Originating in the bone marrow, platelets play an important role in blood clotting. Normal platelet counts range between 150,000 and 400,000/mm3. Thrombocytopenia means the count falls lower than this and thrombocytosis means the platelet count exceeds the limit. An overabundance of platelets causes them to aggregate or stick together and raises the possibility of forming a clot. The traveling blood clot can cause strokes, heart attacks and loss of limb by blocking blood flow. According to "Mosby's Diagnostic and Laboratory Test Reference, 5th ed.," the causes of thrombocytosis remain unknown in some cases, while in other cases it results from an illness. Still other reports of elevated platelet counts do not indicate thrombocytosis but rather occur because of interfering factors.
Unknown Causes
The label "essential thrombocytosis" means a high platelet count but not in relation to or as a result of a separate illness. When thrombocytosis comes from another illness, treating the underlying illness corrects the platelet overproduction. However, thrombocytosis that comes with no influencing factors receives a different treatment approach and can come from genetic origins. The drug of choice, hydroxyurea, prevents the high volume of platelets from clotting the blood unnecessarily. A person who suffers from chronic essential thrombocytosis may need aspirin therapy for life.
Illness
"Reactive thrombocytosis" occurs in response to illness. For example, iron deficiency anemia raises the platelet count. In addition, with surgical removal of the spleen, the platelet count rises as a part of a condition called postsplenectomy syndrome. Another blood illness, polycythemia vera, has a characteristic increase in red blood cells but the platelets increase as well. Malignancy, including solid tumors, leukemia and lymphoma, leads the list of the most common cause of sudden onset thrombocytosis. Inflammatory disorders like rheumatoid arthritis and ulcerative colitis cause a platelet increase, as do other chronic illnesses such as renal failure, cirrhosis of the liver and chronic pancreatitis.
Other Causes
Certain circumstances influence the results of the test that measures platelets. Living at high altitudes will cause an increase. Strenuous exercise contributes to an elevated count. Also, medications can affect the outcome of the test. Some oral contraceptives increase the body's platelets, while other drugs cause a decrease. According to "Hematology/Oncology Secrets, 2nd ed.," some peoples' platelets clump together and cause an inaccurate count. Automated counting, used by most modern labs, carries a 10 percent to 15 percent margin of error in the platelet count test. Therefore, in the absence of symptoms, an elevated platelet count needs re-evaluation before a treatment plan can goes into effect.
References
- "Hematology/Oncology Secrets, 2nd ed;" Marie E. Wood, MD; 1999
- "Mosby's Diagnostic and Laboratory Test Reference, 5th ed.;" Kathleen Deska Pagana, PhD, RN and Timothy James Pagana, MD, FACS; 2001
