Myelofibrosis is a bone marrow disorder in which hematopoietic tissue is progressively replaced by fibrotic connective tissue, driven — in the primary form — by a gain-of-function mutation in JAK2 that hyperactivates the JAK-STAT signaling pathway, causing megakaryocyte proliferation and cytokine (including fibroblast growth factor) release that activates fibroblasts to deposit excess connective tissue; the resulting loss of marrow hematopoietic capacity triggers compensatory extramedullary hematopoiesis in the liver, spleen, and lungs, which is typically insufficient to prevent pancytopenia. This is a topic in hematology within internal medicine, illustrating the broader principle of myeloproliferative neoplasms arising from dysregulated JAK-STAT signaling and secondary bone marrow fibrosis, and it can also arise secondarily from other myeloproliferative conditions such as essential thrombocythemia and polycythemia vera.
Myelofibrosis is a bone marrow disorder in which hematopoietic tissue is progressively replaced by fibrotic connective tissue, driven — in the primary form — by a gain-of-function mutation in JAK2 th…