Exceptionally high serum erythropoietin activity in an anephric patient with severe anemia

An exceptionally high serum erythropoietin (EPO) activity was documented in an anephric patient with severe anemia who required transfusions every 4 weeks. The patient's serum EPO was comparable to normal human urinary EPO in the polycythemic mouse assay and was neutralized by an antiserum against EPO. The patient's serum inhibited EPO stimulated-heme synthesis by normal human marrow cells in vitro. This finding suggests that an inhibitor played an important role in causing the anemia of this uremic patient.