PassFinals
Haematology & Oncology

Myelofibrosis

A myeloproliferative neoplasm in which a clonal marrow drives fibroblasts to lay down reticulin and collagen, so the marrow is progressively replaced by fibrosis; blood production shifts to the spleen and liver (extramedullary haematopoiesis), producing massive splenomegaly, a leukoerythroblastic film with tear-drop red cells, and constitutional symptoms.

In a nutshell

Myelofibrosis causes fibrotic marrow failure, extramedullary haematopoiesis, splenomegaly and constitutional symptoms. Confirm the subtype and prognosis, discuss transplant early in suitable higher-risk disease, and choose symptom- and anaemia-adapted JAK-inhibitor/supportive treatment.

Classic presentation

An older adult with anaemia, fatigue, night sweats, weight loss, bone pain or massive splenomegaly, often with a leukoerythroblastic film.

Key points

  • MF may be primary or follow PV/ET.
  • Marrow fibrosis, atypical megakaryocytes and clonal mutations support diagnosis.
  • Prognostic scoring and transplant fitness must be assessed early.
  • Ruxolitinib, momelotinib and fedratinib have defined NICE populations.
  • Anaemia, infection, bleeding and symptom burden need active supportive care.

First-line investigation

FBC and film, marrow biopsy, molecular testing, spleen assessment and specialist prognostic scoring.

Management

Confirm and prognosticate

  • Confirm primary, post-PV or post-ET MF with marrow, molecular and clinical assessment, then apply a validated prognostic approach and assess fitness.1,2

Consider transplant in selected people

  • Discuss allogeneic transplant early for suitable higher-risk disease, balancing disease biology, age, comorbidity, donor options and patient goals.2

Treat splenomegaly and symptoms

  • Use a JAK-inhibitor strategy selected by risk, anaemia, prior therapy, symptom burden and current NICE criteria.4,5,7

Manage marrow failure and symptoms

  • Treat anaemia, infection, bleeding, nutrition, pruritus, pain and constitutional symptoms; involve palliative care alongside disease-directed treatment.2,7

Monitor progression and treatment toxicity

  • Review counts, spleen, symptoms, response, infections, withdrawal risks and transformation to AML.1,2

Exam traps

  • A dry tap is not diagnostic alone.
  • MF can be primary or post-PV/post-ET.
  • JAK inhibitors improve symptoms/spleen but are not curative.
  • Do not stop a JAK inhibitor abruptly without specialist advice.

Illustrations

Tear-drop cells on a peripheral blood filmPeripheral blood smear showing numerous tear-drop red cells, or dacrocytes, a characteristic clue to marrow fibrosis in myelofibrosis.Paulo Henrique Orlandi Mourao, Wikimedia Commons · CC-BY-SA-3.0
Marrow fibrosis on trephine biopsyA bone marrow trephine with a reticulin stain showing dense fibrosis and clustered atypical megakaryocytes replacing normal marrow.Ed Uthman from Houston, TX, USA, Wikimedia Commons · CC-BY-2.0
Massive splenomegalyAn illustration or image of massive splenomegaly extending below the umbilicus from extramedullary haematopoiesis.Hellerhoff. Labeling by Mikael Häggström, Wikimedia Commons · CC-BY-SA-3.0

Key sources

  1. BSH: Diagnosis and evaluation of prognosis of myelofibrosis (Current UK BSH diagnosis and prognostic evaluation guidance for primary and secondary MF.)Published 6 Nov 2023
  2. BSH: The management of myelofibrosis (Current UK BSH management guideline for primary and secondary MF.)Published 1 Dec 2023 | Updated 22 Jul 2024
  3. NHS Salisbury: Myeloproliferative neoplasms (UK NHS overview of MPNs and specialist pathways.)
  4. NICE TA386: Ruxolitinib for myelofibrosis-related splenomegaly or symptoms (NICE recommendation for ruxolitinib in selected intermediate-2 or high-risk MF.)Published 23 Mar 2016
  5. NICE TA957: Momelotinib for myelofibrosis-related splenomegaly or symptoms (NICE recommendation for momelotinib in selected intermediate-2 or high-risk MF with moderate-to-severe anaemia.)Published 20 Mar 2024
  6. NICE TA1018: Fedratinib for myelofibrosis-related splenomegaly or symptoms (Current NICE appraisal for fedratinib in selected MF after ruxolitinib when momelotinib is unsuitable.)Published 20 Nov 2024
  7. BNF online (Check current antiplatelet, cytoreductive, JAK-inhibitor and supportive prescribing.)
  8. BSH: Updated guidelines for tumour lysis syndrome (Current UK tumour-lysis guidance.)Published 3 Sept 2025 | Updated 8 Dec 2025

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.