Complications Perhaps no other condition in clinical medicine has caused otherwise astute physicians to intervene inappropriately more often than thrombocytosis, particularly if the platelet count is 1 x 106/µL. It is commonly believed that a high platelet count causes intravascular stasis and thrombosis; however, no controlled clinical study has ever established this association, and in patients younger than age 60, the incidence of thrombosis was not greater in patients with thrombocytosis than in age-matched controls. To the contrary, very high platelet counts are associated primarily with hemorrhage due to acquired von Willebrand disease. This is not meant to imply that an. | Chapter 103. Polycythemia Vera and Other Myeloproliferative Diseases Part 10 Complications Perhaps no other condition in clinical medicine has caused otherwise astute physicians to intervene inappropriately more often than thrombocytosis particularly if the platelet count is 1 x 106 uf. It is commonly believed that a high platelet count causes intravascular stasis and thrombosis however no controlled clinical study has ever established this association and in patients younger than age 60 the incidence of thrombosis was not greater in patients with thrombocytosis than in age-matched controls. To the contrary very high platelet counts are associated primarily with hemorrhage due to acquired von Willebrand disease. This is not meant to imply that an elevated platelet count cannot cause symptoms in a patient with ET but rather that the focus should be on the patient not the platelet count. For example some of the most dramatic neurologic problems in ET are migraine-related and respond only to lowering of the platelet count while other symptoms such as erythromelalgia respond simply to platelet cyclooxygenase 1 inhibitors such as aspirin or ibuprofen without a reduction in platelet number. Still others may represent an interaction between an atherosclerotic vascular system and a high platelet count and others may have no relationship to the platelet count whatsoever. Recognition that PV can present with thrombocytosis as well as the discovery of previously unrecognized causes of hypercoagulability Chap. 111 make the older literature on the complications of thrombocytosis unreliable. Essential Thrombocytosis Treatment Survival of patients with ET is not different than for the general population. An elevated platelet count in an asymptomatic patient without cardiovascular risk factors requires no therapy. Indeed before any therapy is initiated in a patient with thrombocytosis the cause of symptoms must be clearly identified as due to the elevated platelet count. When the
