Aplastic anemia

Aplastic anaemia is a rare haemopoietic stem-cell disorder. The condition results in pancytopaenia and hypocellular bone marrow. 

Most cases are acquired, however there are unusual inherited forms.

Pathophysiology

Aplastic anaemia is manifests as a marked reduction in the number of pluripotent haematopoietic stem cells. It is immune mediated in most cases where autoreactive lymphocytes mediate the destruction of haemopoietic 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.

Radiographic features

MRI

Signal characteristics follow differnences in fatty versus haematopoetic marrow.  Reported patterns include ³

• focal low-signal (both TI and T2) areas (likely repreresting islands of active haematopeotic 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 pelvis and proximal femoral regions

Complications

• development of  paroxysmal nocturnal haemoglobinuria (PNH)
• development of myelodysplastic syndrome

Treatment and prognosis

Similarly to other autoimmune diseases, aplastic anaemia 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 anaemia can be effectively treated by allogeneic bone-marrow transplantation, immunosuppression (generally antithymocyte globulin and cyclosporin), and high-dose cyclophosphamide.