The current perspective of low-grade myelodysplastic syndrome in children.

Myelodysplastic syndrome (MDS) without increased blasts, i.e., low-grade MDS, is the most common subtype of pediatric MDS and has characteristics different from adult form of the disease. Although histological findings of bone marrow (BM) biopsies suggest that low-grade MDS is a morphologically distinctive entity, a subset of pediatric low-grade MDS may clinically overlap with aplastic anemia (AA), such as high likelihood of hypocellular marrow and normal karyotype. In addition, children with low-grade MDS are as likely to respond to immunosuppressive therapy as those with AA, which indicates that a part of these disorders might share a common pathogenesis, that is, T cell-mediated inhibition of hematopoiesis. In contrast, a small part of children with low-grade MDS experience disease progression to advanced MDS. Given that the clinical courses of pediatric low-grade MDS are heterogeneous, assessing prognostic values of clinical, morphological, histological and cytogenetic findings is critical. Thus far, monosomy 7 and multilineage dysplasia have been suggested as prognostic factors that could predict disease progression. Treatment strategy will be optimized based on more precise prognostic factors. In the future, molecular findings may also help prognostification in children with hypoplastic BM disorders.