Definition of Thrombocytopenia
Thrombocytopenia is a condition in which there is a deficient number of circulating platelets.
Description of Thrombocytopenia
Thrombocytopenia may be congenital or acquired.
The acquired form is more common, especially among elderly. In either case, it usually results from decreased or defective production of platelets in the bone marrow (for example, in leukemia, aplastic anemiaand with toxicity from certain drugs), increased destruction outside the marrow caused by an underlying disorder (such as cirrhosis of the liver, disseminated intravascular coagulation and severe infection) or dilution of platelets.
Less commonly, thrombocytopenia results from increased sequestration of platelets in the spleen.
Causes and Risk Factors of Thrombocytopenia
Acquired thrombocytopenia may result from the use of certain drugs, such as quinine, quinidine, rifampin, heparin, nonsteroidal anti-inflammatory agents, histamine blockers, most chemotherapeutic agents, allopurinol and alcohol.
Impaired production of platelets usually occurs when stem cells are injured or prevent their proliferation in bone marrow. Thrombocytopenia may be accompanied by varying degrees ofanemia (low red blood cells) and leukopenia (low white blood cells). Diagnosis of a platelet production defect is established by examination of a bone marrow aspirate or biopsy.
The most common causes of decreased platelet production are marrow aplasia (when the marrow is not developing naturally), fibrosis (an abnormal formation) or infiltration with malignant cells.
Since one-third of the platelet mass is normally sequestered in the spleen, a splenectomy may increase the platelet count by 30 percent. In contrast, when the spleen enlarges, the fraction of sequestered platelets increases, lowering the platelet count. The most common causes of splenomegaly (enlarged spleen) are portal hypertension secondary to liver disease and splenic infiltration with tumor cells, or with...