While Shomali et al. were the first to identify an acquired somatic mutation also in the pseudokinase domain (R629_S632delinsSA) with activation of the JAK1-STAT3/STAT5 pathway and clonal eosinophilic neoplasm [261], Takeichi et al. reported a heterozygous JAK1 mutation of unclear somatic or germline origin, with both mutations showing (hyper-)eosinophilia [262]. Here, JAK1 is linked to Increased total eosinophil count.