The highly selective oral Janus kinase (JAK) 1/JAK2 inhibitor ruxolitinib has been shown in two phase 3 studies to reduce splenomegaly and symptom burden in patients with intermediate-2 or high-risk disease compared with placebo or best available therapy (BAT) [33–37] with concomitant improvements in functional status and various measures of quality of life [38, 39]. Here, JAK2 is linked to Splenomegaly.