Aplastic anemia

Last revised by Daniel J Bell on 12 Dec 2022

Aplastic anemia is a rare hematopoietic stem-cell disorder. The condition results in pancytopenia and hypocellular bone marrow. Most cases are acquired, however, there are unusual inherited forms.

Aplastic anemia manifests as a marked reduction in the number of pluripotent hematopoietic stem cells. It is immune-mediated in most cases where autoreactive lymphocytes mediate the destruction of hematopoietic stem cells. Environmental exposures (e.g. drugs, viruses, and toxins) are thought to initiate the aberrant immune response in some patients, but most cases are classified as idiopathic.

Signal characteristics follow differences in fatty versus hematopoietic marrow.  Reported patterns include 3:

  • focal low-signal (both TI and T2) areas (likely representing islands of active hematopoietic cells) interspersed with high-SI areas in the marrow of the spine. Note this pattern is also seen in lymphoma, metastases and myeloma.

  • diffuse high-signal marrow without focal abnormalities in the pelvis and proximal femoral regions

MRI is also useful for assessment of response to treatment in aplastic anemia as well as other hematopoietic disorders 4.

Similar to other autoimmune diseases, aplastic anemia has a varied clinical course which ranges from some patients having mild symptoms that necessitate little or no therapy to others presenting with life-threatening pancytopenia. Acquired aplastic anemia can be effectively treated by allogeneic bone-marrow transplantation, immunosuppression (generally anti-thymocyte globulin and cyclosporine), and high-dose cyclophosphamide.

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