Primary myelofibrosis

Lore & Background

Primary myelofibrosis (PMF) is a clonal neoplastic disorder of hematopoiesis, most often driven by somatic mutations in the JAK2, CALR, or MPL genes. The JAK2 V617F mutation, found in about half of patients, causes constitutive activation of signaling pathways that control blood cell production. Mutant megakaryocytes release growth factors such as PDGF and TGF-β1, stimulating fibroblasts to secrete excess collagen and reticulin, leading to progressive bone marrow fibrosis.

Reader's Guide

The significance of primary myelofibrosis lies in its classification as a myeloproliferative neoplasm and its distinct pathological features. In 2016, prefibrotic primary myelofibrosis was formally recognized as a distinct condition that often progresses to overt PMF, differentiated by fibrosis grade. The disease causes extramedullary hematopoiesis, primarily in the spleen, leading to massive splenomegaly and pancytopenia. While allogeneic stem cell transplantation is the only curative option, it carries significant risks; other treatments are largely supportive. The JAK2 V617F mutation is central to pathogenesis, and smoking has been associated with increased risk. Understanding PMF has advanced knowledge of clonal hematopoiesis and cytokine-driven fibrosis.

Did You Know?

• Approximately 90% of those with myelofibrosis have a mutation in JAK2, CALR, or MPL.
• The JAK2 V617F mutation involves a valine-to-phenylalanine substitution at position 617.
• Smoking has been associated with the development of myeloproliferative neoplasms, including PMF.
• Cutaneous myelofibrosis is a rare skin condition characterized by dermal and subcutaneous nodules.