Platelets, or thrombocytes, are described as “small, irregularly-shaped anuclear cells (i.e. cells that do not have a nucleus containing DNA), 2-3 µm in diameter which are derived from fragmentation of precursor megakaryocytes”; megakaryocytes are bone marrow cells and the platelets are able to enter the bloodstream through broken megakaryocytes caused by thrombopoietin (hormone that maintains the platelet count).
Platelets, red cells and plasma largely make up the composition of human and animal blood. They are microscopic cells that usually survive in the body for 8 to 12 days; they play a significant role in hemostasis and coagulation of the blood. Coagulation prevents further damage to impaired blood vessels.
Healthy persons will have a normal platelet count of 150, 000 to 450,000 platelets per microliter (x 10–6/Liter) of blood. Platelet levels that are below 20,000 per microliter may result in spontaneous bleeding. High platelet counts known as thrombocytosis may result in health conditions such as a stroke, as excess coagulation will create abnormal blood clots. Abnormally low platelet counts may cause extensive bleeding and lead to death. A platelet count is a test used to measure how many platelets are present in the blood. A blood sample is drawn from a vein in the arm or for babies, the finger or foot heel is pricked. The test is usually administered in persons that have mysterious bruises to the skin or a wound with abnormal bleeding.
Causes of Low Platelets
Aplastic anemia is a rare form of blood disorder where the body’s production of new blood cells is reduced. This may happen if the blood stem cells become damaged and the body is unable to effectively replace the damaged ones. The overall result is a low count in the red or white blood cells and platelets. Aplastic anemia causes fatigue, uncontrolled bleeding and high infection risks.
Proteins that are present in the blood (antibodies) may cause platelets to join together. The antibodies may also bind to a chemical in the blood during lab testing. Both situations may give a false platelet count.
Diseases that are inherited may contribute to low platelet counts. May Hegglin anomaly is a rare blood disorder where there are abnormalities in some blood components including the platelets. Persons may develop bleeding problems with this disorder. Bernard Soulier syndrome is a severe bleeding disorder that causes excessive and continuous bleeding, low platelets and large platelets. Bernard-Soulier platelets are missing a part of the platelet that is involved in the initial steps of coagulation.
Defective Platelet Production
Platelets in the bone marrow may be flawed from abnormalities in the cells. This will result in lower megakaryocytes and lower platelet production. Abnormal bone marrow cells can be caused by acute leukemia and cancer cells. Impaired platelet production can also result in low platelet counts. Risk factors of this include viral agents, side-effects from anti-cancer agents and vitamin deficiencies.
Burn victims, persons requiring new organs or marrow transplant, and those who have undergone heart surgery will often suffer from low platelet counts because of their complications. Low platelet count may also the caused from a condition known as splenic sequestration (blood pooling in the spleen).