Phlebotomy is a valid option in adult patients with symptomatic hyperviscosity, but so far this has not been studied in patients with OHS.[118] Few papers shed light on the role of activated rennin-angiotensin system and the development of secondary erythropoiesis implicating a potential benefit of blocking the system with angiotensin converting enzyme inhibitor or angiotensin II receptor blockers leading to better management of polycythemia in these patients.[119, 120]. This evidence concerns the gene ACE and polycythemia.