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Extramedullary Hematopoiesis in Thalassemia



General Considerations

  • Response to insufficient blood cell production by production of blood elements outside of the marrow cavity
  • Most often due to hemolytic anemias such as sickle cell anemia, thalassemia and hereditary spherocytosis
  • May also be seen in prolonged iron deficiency anemia, myelofibrosis and sclerosis, polycythemia, leukemia and lymphoma
  • About a quarter of patients have no known hematologic disease
  • Areas of extramedullary hematopoiesis include the spleen, paraspinal regions of the thorax, liver and sometimes adrenals, bowel, dura mater and breast
  • Thalassemia is an inherited autosomal recessive blood dyscrasia resulting in underproduction of globins which may lead to severe anemia

Clinical Findings

  • Most often microscopic and asymptomatic
  • Chronic anemia

Imaging Findings

  • Bilateral paraspinal masses with round,  lobulated margins
  • Thoracic masses occur most often in patients with thalassemia or congenital hemolytic anemia
  • Medullary expansion of the bony structures with widening of the ribs being the most pronounced bony finding
  • Resorption of trabeculae produces coarsened appearance to bones
  • Splenomegaly (or absent spleen)
  • Masses to don’t calcify and do not usually cause bone erosion
  • The lesions are usually of low-attenuation on non-contrast CT and may mildly enhance after contrast

Differential Diagnosis

  • Neurofibromatosis

Treatment

  • Blood transfusions
  • Hydroxyurea reported to decrease the size of the masses

Complications

  • Spinal cord compression
  • Pleural effusions
  • Hemothorax
  • Respiratory failure

Extramedullary Hematopoiesis in Thalassemia. Left: There are large paraspinal masses (white arrows) with smoothly marginated, lobulated contours. All of the ribs (red arrow) are expanded and the overall bone density is increased. Right: large paraspinal masses are seen (white arrows).
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Extramedullary Hematopoiesis: Breathtaking and Hair-Raising. N Engl J Med 1999; 341:1702-1704

 

Extramedullary hematopoiesis (EMH). Rita Agarwala, MD. Applied radiology, April, 2006.