The preleukemic syndromes (hematopoietic dysplasia) in childhood

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 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.

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.

Acute myelogenous leukaemia in children

Acute myelogenous leukaemia in childhood is considerably more resistant to chemotherapy than the acute lymphocytic leukaemias. Recently, more aggressive therapy has improved the outlook for children with this difficult form of leukaemia. Long-term disease-free survival of children achieving remission has been reported to be more than 40% in some studies. This paper reviews both the present concept of leukaemogenesis as well as some of the more recent therapeutic studies on childhood AML.

Preleukemic syndromes and other syndromes predisposing to leukemia

The myelodysplastic and myeloproliferative syndromes are syndromes in childhood that may precede leukemia. Clinical and biologic features are reviewed in this article. Although rare, they offer an unique opportunity to observe the evolution of leukemia and give clues that are helping us to understand the leukemogenic process.

Acute lymphoblastic leukaemia after bone marrow transplantation for aplastic anaemia

An 11.5-year-old girl developed acute lymphoblastic leukaemia 7 months after bone marrow transplantation for severe aplastic anaemia. Before transplantation there were neither morphologic nor cytogenetic abnormalities to suggest preleukaemia. The conditioning regimen consisted only of cyclophosphamide. At the time of development of acute lymphoblastic leukaemia, chromosome analysis showed the blasts to be of host origin with clonal abnormalities including monosomy 7. Such a preleukaemic syndrome presenting as severe aplastic anaemia is a very rare event (the case reported here is the only one of 436 patients in Seattle) and cannot be reliably excluded before transplantation.

Myelodysplastic syndromes. A clinical and pathologic analysis of 109 cases

A total of 109 patients with myelodysplastic syndromes (MDS) was analyzed to determine the clinical and pathologic features of the five recently defined French-American-British Cooperative Group (FAB) subtypes, and to assess the utility of this classification system in predicting survival, evolution to acute nonlymphocytic leukemia (ANLL), and cause of death. All patients with MDS presented with anemia; additional cytopenias were present in patients with refractory anemia with excess blasts (RAEB), chronic myelomonocytic leukemia (CMML) and refractory anemia with excess blasts in transformation to ANLL (RAEB/Tr). Thirty-two patients received some form of antileukemic therapy for MDS. ANLL developed in 16 of the 77 remaining untreated patients, including 18% (2/11), 0% (0/21), 22% (5/23), 33% (2/6), and 44% (7/16) of patients with refractory anemia (RA), refractory anemia with ring sideroblasts (RARS), RAEB, CMML, and RAEB/Tr, respectively (P = 0.02). The FAB subtype was highly predictive of survival with median survivals ranging from 71 months for RARS to 5 months for RAEB/Tr (P = less than 0.0001). Patients with RAEB, CMML, and RAEB/Tr frequently died of direct consequences of MDS, while patients with RA and especially RARS generally survived or died from unrelated disorders (P = less than 0.0001). MDS encompass a spectrum of disorders. RA and RARS, are relatively indolent and often do not lead to the patient's demise. RAEB, CMML, and RAEB/Tr are aggressive disorders which are often responsible for the patient's death whether or not actual progression to overt leukemia occurs. FAB subtype predicts survival, evolution to ANLL, and cause of death, although the five morphologic subtypes appear to separate into only two disease groups, especially with regard to survival and cause of death.

Myelodysplastic syndromes in childhood: three case reports

Three children with myelodysplastic syndromes (MDS) are described following the diagnostic criteria proposed by the FAB-cooperative group. Two of the children were of Turkish origin. Two cases fit the criteria for 'refractory anaemia with excess of blasts in transformation'. The other one is most consistent with 'chronic myelomonocytic leukaemia'. The patients received 'ANLL type' induction. One died during induction, two were grafted, of whom one survives.

Preleukemias

A chromosomally abnormal clone is demonstrable in the bone marrow of a significant number of patients with hemic disorders that carry an increased risk for the subsequent development of leukemia. These "preleukemia" states include a variety of cytopenias, myeloproliferative disorders, and childhood syndromes. The cytogenetic alterations that occur nonrandomly in these dyscrasias are often similar to those observed in acute nonlymphocytic leukemia and in the accelerated phase of chronic granulocytic leukemia: monosomy for chromosome 7; trisomy for 8,9,21, and the long arm of 1(1q); deletions of 5 and 20 (5q-, 20q-); and an isochromosome derived from 17 (iso 17q). These findings support the view that despite clinical differences, these various preleukemic disorders are all characterized by the presence in the hematopoietic tissues of a clone of cells derived from an altered hemic stem cell. Furthermore, the data suggest that preleukemia, chronic leukemia, and acute leukemia may be fundamentally similar diseases, differing primarily in the rate at which the aberrant clone is expanding. Chromosome studies may be of prognostic value in the cytopenic preleukemias. Patients with abnormalities show a decreased survival and are at increased risk for progression to acute nonlymphocytic leukemia. In the myeloproliferative disorders and the preleukemic childhood disorders, cytogenetic alterations are not clearly predictive, and aberrant clones may persist for years without clinical progression.