MECOM and Myelodysplasia: In the follow up of the clinical trial a substantial gene transfer in neutrophil cells had produced a high number of functional phagocytes, however, after the initial resolution of bacterial and fungal infections, both subjects showed silencing of transgene expression due to methylation of the viral promoter, and myelodysplasia with monosomy 7 as a result of insertional activation of ecotropic viral integration site 1 (EVI1).