Extramedullary hematopoiesis

Case contribution: Dr Radhiana Hassan


  • A 38 years old with underlying thalassemia major
  • Had 3 monthly blood transfusion
  • Baselin Hb=6.0 g/dL
  • On iron chelation therapy
  • Admitted for fever and sepsis
  • Diagnosed as dengue fever (positive IgM) and meliodosis
Chest radiograph in frontal view

Chest radiograph findings:

  • Expansion of anterior ribs at multiple levels and bilateral (yellow arrows)
  • Presence of lobulated mediastinal mass with clear outline (white arrows). No calcification within.
  • No lung lesion is seen.
  • No cardiomegaly. No pleural effusion.
CT scan lower thoracic region in axial plane; (A) soft tissue and (B) bone windows
CT scan of abdomen in coronal plane soft tissue and bone window post contrast

CT scan findings:

  • Generalised osteopenia with irregular trabecular pattern are seen.
  • Bony expansion ribs are also noted.
  • Lobulated well-defined paraspinal masses are seen.
  • Liver and spleen are enlarged.

Diagnosis: Extramedullary hematopoiesis


  • Hemopoiesis is the formation and maturation of blood elements which normally occurs in the marrow of long bones, the ribs, and the vertebrae in adults.
  • When the primary sites of hemopoiesis in the adult fails, various extramedullary sites take on the role of blood formation.
  • Extramedullary hemopoiesis favors certain sites such as the liver, the spleen, and the paraspinal regions of the thorax.
  • In the thorax, the most common imaging manifestations are paraspinal masses and rib expansion. Rib or diploic space expansion is not uncommon.
  • Cases of extramedullary hemopoiesis involving the pulmonary interstitium have been reported and have occasionally resulted in cardiopulmonary insufficiency.
  • Paraspinal hemopoietic tissues can extend into the central canal, especially in the thorax, and cause neurologic symptoms because of spinal cord compression.
  • Diffuse hepatosplenomegaly is also a common finding.
Author: radhianahassan