Pediatric myelodysplastic/myeloproliferative neoplasms and related diseases

Myelodysplastic/myeloproliferative neoplasms (MDS/MPN) are clonal hematopoietic disorders with myeloproliferative features, varying degrees of dysplasia and cytopenias, and increased propensity for progression to acute myeloid leukemia (AML). MDS/MPN are uncommon in the pediatric age group, and best exemplified by Juvenile myelomonocytic leukemia (JMML), a rare but aggressive leukemia of early childhood. Remarkable progress has been made in understanding the genetic basis of JMML leading to improved diagnostic criteria and better management. It is now understood that JMML is associated with somatic or germ line mutations in NF1, NRAS, KRAS, PTPN11, and CBL in greater than 90 % of cases with the common downstream mechanism being uncontrolled activation of the RAS/MAPK pathway. More recently, KRAS and NRAS mutations have also been identified in RAS-associated autoimmune leukoproliferative disorder (RALD), which shares some clinical, hematopathological, and genetic features with JMML, but has an indolent clinical course. Hematopoietic stem cell transplant (HSCT) is currently the only curative therapy for JMML, although newer therapeutic agents are currently in clinical trials. This review will focus primarily on the current clinical features, diagnostic criteria, pathologic features, and therapy of JMML and provide a brief description of RALD.