Primary myelofibrosis
Description
- MPN with clonal megakaryocyte + granulocyte proliferation -> reactive marrow fibrosis -> marrow failure + extramedullary haematopoiesis
- The fibrosis is polyclonal and reactive - fibroblasts responding to cytokines from the clone. Not part of the malignant clone, which is why it can regress on effective therapy
Forms
| Prefibrotic PMF (pre-PMF) | Grade 0-1 fibrosis, thrombocytosis, near-normal counts. *Mistaken for ET* - but worse survival and higher transformation |
| Overt PMF | Grade 2-3 fibrosis, cytopenias, splenomegaly, constitutional symptoms |
| Secondary MF | Post-PV MF, post-ET MF. Same phenotype, different prognostic score (MYSEC-PM) |
The clinical triad
- Constitutional symptoms - weight loss, drenching night sweats, fever, fatigue, bone pain, pruritus
- Massive splenomegaly - early satiety, LUQ pain, splenic infarct
- Cytopenias - anaemia is near-universal and dominates management
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