Childhood myelodysplastic syndromes: clinical features, cytogenetics and prognosis

Childhood myelodysplastic syndrome

Myelodysplastic syndrome (MDS) comprises of a heterogeneous group of bone marrow disorders resulting from a clonal stem cell defect characterised by cytopenias despite a relatively hypercellular marrow, ineffective hematopoiesis, morphological dysplasia in the marrow elements, no response to hematinics such as iron, B12 or folic acid and risk of progression to leukemia. Myelodysplastic syndrome in childhood is extremely rare and accounts for less than 5% of all hematopoietic neoplasms in children below the age of 14 y. The primary MDS in children, also known as de novo MDS differs from secondary MDS which generally follows congenital or acquired bone marrow (BM) failure syndromes as well as from therapy related MDS, commonly resulting from cytotoxic therapy. MDS associated with Down syndrome which accounts for approximately one-fourth of cases of childhood MDS is now considered a unique biologic entity synonymous with Down syndrome-related myeloid leukemia and is biologically distinct from other cases of childhood MDS. Refractory cytopenia of childhood (RCC) is the commonest type of MDS. Genetic changes predisposing to MDS in childhood remain largely obscure. Monosomy 7 is by-far the commonest cytogenetic abnormality associated with childhood MDS; however most cases of RCC show a normal karyotype. Complex cytogenetic abnormalities and trisomy 8 and trisomy 21 are also occasionally observed. The most effective and curative treatment is Hematopoietic stem cell transplantation and this is particularly effective in children with the monosomy 7 genetic defect as well as those displaying complex karyotype abnormalities provided it is instituted early in the course of the disease.

Myelodysplastic syndromes in children: a critical review of issues in the diagnosis and classification of 887 cases from 13 published series

CONTEXT

Pediatric myelodysplastic syndromes (MDSs) are uncommon disorders, which may be difficult to diagnose, particularly in the absence of increased blasts. Pediatric MDSs have several unique features including their association with inherited/constitutional disorders in approximately one third of patients. The classification of pediatric MDSs has undergone significant evolution in the past 20 years.

OBJECTIVE

To critically review existing classifications of pediatric MDSs and to evaluate their applicability on previously published large series.

DATA SOURCES

Previously published pediatric MDS series containing more than 10 patients from the English literature between 1982 and 2005.

CONCLUSIONS

Data were available on 887 patients from 13 published series. Most cases (68.7%) were idiopathic/de novo, 23.9% were associated with constitutional/inherited disorder, and 7.4% were therapy related. Approximately 10% of cases could not be classified by the French-American-British classification. Eighty-seven percent of unclassified cases were appropriately classified using the World Health Organization classification (2001), whereas 96% of them were classified with the modified World Health Organization classification for pediatric MDSs (2003). The impact of cytogenetics and constitutional/inherited disorders on the biology and outcome of the disease needs to be studied further.

Myelodysplastic syndromes in children. A critical review of the clinical manifestations and management

The FAB group has defined myelodysplasia in adults but direct application of this categorization to children has been controversial. Consequently, to outline the natural history of the disease better we have retrospectively analysed case reports and series published in English between 1982 and 1996. This study also included children with juvenile chronic myelomonocytic leukaemia (JCML) and monosomy 7 (Mo7). 340 patients were described in 27 publications. The mean presentation age was 5.91 (SD 5.04) years, and 34.9% were female. Constitutional alterations were described in 68 (20%) where refractory anemia (RA) and RA with excess of blasts (RAEB) predominated and were associated with a significantly longer survival. Among all patients progression to higher forms of MDS was noted in 61 (18%). Cytogenetic anomalies were detected in 59% of 227 children, and in 67 it was to Mo7. Amid those with Mo7, the clinical and laboratory characteristics as well as survival, closely followed their FAB type. Of the treatment options described, survival was significantly higher in those who underwent bone marrow transplant (BMT) (46.9%; P = 0.00021). Among children with JMML (CMML/JCML) not receiving a BMT, time to death was shortest in those best described as JCML (absence of constitutional and karyotypic derangement, thrombocytopenia and elevated Hb F). We conclude that children with constitutional abnormalities survive longer, Mo7 disorders are clinically and morphologically heterogeneous and should not be grouped into a single entity and that CMML and JCML may have biological differences. Finally, BMT remains the treatment of choice for those with primary MDS, as intensive chemotherapy is no better than supportive measures.

Cytogenetics investigation in childhood chronic myeloid leukemia

Cytogenetics investigations, mostly from peripheral blood, were carried out in 30 children with CML. Amongst a sample of 30 patients, 18 had chronic myeloid leukemia of adult variety (ACML), while the remaining 12 children had the juvenile type of chronic myeloid leukemia (JCML). Sixteen (88.9%) out of the 18 patients suffering from ACML tested positive for the classical Philadelphia chromosome translocation t(9; 22). Of the remaining two ACML patients, one tested positive for t(9; 13; 22) while no visible chromosomal changes were observed in the other patient. The activity of Nucleolar Organizer Region (NOR) was significantly reduced in 11 (61.1%) of the 18 patients suffering from ACML, when compared to that of 21 normal healthy controls. Ten out of the 12 patients suffering from JCML had normal karyotypes, while monosomy 8 and 21 q deletion were seen in the remaining two patients respectively. Amongst the 30 CML patients, chromosomal abnormalities were observed in 19 patients. Variant Philadelphia chromosome translocation (9; 13; 22) and monosomy B were observed in ACML and JCML, respectively. In two ACML patients, cytogenetic studies were helpful in diagnosis of the disease.

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.