Two different in vitro growth patterns for erythroid precursors in 18 patients with pure erythrocytosis.

Growth patterns of marrow and blood erythroid progenitors were studied in 18 cases of pure erythrocytosis using different doses of erythropoietin. 8 cases demonstrated 'spontaneous' growth of CFU-E and blood BFU-E as observed in myeloproliferative disorders, but without an excess of circulating CFU-GM. 3 of these patients also had other symptoms of a pan-myelopathy. All these cases showed good sensitivity to 32P myelo-suppression. 10 cases demonstrated growth patterns of erythroid progenitors similar to those observed in normal subjects, except for an excess of blood BFU-E, which suggests an abnormality of homeostatic regulation. In 5 of these cases, myelo-suppression was not effective. It is suggested that a stem cell study could differentiate patients with pure erythrocytosis due to 'autonomous' abnormal stem cell growth from cases due to abnormal regulation factors, and that such a discrimination might be useful for the choice of therapy.