SERUM ERYTHROPOIETIN CONCENTRATIONS IN PATIENTS WITH MYELODYSPLASTIC SYNDROMES

Medullary dyserythropoiesis with reduced production of erythrocytes is an early and consistent feature of myelodysplastic syndromes (MDS). The mechanism underlying the disturbed red cell proliferation and maturation is presently unknown. In order to study the role of erythropoietic growth factors, we determined by radioimmunoassay the serum concentrations of immunoreactive erythropoietin (Epo) in 42 non-transfused patients with primary and secondary MDS. Their median hemoglobin concentration at the time of Epo measurement was 9.1 g/dl (range, 5.7-14.6). Compared with the control group, 83% of the MDS patients had increased serum Epo levels, ranging from 26-4530 mU/ml. Although in the entire patient population an inverse relationship between serum Epo and hemoglobin concentrations was noted (r = -0.35; p = 0.02), Epo titers differed markedly between patients at comparable degrees of anemia. In 7 patients presenting with a hemoglobin concentration between 5.9 and 11.9 g/dl, excessive elevations of Epo levels (> 500 mU/ml) were found. In contrast to previous observations, serum Epo concentrations were not shown to correlate with the percentage of erythroblasts in the bone marrow. There was, however, a significant relationship between the Epo activity and the degree of medullary dyserythropoiesis, as assessed by morphological criteria (p < 0.01). From these data we conclude that the anemia in MDS is not due to an endogenous Epo deficiency. The marked variability of Epo production in these disorders is not fully explained by the degree of anemia, but may also reflect inherent abnormalities of the myelodysplastic erythropoiesis.