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.