Erythrocytosis in patients with renal failure on hemodialysis: study of underlying mechanism by in vitro erythroid culture assay.

Five patients with erythrocytosis associated with renal failure on maintenance hemodialysis were investigated for in vitro erythroid progenitor growth and the effect of their uremic sera on normal erythropoiesis. The duration of hemodialysis prior to discovery of erythrocytosis ranged from 1 week to 96 months. None had acquired cystic disease and no other known cause of increased erythropoietin (Epo) production was identified. With the presence of Epo in cultures, all five patients grew erythroid colonies within normal or higher than normal ranges. Three patients formed spontaneous erythroid colonies in the absence of added Epo; all three fulfilled the clinical diagnosis of polycythemia vera (PV). The uremic sera from patients with PV lacked either a stimulating or an inhibiting effect on normal erythropoiesis. The association between renal failure and PV was coincidental. The other two patients without endogenous erythroid colony formation had enhanced erythropoietic activity in their sera, which increasingly stimulated the erythroid colony growth by normal bone marrow cells as the concentration of the uremic serum was increased. The etiology of increased Epo production in these 2 patients remained undefined during long-term follow-up. The present study on five uremic patients with polycythemia showed two different underlying mechanisms of erythrocytosis--characteristic autonomous erythroid proliferation for PV in three patients and inappropriate idiopathic Epo production in two patients.