JAK1 and myeloproliferative neoplasm: According to the literature, Ruxolitinib, a JAK1/JAK2 inhibitor, has been shown to reduce symptoms related to proinflammatory cytokine release in other myeloproliferative neoplasms.<h4>Case presentation</h4>Here we present a case using Ruxolitinib for disabling constitutional symptoms despite complete bone marrow response in a patient with aggressive systemic mastocytosis.