Phenotypic switching to hypereosinophilia during cytoreductive therapy for transient abnormal myelopoiesis associated with Down syndrome

[摘要] Transient abnormal myelopoiesis (TAM) is a clonal hematologicaldisorder originating from fetal liver hematopoiesis associated withDown syndrome. The pathognomonic GATA1 mutation in conjunction with the gene dosage effect of 21 trisomy induces clonal proliferation of megakaryoblasts [1], but little is known for the celldifferentiation plasticity, especially phenotypical switching duringcytoreductive therapy. A male infant was born through emergencycaesarean section due to fetal distress at 30 weeks of gestation withApgar scores of 1 and 6 at 1 and 5 min, respectively. He weighed1,338 g and presented with characteristic facial dysmorphism, hepatomegaly and bleeding diathesis. Cytogenic analysis showed trisomy21. A complete blood count showed a haemoglobin of 7.8 g/dl, aplatelet count of 742 × 109/L and a leukocyte count of 326 × 109/L.