Myelodysplasia

Update on childhood neutropenia: molecular and clinical advances

Congenital and inherited disorders are important differential diagnoses of neutropenia, particularly in neonates and children, although acquired causes are more common. This article focuses on recent advances in understanding the cellular and molecular defects in inherited neutropenias as well as issues that are related to clinical presentation, diagnosis, and complications.

Paediatric myelodysplastic syndrome (MDS) and juvenile chronic myelogenous leukaemia (JCML) detected by cytogenetic and FISH techniques

This report presents two rare cases, one of paediatric myelodysplastic syndrome (MDS) and the other juvenile chronic myeloid leukaemia (jCML). In the first case, there were clinical and biological features of MDS-refractory anaemia with excess blasts (RAEB). The bone marrow (BM) karyotype demonstrated a monosomy 7 which was confirmed by fluorescence in situ hybridization (FISH). In addition, FISH analysis showed that an alpha-satellite DNA sequence had been transferred from chromosomes 13/21 to one homologue of chromosomes 22. The BCR-ABL rearrangement was negative. In the second case, at diagnosis, the karyotype was 46,XX. FISH analysis with the simultaneous and individual application of abl and bcr probes for chromosome 9 and 22, respectively, revealed the presence of the BCR-ABL rearrangement in addition to an extra ABL sequence locating chromosome 20. A clone that was BCR-ABL gene rearrangement negative but with an extra ABL DNA sequence on chromsome 20, and another clone that was BCR-ABL gene rearrangement negative were detected by DC-FISH and uni-colour (UC-) FISH analysis. No monosomy 7 was detected by conventional cytogenetic or FISH analyses.

Mutations of the NF1 Gene in Children With Juvenile Myelomonocytic Leukemia Without Clinical Evidence of Neurofibromatosis, Type 1

Juvenile myelomonocytic leukemia (JMML) is a pediatric myelodysplastic syndrome that is associated with neurofibromatosis, type 1 (NF1). The NF1 tumor suppressor gene encodes neurofibromin, which regulates the growth of immature myeloid cells by accelerating guanosine triphosphate hydrolysis on Ras proteins. The purpose of this study was to determine if the NF1gene was involved in the pathogenesis of JMML in children without a clinical diagnosis of NF1. An in vitro transcription and translation system was used to screen JMML marrows from 20 children for NF1mutations that resulted in a truncated protein. Single-stranded conformational polymorphism analysis was used to detect RASpoint mutations in these samples. We confirmed mutations of NF1in three leukemias, one of which also showed loss of the normalNF1 allele. An NF1 mutation was detected in normal tissue from the only patient tested and this suggests that JMML may be the presenting feature of NF1 in some children. Activating RASmutations were found in four patients; as expected, none of these samples harbored NF1 mutations. Because 10% to 14% of children with JMML have a clinical diagnosis of NF1, these data are consistent with the existence of NF1 mutations in approximately 30% of JMML cases.

In vitro culture studies of childhood myelodysplastic syndrome: establishment of the cell line MUTZ-1

Myelodysplastic syndrome (MDS) in childhood is considered to be very rare and detailed pathobiological data are scarce. More biological information regarding MDS in children is clearly needed and in vitro culture studies provide one possibility for gaining further pathophysiological insights into this malignancy. Here, we incubated bone marrow samples from 30 children with MDS in liquid suspension culture in order to grow the transformed cells in vitro. In most cultures, the hematopoietic cells died quickly and only fibroblastic (stromal) background layers proliferated temporarily; several normal Epstein-Barr virus (EBV)-transformed B-lymphoblastoid cell lines (B-LCL) were established. Only in one instance, albeit from the peripheral blood and not from the bone marrow, could we establish a cell line, termed MUTZ-1, from the malignant cells of a 5-year-old girl with MDS (FAB subtype refractory anemia with excess of blasts). The MDS arose from a pre-existing Fanconi anemia and progressed quickly to an acute myeloid leukemia (FAB M2). Despite positivity for EBV, MUTZ-1 is not an EBV + B-LCL and further characterization of MUTZ-1 confirmed the derivation from the transformed clonal cells. Immunophenotyping showed a pre B-cell surface marker profile (CD10+ CD19+ cytoplasmic IgM+); receptor gene rearrangement analyses underlined the clonal B-cell nature of MUTZ-1 cells. MUTZ-1 cells exhibit a highly rearranged, unstable karyotype with a high frequency of spontaneous chromatid breaks and exchanges; del(5q) and additional rearrangements involving chromosome 5 [der(15)t(5;15)] were detected. The present data and results from a few other MDS-derived cell lines suggest that the transforming event in MDS seems to occur in an immature pluripotent progenitor cell. The new MDS-derived continuous cell line MUTZ-1 provides a useful in vitro model system for studies on the pathogenetic events leading to MDS.

Pediatric hyperfibrotic myelodysplasia: an unusual clinicopathologic entity

This study is presented to highlight a rare pediatric bone marrow pathology in which features of bone marrow dysplasia coexist with severe fibrosis in a clinical setting of fever, anemia, and organomegaly. Fourteen children (nine males, five females) clinically presented with fever, anemia, and hepatosplenomegaly. Extensive bone marrow fibrosis with dysplastic features was seen in their marrow precursor cells. Peripheral blood smears showed teardrop poikilocytes thrombocytopenia, and occasional blasts. In conclusion, pediatric hyperfibrotic myelodysplasia is a distinct clinicopathologic entity. Myeloproliferative and dysmyelopoietic syndromes are complex disorders that are interrelated and not always easily diagnosed only on morphologic grounds.

Cytogenetic abnormalities in pediatric myelodysplastic syndrome: a report of three cases

Three consecutive cases of pediatric myelodysplastic syndrome (MDS) diagnosed over a three-year period in Queen Mary Hospital, Hong Kong, were described. Depending on the classification system used, they comprised two cases of chronic myelomonocytic leukemia (CMMoL) of which one can be reclassified as juvenile chronic myeloid leukemia (JCML) and one cases of refractory anemia with excess of blasts (RAEB) or an alternative diagnosis of atypical CML. Cytogenetic abnormalities were detected in all of them on examination of bone marrow cells. Of the two CMMoL, one had monosomy 21, whereas the other had hypodiploidy. The patient with RAEB had a complex karyotype of 46,X,del(X)(q24),t(1;7) (p22;q32),add(15)(q26)(8). The balanced translocation (1;7) seen in this patient was exceedingly rare and, to the best of our knowledge, was reported only twice in the literature. The karyotypic abnormalities that we saw in our patients were not well recognized in pediatric MDS. This report emphasizes the importance of cytogenetic study in children suspected of suffering from MDS, which remains a rare disorder of childhood, and a need to rationalize current classification schemes.

Epidemiological and etiological aspects of myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are increasingly recognized as a cause of bone marrow failure, and are at least as frequent as acute myeloid leukemias. While the overall incidence is about 2-4/100,000/year, incidence figures rise steeply with age. Incidence rates of 20-30/100,000/year in persons over 70 demonstrate that MDS are among the most common hematological neoplasias in this age group. However, due to difficulties of diagnosis and classification, patient registration in population-based registers is far from complete. As a prerequisite for truly representative statistics, future revisions of disease classification systems must incorporate MDS as a separate group of disorders. The difficulties in conducting epidemiological studies also impede the identification of risk factors for the development of MDS. Current knowledge of occupational risk factors is also reviewed here. More rapid progress in our understanding of MDS may come from recent advances in methodology that have begun to shed some light on the cytogenetic and molecular aspects of leukemogenesis in general, and MDS in particular. Non-random chromosomal changes can be found in about 50% of cases at diagnosis, but they are probably late events in the evolution of MDS, reflecting the progressive genomic instability of the premalignant clone. Proto-oncogene mutations have also been suggested to be relevant to the pathogenesis of MDS, but longitudinal studies of point mutations of the N-ras proto-oncogene revealed that such events, although often associated with rapid deterioration and transformation to AML, also appear to be late events during the course of disease. Therefore, it remains a major challenge to identify those lesions that initiate the multistep development of preleukemia. As the incidence of MDS correlates strongly with age, it is reasonable to presume that age-dependent changes of the hematopoietic system may play a role in the initiation of MDS. Aging is probably associated with a compromised marrow reserve through reduction in the size of the stem cell pool. Through increased proliferative activity, the remaining stem cells may be particularly vulnerable to mutagenic insults. Immunological attack on stem cells, mitochondrial DNA mutations, and the regulatory influence of the hematopoietic microenvironment must also be considered as possibly contributing to the early stages of MDS.

Neurofibromatosis and childhood leukaemia/lymphoma: a population-based UKCCSG study

There is a well-known raised risk of leukaemia in children with neurofibromatosis type 1 (NF-1). We carried out the first detailed population-based study of leukaemia and non-Hodgkin lymphoma (NHL) associated with NF-1 in order to estimate the risk and elucidate the relationship between these conditions. Over the 17 year study period there were five cases of chronic myelomonocytic leukaemia (CMML) in patients with NF-1 (relative risk 221; 95% CI 71-514), 12 cases of acute lymphoblastic leukaemia (ALL) (relative risk 5.4; 95% CI 2.8-9.4) and five cases of NHL (relative risk 10.0; 95% CI 3.3-23.4). Marrow cytogenetics could be reviewed for seven patients. Specific abnormalities found were monosomy 21 in a child with CMML and 7p+, 17p- in a child with ALL. No abnormalities were reported of 17q, which includes the NF1 gene. CMML occurred predominantly in boys, who also had a family history of NF-1. ALL and NHL were more often found in children with no previous family history.

Myelodysplastic syndromes in childhood: description of seven cases

Seven children with a primary myelodysplastic syndrome were seen at our center over a 9-year period. Two presented with refractory anemia, three with refractory anemia with excess of blasts, and two with refractory anemia with excess of blasts in transformation. All children received supportive therapy, including blood transfusions in five of them. Three patients developed acute myeloid leukemia and were treated with intensive chemotherapy, followed by allogeneic or autologous marrow transplantation in the two responders. All three died of either infection or progressive disease. The other four patients are still alive a median of 71 months (range 38-130) after diagnosis. These results confirm the difficulties in managing patients with myelodysplastic syndromes.

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.

Primary myelodysplastic syndrome in children: the clinical experience in 33 cases

We describe the clinicomorphological features in 33 cases of primary myelodysplastic syndrome classified according to the FAB classification which presented to a single centre over a 12 year period. Presenting features were typically related to pancytopenia although hepatosplenomegaly and granulocytic sarcomas were far more prevalent than in the adult population. Morphological assessment of the peripheral blood and the bone marrow showed seven patients had refractory anaemia (RA), 13 patients had RA with excess of blasts (RAEB), nine patients had RAEB in transformation (RAEB-t) and four patients had chronic myelomonocytic leukaemia (CMML). The overall mean survival was short (9.9 months) in all the subgroups and the leukaemic transformation rate was high. None of the patients scored 0-1 according to the Bournemouth Scoring System; four patients scored 2 whereas 29 patients scored 3 to 4. We conclude that unlike adults, the myelodysplastic syndromes in children run an aggressive clinical course, irrespective of the FAB subtype, and the pathogenesis of these diseases in paediatric practice warrants scientific scrutiny. Intensive chemotherapy such as the one used in de novo-AML lead to complete remission in some children and these early results suggest that this should be the treatment of choice in paediatric MDS.

Myelodysplastic syndromes in childhood: a population based study of nine cases

Nine cases of de novo myelodysplastic syndromes (MDS) in childhood from a population based study are presented. The annual incidence of MDS was 3.4/1,000,000 in children less than 15 years old, corresponding to 8.7% of all haematological malignancies in childhood. Two patients had Down's syndrome. None of the remaining patients had constitutional anomalies. All patients were classified according to the FAB classification. Five patients presented with refractory anaemia (RA), only one of these did not progress, one showed clonal evolution, and the remaining three patients all progressed to refractory anaemia with excess of blasts (RAEB). Three patients presented with RAEB. Two progressed to overt leukaemia. The last patient was classified as chronic myelomonocytic leukaemia (CMML). Clonal cytogenetic abnormalities were detected in five patients, in three of them as monosomy 7. Five patients have died; two of progressive disease, two of infections, and one of haemorrhage, two of the latter three patients died during therapy induced cytopenia. Of the four patients still alive, one patient showed a complete remission after cyclosporine and later immunoglobulin therapy, one patient is a long-term survivor after allogeneic bone marrow transplantation, and one patient apparently obtained a spontaneous remission several months after chemotherapy.

Chronic myelomonocytic leukemia with t(13;14) in a child

Bone marrow cells from a child with chronic myelomonocytic leukemia showed an acquired, non-Robertsonian translocation between chromosomes 13 and 14, t(13;14)(q12.?2;q32.?3). This rearrangement has not previously been reported in childhood myeloproliferative or myelodysplastic disorders.