Collectively, we observed both quantitative (reduction in numbers of ECs and MSCs) and qualitative (inflammation and TNF signaling) disruption of the BM microenvironment in Flt3-ITD mice, which likely underlie the observed extrinsic suppression of HSCs, in agreement with other studies implying that hematologic malignancies dysregulate HSC niches (Schepers et al., 2015). Here, FLT3 is linked to hematologic disorder.