Leiomyoma and erythrocytosis: a tumor producing a factor which increases erythropoietin production. Report of case.

E RYTHROCYTOSIS has been associated with various types of tumors.1 In some of these cases, the tumor was found to contain a substance which was similar to erythropoietin both immunochemically and in biologic activity. We shall here describe what we believe to be the first reported case of a patient with a leiomyoma of the esophagus and erythrocytosis. Experiments to determine the etiology of the erythrocytosis suggested that the tumor contained a substance that was not erythropoietin but had the ability to stimulate the production of erythropoietin by the kidneys.