living in the Middle East. Other causes of reactive thrombocythemia include: post surgery, iron deficiency, drugs, and rebound effect after bone marrow suppression. The SARS disease caused thrombocytosis. Once the reactive causes of thrombocythemia are ruled out, clonal thrombocythemia should be considered. The most common cause of clonal thrombocythemia is a myeloproliferative neoplasm. These include: essential thrombocythemia, chronic myelogenous leukemia, polycythemia vera, and primary myelofibrosis. Extremely rare causes of thrombocythemia are spurious causes. This is due to the presence of structures resembling platelets in the blood such as needle-like cryoglobulin crystals, cytoplasmic fragments of circulating leukemic cells, bacteria, and red blood cell microvesicles. These structures are counted as platelets by the automated machine counter; therefore, causing the platelet number to be falsely elevated. However, such error can be avoided by doing a peripheral blood smear. Diagnosis Laboratory tests might include: full blood count, liver enzymes, renal function and erythrocyte sedimentation rate. If the cause for the high platelet count remains unclear, bone marrow biopsy is often undertaken, to differentiate whether the high platelet count is reactive or essential. Treatment Often, no treatment is required or necessary for reactive thrombocytosis. In cases of reactive thrombocytosis of more than 1,000x109/L, it may be considered to administer daily low dose aspirin (such as 65 mg) to minimize the risk of stroke or thrombosis. However, in essential thrombocythemia where platelet counts are over 750x109/L or 1,000x109/L, especially if there are other risk factors for thrombosis, treatment may be needed. Selective use of aspirin at low doses is thought to be protective. Extremely high platelet counts can be treated with hydroxyurea (a cytoreducing agent) or anagrelide (Agrylin). In Janus kinase 2 positive disorders, ruxolitinib (Jakafi) can be effective. References Further reading External links Coagulopathies