Myelodysplastic syndromes

Definition

Myelodysplastic syndromes (MDS) in childhood encompasses a diverse group of clonal hematopoietic stem cell disorders, characterized by ineffective hematopoiesis with morphologic dysplasia, peripheral cytopenia, and an increased propensity to evolve into acute leukemia. MDS can arise either de novo in a previously healthy child (primary MDS), or develop in a child with a known predisposition as secondary MDS. In adult patients, most of the secondary MDSs are therapy-related, following cytotoxic therapy for prior neoplastic or non-neoplastic conditions. Secondary MDS in childhood includes many cases associated with constitutional bone marrow failure disorders, MDS evolved from acquired aplastic anemia, and familial MDS (Table 14.1), in addition to therapy-related MDS. It is noteworthy that the distinction of primary MDS and secondary MDS may not be clear cut in pediatric patients, since some of “primary MDS” may have an underlying, yet unknown, genetic defect predisposing them to MDS at a young age.

Epidemiology

Pediatric MDS is a rare hematologic malignancy of childhood. The reported incidence of pediatric MDS comprises 1.1 to 8.7% of hematologic malignancies of childhood, with an annual incidence of 1.8 per million in children of 0–14 years of age [1]. It constitutes 4% of cases, and is the third most common hematologic malignancy in children, following acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML). In contrast to adult MDS that shows a male predominance (1.7 : 1), MDS in children affects males and females with an equal frequency.