While RCC is a recognized cause of erythrocytosis (4), there exists a possibility of RCC-associated erythrocytosis and concomitant PV: a literature review identified only a single case of concomitant RCC and myeloproliferative neoplasm identified as JAK2 V617F-positive essential thrombocythemia with an elevated platelet count, as opposed to an erythrocytosis (5). The gene discussed is JAK2; the disease is renal cell carcinoma.