Elevated red cell adenosine deaminase activity: a marker of disordered erythropoiesis in Diamond‐Blackfan anaemia and other haematologic diseases

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Abstract
Red-cell adenosine deaminase (ADA) activity in children with Diamond-Blackfan anaemia is significantly increased (1·91±0·90 U/g Hb) compared to that seen in transient erythroblastopenia of childhood (0·80±0·16 U/g Hb) or normal individuals (0·61±0·13 U/g). These data thus further support that measurement of this purine metabolic enzyme is useful in diagnosing the cause of pure RBC aplasia in children. Of interest, however, elevated RBC-ADA activity also is seen in some children with acute leukaemia and other haematologic disorders. In children with acute lymphoblastic leukaemia (ALL), the increase in RBC-ADA activity is proportional to the degree of anaemia. However, the elevated RBC-ADA activity in this leukaemic population is not related to the fetal haemoglobin concentration. These data suggest increased RBC-ADA activity may be a non-specific manifestation of abnormal erythroid stem cell function, an alteration distinct from that seen with reactivation of fetal erythropoiesis. However, since almost all patients with Diamond-Blackfan anaemia manifest elevated RBC-ADA activity, this chemical alteration yet may reflect the specific erythroid differentiation lesion in this disorder.