Erythropoietin-producing renal cyst and polycythemia vera. Clarification of their relationship

Described here is a patient with the splenomegaly, pancytosis and panhyperplastic marrow of polycythemia vera who was found to have bilateral renal cysts. Erythropoietin levels in the serum and in fluid from the cyst on the left kidney were elevated. After puncture, fluid aspiration and injection of a sclerosing solution into the cyst on the left kidney, the serum erythropoietin level became undetectable. Subsequent puncture of the cyst on the right kidney showed no erythropoietin activity in the cyst fluid. However, the patient's signs of polycythemia vera persisted. Specimens of the patient's marrow grown in vitro showed a lack of response to erythropoietin stimulation, characteristic of polycythemia vera. This case, with defined diagnostic criteria and erythropoietin levels before and after therapy, suggests that the association of renal cysts and pancytosis is coincidental, as opposed to the documented endocrinologic relationship between secondary erythrocytosis and erythropoietin-producing renal lesions. In eight cases of concomitant pancytosis and renal cysts, described in the literature, the question of a causal versus a coincidental relationship was raised but unanswered.