• The first type of red cell aplasia is congenital hypoplastic anemia, also known as Diamond-Blackfan anemia (DBA). This is a life-long condition often requiring specific drug therapy, red cell transfusions, and in some cases bone marrow transplantation. The erythrocytes in DBA patients have several unusual features. One of the most interesting abnormalities has been an elevated level of adenosine deaminase (ADA) activity, seen in 75% of affected patients.

• The second type of red cell aplasia is due to a brief immunologic suppression of normal erythropoiesis occurring in otherwise healthy children. This transient erythroblastopenia of childhood (TEC) remits within weeks to a few months of onset. ADA activity is almost always normal.

The relationship of this enzyme alteration to the pathophysiology of RBC aplasia is not known, although it remains a useful marker in diagnosing many children with DBA.