Erythroblast kinetics in pernicious anaemia, erythroleukaemia and sideroblastic anaemia.

DNA synthesis time (Ts) and 3H-thymidine labelling index (TLI) of erythroblasts have been determined in 25 patients with various types of haematologic disorders using in vitro double labelling method. No remarkable differences in both Ts and TLI were noted between haematologically normal subjects and patients with increased effective erythropoiesis (haemolytic anaemias), suggesting that the cell cycle time is not principally altered under the augmented erythropoiesis. In pernicious anaemia, Ts of basophilic erythroblasts was significantly shortened and TLI was elevated above normal. Normalization of erythropoiesis by vitamin B12 was associated with a transient increase of TLI in polychromatic erythroblasts, which was interpreted to reflect prevention of intramedullary premature death of basophilic megaloblasts. Erythroleukaemia showed a markedly prolonged Ts and lowered TLI indicating the presence of cells with prolonged cell cycle time. These findings contrasted to that of pernicious anaemia despite certain morphological as well as functional similarities. In idiopathic sideroblastic anaemia, prolongation of Ts was observed to a similar extent as erythroleukaemia, while TLI remained almost normal. In 2 cases with suspected erythroleukaemia presenting an intermediate clinical picture between erythroleukaemia and sideroblastic anaemia, Ts of basophilic erythroblasts was found to be prolonged along with modestly lowered TLI.