These include a prominent hepatomegaly (Figure 2A and 2B) with peripheral leukocytosis that is heavily skewed towards myeloid (monocyte, neutrophil) lineages but with some lymphocytosis as well (Figure 2D), and hypersensitivity of BM cells to cytokines, including GM-CSF (Figure 4C), a hallmark of JMML [28]. Here, CSF2 is linked to juvenile myelomonocytic leukemia.