Marked thrombocytosis in a child with advanced myelodysplastic syndrome.

Myelodysplastic syndromes (MDS) are clonal disorders characterized by ineffective hematopoiesis with rare occurrence in childhood. Conversely to adult affected patients, refractory anemia with ringed sideroblasts and the 5q-syndrome, which are associated with thrombocytosis are virtually absent in the pediatric age group. We describe the case of an 1-year-old boy with advanced MDS, specifically refractory anemia with excess of blasts who presented with leukocytopenia and anemia but marked thrombocytosis at diagnosis. Thrombocytosis resolved without therapy. This case illustrates the relationship between MDS and myeloproliferative disorders.