JAK1/2 inhibitors, such as the approved drug ruxolitinib inhibit signaling of some inflammatory cytokines such as IL-6 and other inflammatory or proliferation promoting cytokines that signal through JAK1 and/or JAK2, have been shown to suppress abnormal clonal expansion and reduce splenomegaly in MF, but do not substantially reduce the allelic burden of the mutated JAK clone or prevent or reverse bone marrow fibrosis in the majority of patients. Here, JAK1 is linked to Splenomegaly.