Increased chromosome damage in systemic sclerosis skin fibroblasts.

OBJECTIVE: To evaluate chromosome damage, by means of micronucleus frequency, in dermal fibroblasts from affected and non-affected skin from systemic sclerosis (SSc) patients and from controls. METHODS: Primary fibroblast cultures were obtained by biopsy from affected and non-affected skin from SSc patients. Control fibroblasts were derived from skin remnants from plastic surgery in healthy adults. The number of micronuclei-bearing cells per 1000 binucleated cells (MN+ cells/1000 BN) was determined in cultures with and without clastogenic stimulus (bleomycin 3 µg/mL). RESULTS: Primary cultures from 10 SSc patients (affected and non-affected skin) and nine controls were analysed by two blinded examiners. In the absence of bleomycin, the frequency of MN+ cells was higher in cultures from affected (14.01 ± 11.96 MN+ cells/1000 BN; p = 0.004) and non-affected (15.41 ± 13.58 MN cells/1000 BN; p = 0.005) skin from SSc patients as compared to fibroblasts from healthy controls (4.74 ± 3.30 MN cells/1000 BN). In bleomycin-treated cultures, the frequency of MN cells was higher in SSc affected (38.03 ± 26.14 MN cells/1000 BN; p = 0.041) and non-affected skin (38.47 ± 17.88 MN cells/1000 BN; p = 0.034) as compared to healthy control fibroblasts (20.54 ± 13.09 MN cells/1000 BN). There was no difference in the frequency of MN cells in cultures from affected and non-affected skin of SSc patients. CONCLUSIONS: This is the first demonstration that dermal fibroblasts from SSc patients present an increased frequency of spontaneous and clastogen-induced micronuclei. Increased clastogenesis seems to be a widespread phenomenon in SSc because fibroblasts from clinically affected and non-affected skin presented the equivalent increased micronuclei counts.

High risk for unbalanced segregation of some reciprocal translocations: a large pedigree containing distal 4q trisomy from t(4;7)(q28;p22).

We report on a familial t(4;7)(q28;p22) with 2:2 adjacent-1 unbalanced segregation producing duplication of 4q28-->qter in multiple offspring. Within the large four-generation pedigree, a carrier had a reproductive outcome that was approximately equal for 1) the balanced translocation, 2) normal chromosomes, and 3) viable 4q trisomy or pregnancy loss. The three individuals with chromosomal confirmation of trisomy 4q28-->qter (comprising approximately 1.8% of the haploid autosomal length) had similar mental and developmental retardation, hypotonia, restricted speech, seizures, and facial anomalies but no cardiac, renal, or skeletal anomalies. It is suggested that these latter severe malformations, associated with the classic 4q2 to 3 group of anomalies, were from an imbalance outside 4q28-->qter and were not necessarily related to the relatively large size of the trisomic segment. Multiple different chromosomes are reported to be rearranged with 4q in the production of distal 4q trisomy. The incidence of 4q rearrangement remains unexplained, but once it is present in a family, viability of a large trisomy in 4q seems to explain the number of affected individuals reported.

Karyotype of cryopreserved bone marrow cells.

The analysis of chromosomal abnormalities is important for the study of hematological neoplastic disorders since it facilitates classification of the disease. The ability to perform chromosome analysis of cryopreserved malignant marrow or peripheral blast cells is important for retrospective studies. In the present study, we compared the karyotype of fresh bone marrow cells (20 metaphases) to that of cells stored with a simplified cryopreservation method, evaluated the effect of the use of granulocyte-macrophage colony-stimulating factor (GM-CSF) as an in vitro mitotic index stimulator, and compared the cell viability and chromosome morphology of fresh and cryopreserved cells whenever possible (sufficient metaphases for analysis). Twenty-five bone marrow samples from 24 patients with hematological disorders such as acute myeloid leukemia, acute lymphoblastic leukemia, myelodysplastic syndrome, chronic myeloid leukemia, megaloblastic anemia and lymphoma (8, 3, 3, 8, 1, and 1 patients, respectively) were selected at diagnosis, at relapse or during routine follow-up and one sample was obtained from a bone marrow donor after informed consent. Average cell viability before and after freezing was 98.8 and 78.5%, respectively (P < 0.05). Cytogenetic analysis was successful in 76% of fresh cell cultures, as opposed to 52% of cryopreserved samples (P < 0.05). GM-CSF had no proliferative effect before or after freezing. The morphological aspects of the chromosomes in fresh and cryopreserved cells were subjectively the same. The present study shows that cytogenetic analysis of cryopreserved bone marrow cells can be a reliable alternative when fresh cell analysis cannot be done, notwithstanding the reduced viability and lower percent of successful analysis that are associated with freezing.

Acute promyelocytic leukemia: the study of t(15;17) translocation by fluorescent in situ hybridization, reverse transcriptase-polymerase chain reaction and cytogenetic techniques.

Acute promyelocytic leukemia (AML M3) is a well-defined subtype of leukemia with specific and peculiar characteristics. Immediate identification of t(15;17) or the PML/RARA gene rearrangement is fundamental for treatment. The objective of the present study was to compare fluorescent in situ hybridization (FISH), reverse transcriptase-polymerase chain reaction (RT-PCR) and karyotyping in 18 samples (12 at diagnosis and 6 after treatment) from 13 AML M3 patients. Bone marrow samples were submitted to karyotype G-banding, FISH and RT-PCR. At diagnosis, cytogenetics was successful in 10 of 12 samples, 8 with t(15;17) and 2 without. FISH was positive in 11/12 cases (one had no cells for analysis) and positivity varied from 25 to 93% (mean: 56%). RT-PCR was done in 6/12 cases and all were positive. Four of 8 patients with t(15;17) presented positive RT-PCR as well as 2 without metaphases. The lack of RT-PCR results in the other samples was due to poor quality RNA. When the three tests were compared at diagnosis, karyotyping presented the translocation in 80% of the tested samples while FISH and RT-PCR showed the PML/RARA rearrangement in 100% of them. Of 6 samples evaluated after treatment, 3 showed a normal karyotype, 1 persistence of an abnormal clone and 2 no metaphases. FISH was negative in 4 samples studied and 2 had no material for analysis. RT-PCR was positive in 4 (2 of which showed negative FISH, indicating residual disease) and negative in 2. When the three tests were compared after treatment, they showed concordance in 2 of 6 samples or, when there were not enough cells for all tests, concordance between karyotype and RT-PCR in one. At remission, RT-PCR was the most sensitive test in detecting residual disease, as expected (positive in 4/6 samples). An incidence of about 40% of 5' breaks and 60% of 3' breaks, i.e., bcr3 and bcr1/bcr2, respectively, was observed.

Prognostic significance of BCR-ABL rearrangement in chronic myeloid leukemia.

Chronic myeloid leukemia (CML) is a myeloproliferative disorder characterized by the presence of a reciprocal translocation between chromosomes 9 and 22 in at least 95% of cases. At the molecular level, this translocation results in the activation of the ABL oncogene of chromosome 9, which becomes contiguous with the 5' end of the BCR gene on chromosome 22. The breakpoint usually occurs between exons 2 and 3 (b2-a2 rearrangement), or 3 and 4 (b3-12 rearrangement) of the major breakpoint cluster region (M-BCR) of the BCR gene. The aim of the present study was to characterize the type of BCR-ABL transcript in 32 patients with CML using the reverse transcriptase-polymerase chain reaction (RT-PCR) and to determine if this type of rearrangement is related to the survival of the patients. Our results confirmed that RT-PCR is more sensitive than cytogenetic analysis for identifying the Philadelphia (Ph1) chromosome (96.9% vs 79.3%). The frequencies of b2-a2 and b3-a2 rearrangements were 28.1% and 65.7%, respectively. The survival of patients presenting the b2-a2 or the b3-a2 rearrangement was not significantly different (P = 0.27750). The data suggest that the type of transcript has no prognostic value for CML patients.

Acute myeloid leukemia in elderly patients: experience of a single center.

Acute myeloid leukemia (AML) is a disease predominantly of older adults. Treatment of AML in the elderly is complicated not only by comorbidities but also by the high prevalence of poor prognosis markers. Thirty-one consecutive unselected patients with AML older than 60 years (representing 33% of all AML cases diagnosed at our institution during the same period) were followed over a period of 5 years (1997-2002). A high incidence of AML with multilineage dysplasia (45%) and no favorable cytogenetic abnormalities but 62% intermediate and 38% unfavorable karyotypes were found. Sixteen patients (52%) were selected for induction of intensive cytotoxic treatment and complete remission was achieved only by some of these intensively treated patients (7 of 16). Of these, 3 remained alive without disease (median: 11 months), 1 patient died shortly after complete remission, and 3 patients relapsed and died from refractory disease. Only 1 patient that was refractory to intensive cytotoxic treatment remained alive with disease under supportive care. Fifteen patients (48%) were managed with palliative/supportive care: 7 received palliative treatment and supportive care, 8 received supportive care only, and 4 patients remained alive with disease under supportive care (median: 9 months). Mortality rate was 74% and overall survival at two years was 12%. To the best of our knowledge, there is no previous report regarding elderly patients with AML in Brazilian subsets. The present data are similar to previously reported studies showing that elderly AML patients are not only older but also biologically distinct from younger AML patients, particularly in terms of the high incidence of poor prognostic karyotypes and resistance to therapy.

Chronic myeloid leukemia (CML): prognostic factors and survival analysis.

The prognostic value of different factors upon diagnosis of CML was analysed in 45 Philadelphia (Ph1)-positive patients. The median survival was 48 months. Univariate analysis showed 5 poor prognostic factors (male sex, under 45 years-old, bone marrow blasts greater than or equal to 10 percent, blood basophils greater than or equal to 6 percent and blood eosinophils greater than or equal to 6 percent) which provided for the development of a clinical staging system: Stage I with none or one factor and a two-year survival rate of 100 percent; Stage II with two or three factors and two-year survival of 72.2 percent; and Stage III with four or five factors and two-year survival of 0 percent (p = 0.00016). Multivariate survival analysis showed that combination of blood basophilia and bone marrow blasts had the strongest predictive relationship to survival time. We conclude that a combination of pretreatment factors identifies different risk subcategories in CML patients and is helpful in assessing the overall prognosis and the treatment approach.

A t(9;11) translocation in childhood acute mixed leukemia.

We present the case of a child with acute lymphoid leukemia (ALL) who was morphologically classified as FAB L1 (PAS and peroxidase were negative). Remission was achieved with an ALL-type protocol (GBTLI). Five months after the discontinuation of therapy, the patient presented mixed leukemia (CD10, CD19, CD13 and CD33 were positive) with t (9;11) (p21;q23) translocation. Unfortunately, as cytogenetic and immunophenotype studies were not performed at diagnosis, two possibilities could be considered for the relapse; secondary mixed leukemia with clonal chromosome changes, or mixed leukemia from the beginning.

[Cytogenetic abnormalities as prognostic factors in acute myeloid leukemia]. / Alterações citogenéticas como fatores prognósticos em leucemias mielóides agudas.

UNLABELLED: The study of chromosomal abnormalities in AML has become very important in the diagnosis and in the characterization of subtypes since they are related to defined clinical, morphological and immunological features as well as treatment outcome and survival. PURPOSE: To evaluate the relative importance of cytogenetic abnormalities may have in AML patients. METHODS: 13 AML patients were studied during diagnosis. Cytogenetic study was performed on bone marrow aspirate material. RESULTS: M1 and M2 FAB subtypes were the most frequent (61.6%). The patients' median age was 38 years. Cytogenetic analysis showed abnormal karyotype in 61.5% of the cases and 15.3% of whom had abnormalities considered as good prognosis [t(15;17) and t(8;21)]. At the evaluation day there were 3 patients alive, two in continuous complete remission and 1 in a second remission. The median total survival time was 7 months. Patients were divided into two groups: a "good prognosis" one, that joined 5 patients with normal karyotype and 2 with the translocations t(15;17) and t(8;21) and another, the "bad prognosis" one, with 8 patients with unfavorable chromosomal abnormalities. The good prognosis group had a median survival time of 9 months versus 6.2 months in the other, but this was not statistically significant (p = 0.18), probably owing to the small number of cases in the groups. But when one observes the cases separately see that patients with translocations (8;21) and (15;17), known as good prognosis, had longer survivals. CONCLUSION: The different survival time between the two groups showed the importance of cytogenetic study to distinguish the patient who will have favorable evolution.

Cytogenetic studies of Brazilian pediatric myelodysplastic syndrome cases: challenges and difficulties in a large and emerging country.

Myelodysplastic syndromes (MDS) and juvenile myelomonocytic leukemia (JMML) are rare hematopoietic stem cell diseases affecting children. Cytogenetics plays an important role in the diagnosis of these diseases. We report here the experience of the Cytogenetic Subcommittee of the Brazilian Cooperative Group on Pediatric Myelodysplastic Syndromes (BCG-MDS-PED). We analyzed 168 cytogenetic studies performed in 23 different cytogenetic centers; 84 of these studies were performed in patients with confirmed MDS (primary MDS, secondary MDS, JMML, and acute myeloid leukemia/MDS+Down syndrome). Clonal abnormalities were found in 36.9% of the MDS cases and cytogenetic studies were important for the detection of constitutional diseases and for differential diagnosis with other myeloid neoplasms. These data show the importance of the Cooperative Group for continuing education in order to avoid a late or wrong diagnosis.

Application of five prognostic survival scores to primary myelofibrosis in 62 Brazilian patients.

Primary myelofibrosis (PM) is a Philadelphia-negative clonal hematopoietic stem cell disorder characterized by intense reactive changes of bone marrow stroma with collagen fibrosis, osteosclerosis and angiogenesis. PM usually affects elderly people, and approximately half of the patients present JAK2V617F mutation. PM clinical course varies from 1 to 30 years, evolving from asymptomatic into progressive bone marrow failure, symptomatic splenomegaly or acute leukemia in 10-20 % of cases. PM risk stratification is based on parameters predicting survival, and several attempts have been made to identify clinical and laboratory features that could predict PM patient survival. This study applied five prognostic scores: Dupriez, Cervantes, Mayo, IPSS and DIPSS-Plus in 62 Brazilians patients from three centers, and compared their relevance and clinical usefulness considering the scores' parameters, fibrosis, JAK2V617F mutation, splenomegaly, hepatomegaly and treatment. According to the Cervantes, Dupriez and Mayo scores, most patients were stratified into low-risk group. However, when IPSS and DIPSS-Plus were applied, most patients were classified into an intermediate range, being low risk in only 11 and 13 % of patients, respectively. Overall survival at 4 years was 84 %. The Cervantes score was the only one that remained significantly associated with survival in a multivariate analysis. In conclusion, the Cervantes score remains important to the prognostication of PM.

Invasive fungal diseases in haematopoietic cell transplant recipients and in patients with acute myeloid leukaemia or myelodysplasia in Brazil.

Invasive fungal disease (IFD) shows distinct regional incidence patterns and epidemiological features depending on the geographic region. We conducted a prospective survey in eight centres in Brazil from May 2007 to July 2009. All haematopoietic cell transplant (HCT) recipients and patients with acute myeloid leukaemia (AML) or myelodysplasia (MDS) were followed from admission until 1 year (HCT) or end of consolidation therapy (AML/MDS). The 12-month cumulative incidence (CI) of proven or probable IFD was calculated, and curves were compared using the Grey test. Among 237 AML/MDS patients and 700 HCT recipients (378 allogeneic, 322 autologous), the 1-year CI of IFD in AML/MDS, allogeneic HCT and autologous HCT was 18.7%, 11.3% and 1.9% (p <0.001), respectively. Fusariosis (23 episodes), aspergillosis (20 episodes) and candidiasis (11 episodes) were the most frequent IFD. The 1-year CI of aspergillosis and fusariosis in AML/MDS, allogeneic HCT and autologous HCT were 13.4%, 2.3% and 0% (p <0.001), and 5.2%, 3.8% and 0.6% (p 0.01), respectively. The 6-week probability of survival was 53%, and was lower in cases of fusariosis (41%). We observed a high burden of IFD and a high incidence and mortality for fusariosis in this first multicentre epidemiological study of IFD in haematological patients in Brazil.

Systemic vasculitis in myelodysplastic syndromes.

The development of immunological abnormalities in various neoplasms is a rather common phenomenon. The prevalence of life-threatening systemic vasculitis in malignancy, however, is much lower. Nonetheless we found an unexpected frequency of several autoimmune manifestations, including systemic vasculitis, in certain myelodysplastic syndromes. We illustrate this finding with the case of a 43-year-old man with signs of polyarteritis nodosa-like systemic vasculitis during progression of chronic myelomonocytic leukaemia. Subsequently, we review the literature on the combination of myelodysplastic syndromes and systemic vasculitis and discuss the prognostic consequences, considerations for treatment and possible pathophysiological mechanisms.

Comparison of I-FISH and G-banding for the detection of chromosomal abnormalities during the evolution of myelodysplastic syndrome.

Myelodysplastic syndrome (MDS) patients with a normal karyotype constitute a heterogeneous group from a biological standpoint and their outcome is often unpredictable. Interphase fluorescence in situ hybridization (I-FISH) studies could increase the rate of detection of abnormalities, but previous reports in the literature have been contradictory. We performed I-FISH and conventional karyotyping (G-banding) on 50 MDS patients at diagnosis, after 6 and 12 months or at any time if a transformation to acute myeloid leukemia (AML) was detected. Applying a probe-panel targeting the centromere of chromosomes 7 and 8, 5q31, 5p15.2 and 7q31, we observed one case with 5q deletion not identified by G-banding. I-FISH at 6 and 12 months confirmed the karyotype results. Eight cases transformed to AML during follow-up, but no hidden clone was detected by I-FISH in any of them. The inclusion of I-FISH during follow-up of MDS resulted in a small improvement in abnormality detection when compared with conventional G-banding.

Association of loss of heterozygosity with cytogenetic abnormalities in acute myeloid leukemia and myelodysplastic syndrome.

Deletions on chromosomes 5 and 7 are frequently seen in myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). It is assumed that these deletions indicate loss of tumor suppressor genes on these chromosomes and until these tumor suppressor genes are identified, the functional consequences of these deletions and the molecular basis of these myeloid disorders cannot be completely understood. We evaluated loss of heterozygosity (LOH) in 44 patients (18 MDS and 26 AML, diagnosed according to WHO classification criteria) at diagnosis, using a four-microsatellite marker panel: an intragenic marker on the 7th intron of gene IRF-1 of the 5q31.1 region and three markers located inside the 7q31.1 region and correlated the LOH with karyotype abnormalities. The microsatellites chosen corresponded to chromosome regions frequently deleted in MDS/AML. The samples with Q (peak area) less than or equal to 0.50 were indicative of LOH. The percent of informative samples (i.e., heterozygous) for the intragenic microsatellite in gene IRF-1 and in loci D7S486, D7S515 and D7S522 were 66.6, 73.7, 75.5, and 48.8%, respectively. Cytogenetic abnormalities by G-banding were found in 36% (16/44) of the patients (2 of 18 MDS and 14 of 26 AML patients). We found a significantly positive association of the occurrence of LOH with abnormal karyotype (P < 0.05; chi-square test) and there were cases with LOH but the karyotype was normal (by G-banding). These data indicate that LOH in different microsatellite markers is possibly an event previous to chromosomal abnormalities in these myeloid neoplasias.

Cytogenetic studies of Brazilian pediatric myelodysplastic syndrome cases: challenges and difficulties in a large and emerging country

Myelodysplastic syndromes (MDS) and juvenile myelomonocytic leukemia (JMML) are rare hematopoietic stem cell diseases affecting children. Cytogenetics plays an important role in the diagnosis of these diseases. We report here the experience of the Cytogenetic Subcommittee of the Brazilian Cooperative Group on Pediatric Myelodysplastic Syndromes (BCG-MDS-PED). We analyzed 168 cytogenetic studies performed in 23 different cytogenetic centers; 84 of these studies were performed in patients with confirmed MDS (primary MDS, secondary MDS, JMML, and acute myeloid leukemia/MDS+Down syndrome). Clonal abnormalities were found in 36.9% of the MDS cases and cytogenetic studies were important for the detection of constitutional diseases and for differential diagnosis with other myeloid neoplasms. These data show the importance of the Cooperative Group for continuing education in order to avoid a late or wrong diagnosis.

Does soy increase blood counts in myelodysplastic syndromes? / Será que a soja aumenta as contagens sanguíneas em síndrome mielodisplásica?

Myelodysplastic syndromes (MDS) are a group of clonal stem cell diseases characterized by ineffective hematopoiesis, bone marrow hyperproliferation, cytopenias in peripheral blood and risk of transformation into acute leukemia. We decided to investigate the effects of a soy concentrate on MDS patients based on the follow-up results of a 61 year-old Japanese female patient who was diagnosed with MDS and refractory cytopenia with multilineage dysplasia in 2003 (hemoglobin = 11g/dL; white blood cells count = 2,500/uL and platelets = 25,000/uL; marrow with mild dysplasia and normal karyotype; paroxysmal nocturnal hemoglobinuria was excluded). She started using soy as a dietary supplementation in May 2004 and presented a gradual increment in blood counts, achieving normalization approximately eight months afterwards. Among the soy components, the main compounds with anti-carcinogenic activity are the isoflavones (genistein and daidzein). Based on these lines of evidence, we proposed to administer daily a standard soy concentrate to 14 MDS out-patients for a minimum period of three months and maximum of 12 months, in an attempt to evaluate prospectively the possible increase in hemoglobin, neutrophils and platelet counts. A historical control group was used to compare results. The use of a soy concentrate in a standardized manner was associated with an increase in neutrophil and/or platelet counts in some cases, but spontaneous increments were also observed in historical controls. This preliminary study does not allow establishing a relation between soy supplementation and blood cell count increase.

As síndromes mielodisplásicas (SMD) são um grupo das doenças clonais de células-tronco caracterizado por hematopoese ineficaz, hiperproliferação de medula óssea, citopenias no sangue periférico e risco de transformação para leucemia aguda. Decidimos investigar os efeitos de um concentrado de soja em pacientes com SMD com base no fato de termos o seguimento de uma paciente japonesa, de 61 anos de idade, que foi diagnosticada em 2003 com SMD, citopenia refratária com displasia subtipo multilinhagens (hemoglobina = 11 g/dL; contagem de glóbulos brancos = 2.500/uL e plaquetas = 25.000/uL; medula com displasia leve e cariótipo normal; hemoglobinúria paroxística excluída), e que começou a usar a soja como suplemento alimentar em maio de 2004, apresentando gradual aumento da contagem das células sanguíneas, atingindo a normalização cerca de oito meses depois. Entre os componentes da soja, os principais compostos com propriedades anticarcinogênese são as isoflavonas (Ge nisteína e daidzeína). Com base nessas linhas de evidência, foi proposto oferecer diariamente um concentrado de soja padrão, por um período mínimo de três meses e máximo de doze meses, a 14 pacientes ambulatoriais, na tentativa de avaliar, prospectivamente, o possível aumento de hemoglobina, neutrófilos e plaquetas. Um grupo controle histórico foi utilizado para comparar os resultados. O uso de um concentrado de soja de forma padronizada foi associado ao aumento na contagem de neutrófilos e/ou de plaquetas em alguns casos, mas aumentos espontâneos também foram observados em controles históricos. Este estudo preliminar não permite estabelecer relação entre o uso de soja e o aumento na contagem sanguínea.

Comparison of I-FISH and G-banding for the detection of chromosomal abnormalities during the evolution of myelodysplastic syndrome

Myelodysplastic syndrome (MDS) patients with a normal karyotype constitute a heterogeneous group from a biological standpoint and their outcome is often unpredictable. Interphase fluorescence in situ hybridization (I-FISH) studies could increase the rate of detection of abnormalities, but previous reports in the literature have been contradictory. We performed I-FISH and conventional karyotyping (G-banding) on 50 MDS patients at diagnosis, after 6 and 12 months or at any time if a transformation to acute myeloid leukemia (AML) was detected. Applying a probe-panel targeting the centromere of chromosomes 7 and 8, 5q31, 5p15.2 and 7q31, we observed one case with 5q deletion not identified by G-banding. I-FISH at 6 and 12 months confirmed the karyotype results. Eight cases transformed to AML during follow-up, but no hidden clone was detected by I-FISH in any of them. The inclusion of I-FISH during follow-up of MDS resulted in a small improvement in abnormality detection when compared with conventional G-banding.

Association of loss of heterozygosity with cytogenetic abnormalities in acute myeloid leukemia and myelodysplastic syndrome

Deletions on chromosomes 5 and 7 are frequently seen in myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). It is assumed that these deletions indicate loss of tumor suppressor genes on these chromosomes and until these tumor suppressor genes are identified, the functional consequences of these deletions and the molecular basis of these myeloid disorders cannot be completely understood. We evaluated loss of heterozygosity (LOH) in 44 patients (18 MDS and 26 AML, diagnosed according to WHO classification criteria) at diagnosis, using a four-microsatellite marker panel: an intragenic marker on the 7th intron of gene IRF-1 of the 5q31.1 region and three markers located inside the 7q31.1 region and correlated the LOH with karyotype abnormalities. The microsatellites chosen corresponded to chromosome regions frequently deleted in MDS/AML. The samples with Q (peak area) less than or equal to 0.50 were indicative of LOH. The percent of informative samples (i.e., heterozygous) for the intragenic microsatellite in gene IRF-1 and in loci D7S486, D7S515 and D7S522 were 66.6, 73.7, 75.5, and 48.8 percent, respectively. Cytogenetic abnormalities by G-banding were found in 36 percent (16/44) of the patients (2 of 18 MDS and 14 of 26 AML patients). We found a significantly positive association of the occurrence of LOH with abnormal karyotype (P < 0.05; chi-square test) and there were cases with LOH but the karyotype was normal (by G-banding). These data indicate that LOH in different microsatellite markers is possibly an event previous to chromosomal abnormalities in these myeloid neoplasias.