with a group of 25 patients with chronic ATL (group C) who had WBC counts of more than 15,000. Significant differences in survival rate were found between groups A and B (10-year survival 65.7%) and group C (32.8%) (P < .01), and between group A (10-year survival 90.0%) and group B (52.1%) (P < .05). The incidence of transformation to overt ATL was 10% (3 of 30) in group A and 50% (10 of 20) in group B (P < .01). In six transformed cases (one in A and five in B) we found exactly the same integration sites in pre-ATL and overt ATL phases, confirming the multistep leukemogenesis hypothesized for this disease. However, the pre-ATL subjects could be divided into two distinct prognostic groups based on the initial WBC count; those with good and those with poor prognosis. Although the 10% transformation rate (2.5% annually) in group A seemed to be extremely high compared with that in the general population of HTLV-I carriers (around 0.06% to 0.4% annually), the majority of group A subjects and some in group B showed stable clinical courses without transformation. Further, development of ATL was not observed in four group A subjects with HTLV-I-associated myelopathy (HAM), which is rarely associated with ATL. We propose to call this group of rather benign HTLV-I carriers "HTLV-I carriers with monoclonal proliferation of T lymphocytes (HCMPT)." Thus far we have been unable to identify reliable parameters other than WBC counts that prospectively distinguish HCMPT from the true pre-ATL state, in which there is a high probability of developing ATL. Further clinical and biologic approaches should elucidate the natural history of the HTLV-I carrier state and early events in ATL leukemogenesis.

Poor prognosis acute myelogenous leukemia.

Poor prognosis AML consists of 3 clinically definable groups of patients whose response to therapy is substantially worse than that of standard prognosis patients. The response rate is lowest for those patients who have more than a single risk factor and for the patients who have low platelet and serum albumin levels at diagnosis. The treatment associated mortality of the latter patients is quite high. Even if one avoids the high mortality rate by carefully selecting patients the likelihood that drug resistant disease is present is very high. Since the basis for resistance is multifactorial, a variety of strategies will have to be explored as means to improve treatment outcome. At the present time, the greatest chance for long term survival is found in relatively young patients whose AML is induced into complete remission and who then receive a matched allogeneic bone marrow transplant.

Leukemia in Down syndrome: a review.

The incidence of leukemia is higher in children with Down syndrome (DS) than in normals. In approximately 50% of cases the type of leukemia is acute megakaryoblastic leukemia (AMKL) and it occurs during the first 4 years of life. The leukemic cell also has features of erythroid progenitors and therefore appears to be a precursor cell with biphenotypic properties. In addition, newborns with DS frequently develop transient leukemia (TL), which is characterized by the presence of megakaryoblasts in the blood which disappear during the first 1-3 months of life. The incidence of this disorder is unknown although preliminary studies suggest that megakaryoblasts may be found frequently in the blood of DS newborns. TL does not occur in normal newborn infants. Although TL disappears spontaneously, many of these children will develop AMKL at 1-4 years of age. Recent surveys suggest that 20-30% of newborns with TL will develop AMKL. Preliminary evidence suggests that TL is a clonal proliferation, can be fatal, and may occur in a specific subgroup of DS children. The observations in this report are drawn from our own experience, reports in the literature, and data accumulated in the Canadian Down Syndrome Leukemia Registry.

[Myelodysplastic syndromes. Hematologic phenotypes, cytogenetic expression and clinical course in 133 cases (1979-1989)]. / Síndromes mielodisplásticos. Fenotipos hematológicos, expresión citogenética y patrones evolutivos de 133 casos (1979-1989).

One hundred and thirty-three cases of myelodysplastic syndromes studied during the last ten years were revised. Of them, 79 were males and 54 females, and their ages ranged between 15 and 91 years (median, 69 years). Five patients (3.7%) had secondary myelodysplasias. The haematological phenotype (FAB) of the cases was: RA, 41.3%; SRA, 24%; RAEB, 18%; RAEBT, 3.7%; CMML, 8.3%. Leucopenia/thrombocytopenia without initial anaemia was present in 4.5% of the cases. Abnormal karyotype was found in 54 patients (40.6%), MIKA in 41 cases and MAKA in 13 cases. The cytogenetic anomalies most commonly found were +8, 5q-, -7, 11q- and 13q-. Cytogenetic abnormalities were commonest amongst the RAEB (50%), and least frequent in CMML (18.2%). Thirty-one patients evolved into acute leukaemia (29 ANLL and 2 ALL). Such blastic changes were more frequent in RAEB (62.5%) and rarest in SRA (9.4%), and they appeared mostly in patients with complex karyotype (MAKA) (53.8%) as compared with those who had normal karyotype (17.7%). Short-lasting complete remission was achieved by 40% of the patients treated with conventional chemotherapy. The survival of the group as a whole (median 30 months) varied in accordance with the haematological phenotype: SRA, 81 months; RA, 65 months; CMML, 13 months; RAEB +/- T, 8 months. The finding of a MAKA karyotype significantly shortened the survival (4 months) with regard to MIKA (44 months) or normal karyotype (39 months). The following median survivals were attained after patients' staging (Bournemouth's criteria): stage A, 84 months; stage B, 22 months, and stage C, 5 months.(ABSTRACT TRUNCATED AT 250 WORDS)