Such overall reduced blood counts of (most) normal residual immune-cell subsets may reflect a more profound immunodeficiency status in STAT3-mutated LGLL, which is not restricted to neutrophils, but also affects other myeloid cells—i.e., eosinophils, nonclassical monocytes, and dendritic cells—as well as lymphoid cells—i.e., the major T-cell subsets and NK cells. Here, STAT3 is linked to immune system disorder.