STAT3 and Decreased total neutrophil count: Activating somatic mutations in the STAT3 gene, the hallmark of CD8+ T-LGLL, occurs in 40–50% of patients6–11, where the majority of variants (e.g., Y640F, D661V, and D661Y) are located in the SH2 domain of STAT3. Although the clinical features of patients with mutated and wild-type STAT3 overlap, (severe) neutropenia and autoimmune manifestations are more common in mutated STAT3 cases6,10,12–14.