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