The underlying cause of<unk>  is unknown (idiopathic disease). There is an association between mutations to the JAK2, CALR, or MPL gene and myelofibrosis. Approximately 90% of those with myelofibrosis have one of these mutations and 10% carry none of these mutations. These mutations are not specific to myelofibrosis, and are linked to other myeloproliferative neoplasms, specifically polycythemia vera and essential thrombocythemia. The V617F mutation to the JAK2 protein is found in approximately half of individuals with<unk> . The V617F mutation is a change of valine to phenylalanine at the 617 position. Janus kinases (JAKs) are non-receptor tyrosine kinases essential for the activation of signaling that is mediated by cytokine receptors lacking catalytic activity. These include receptors for erythropoietin, thrombopoietin, most interleukins and interferon. JAK2 mutations are significant because JAK2 plays a role in controlling production of blood cells from hematopoietic stem cells. The V617F mutation appears to make hematopoietic cells more sensitive to growth factors that need JAK2 for signal transduction, which include erythropoietin and thrombopoietin. The MPL gene codes for a protein that acts as a receptor for thrombopoietin. A mutation in that gene, known as a W515 mutation, leads to the production of an abnormal thrombopoietin receptor protein, which results in the overproduction of abnormal megakaryocytes. The abnormal megakaryocytes stimulate other cells, the fibroblasts, to produce collagen in the bone marrow, by secreting PDGF and TGF-β1.
Primary myelofibrosis
Prefibrotic primary myelofibrosis
Acute panmyelosis with myelofibrosis
Chronic neutrophilic leukemia
Acute myeloid leukemia
Leukemoid reaction
Myelodysplastic syndrome
Chronic lymphocytic leukemia