Primary myelofibrosis

  • 1.5 per 100000, M=F, 50-60 years
  • Myeloproliferative neoplasm of unknown etiology
  • Clonal proliferation of hematopoietic stem cells
  • Progressive bone marrow fibrosis leads to anemia, splenomegaly and extramedullary hematopoiesis
  • JAK2 genetic abnormality in 55% cases
  • Pancytopenia with abnormal red cell morphology
  • Weakness, dyspnea, weight loss
  • Increased risk of infection and gout
  • Sites of extramedullary hematopoiesis: liver, spleen, lymph nodes, lung, choroid plexus, kidney
  • Death in 2-3 years if allogenic stem cell transplant is not done. Leukemia may also develop
  • Bone sclerosis – diffuse, patchy, mainly in axial skeleton and in major long bone metaphyses
  • Sclerosis – due to trabecular and endosteal new bone formation, this reduces marrow diameter
  • Lucent areas in bone due to fibrous tissue
  • Periosteal reaction – 1/3 of cases – at medial aspect of distal femur and proximal tibia
  • Mixed sclerotic and lytic pattern – ‘superscan’ appearance
  • MRI shows synovium infiltration by bone marrow elements
  • Leukemic conversion shows extraosseous soft tissue mass
  • Extramedullary hematopoiesis – hepatosplenomegaly, bilateral paravertebral masses in thorax, enlargement of ribs, pre-sacral mass. Fat containing non calcifying lesions. Fat signal suggests inactivity. Enhancement suggests activity
Read more

Guermazi, A., et al. “Imaging findings in patients with myelofibrosis.” European radiology 9.7 (1999): 1366-1375.