JAK1 and acquired polycythemia vera: A post-hoc analysis of phase III clinical trials reported a mean weight gain of 3.9 kg in patients with MF treated with ruxolitinib at 24 weeks9; however, a detailed examination of the distribution of weight gain, and the metabolic implications of JAK1/2 inhibition with ruxolitinib in patients with MF and PV, has not been described.