To study the action of corticosteroids on erythroid precursors,(burst forming unit-erythroid and colony forming unit-erythroid) in Diamond-Blackfan Syndrome (DBS), marrow from a newly diagnosed untreated infant was studied in vitro with prednisone and dexamethasone. This patient subsequently proved to be steroid responsive. Colony numbers increased linearly in an erythropoietin (EPO) dose response study. There was marked enhancement of colony numbers at all EPO doses after adding either prednisone (10-6 M) or dexamethasone (10-9 M) to the cultures. The data indicate that corticosteroids augment erythropoiesis at both early (BFU-E) and late (CFU-E) stages of development in DBS. In contrast, marrow from a second infant with DBS, clinically steroid resistant, failed to respond to steroids in vitro.

Speculation: It seems reasonable that in some patients with Diamond-Blackfan syndrome, erythroid precursors have a relative insensitivity to erythropoietin (EPO). Corticosteroids appear able to modify EPO receptor sites on the progenitor cell membrane in vitro, thus increasing EPO sensitivity and partially correcting the erythropoietic defect.