Erythroid colony growth in congenital hypoplastic anemia.

Four children with congenital hypoplastic anemia (Diamond-Blackfan syndrome) and 30 control children with normal erythropoiesis were studied by a cell culture method in which human marrow, grown in a plasma clot, responds to added erythropoietin (EPO) with the appearance of discrete colonies of nucleated erythroid cells. The colonies arise from EPO-responsive stem cells and are not related to the number of morphologically identifiable marrow erythroids plated. Results of studies on control marrow indicated that without EPO there was little or no colony formation. Increasing EPO doses or nucleated marrow cells per culture resulted in a linear increase in colony numbers. The optimal EPO concentration of 2.5 U/ml yielded a mean of 158 +/- 79 colonies/1 x 10(5) nucleated cells on day 7 of incubation. Even in the absence of recognizable erythroids, marrows of all four patients with anemia grew erythroid colonies. Two patients on no therapy had decreased colony numbers. The other two, on prednisone, had normal numbers. Sera from patients did not inhibit colony formation from either autologous or control marrow. In contrast, serum from an adult with acquired pure red cell aplasia produced striking inhibition of colony growth. It appears that the red cell failure in this disorder is not due to an absence of erythroid stem cells, and a serum inhibitor to erythropoiesis as seen in the acquired disease is unlikely.