Acquired aplastic anemia

Acquired aplastic anemia (AA) is characterized by low peripheral blood counts and decreased bone marrow cellularity. The cause of AA is unknown in the majority of cases, hence the term idiopathic aplastic anemia. The major pathophysiologic mechanism implicated in acquired AA is autoimmune dysregulation resulting in damage to hematopoietic stem and progenitor cells. Hematopoietic stem cell transplantation (HSCT) from a human leukocyte antigen matched family donor provides the best chance of cure with overall survival rates above 90% at 5–10 years post-transplant with few late effects. Immunosuppressive therapy (IST) targeting dysregulated T cells is considered the next best therapeutic option when a family donor is not available. Unrelated donor HSCT is slowly emerging as superior to IST when the procedure can be applied shortly after diagnosis, due to improvements in HSCT donor matching and supportive care. Advances in gene discovery and genetic diagnostic techniques have shown that as many as 20–30% of patients previously thought to have idiopathic AA actually have an underlying genetic cause, making it clear that extending genetic testing beyond basic screening is of paramount importance.