Platelets are blood cells that facilitate clotting. When platelet levels drop below the normal level of 150,000 per microliter, a person has thrombocytopenia. Platelets, the smallest blood cell, are actually cell fragments. Platelets clump together at the sight of injury to stop bleeding. Platelet levels drop for several reasons: platelet production may be low, or an increased number of platelets may be being destroyed in the bloodstream or the spleen.
Idiopathic Thrombocytic Purpura
Idiopathic thrombocytopenic purpura (ITP) is a low platelet count caused by antibodies that form and destroy platelets. ITP can be acute or chronic, with acute disease occurring more often in children, often after a viral infection. Acute thrombocytopenic purpura, which lasts less than six months, is more common than the chronic form, the National Heart Lung and Blood Institute states. Chronic thrombocytopenic purpura lasts 6 months to several years, occurs more often in adults, and is more common in women. ITP may also run in families. Steroids can help reverse ITP if an immune issue is causing the problem. Chronic ITP may require spleen removal, since the spleen makes the antibodies that destroy platelets.
If ITP complicates pregnancy, antibodies may cross the placenta and affect the fetal platelet count. Neonatal platelet count is less than 50,000 in 10 percent of babies whose moms have ITP, and may continue to drop after delivery, hematologist James George, M.D., of the University of Oklahoma Health Science Center stated.
Drug Induced Thrombocytopenia
Many drugs can cause thrombocytopenia, including sulfa drugs, quinine, heparin, non steroidal anti inflammatory (NSAID) drugs, penicillin, diuretics and oral hypoglycemics. Drug-induced thrombocytopenia can be immune or non-immune. Immune system disease produces antibodies that destroys platelets. Non-immune disease doesn't destroy platelets, but prevents bone marrow from making enough platelets.
Heparin causes a specific type of thrombocytopenia called heparin-induced thrombocytopenia, which starts 5 to 10 days after heparin therapy is started. Heparin is stopped immediately and another medication to decrease clots is started, oncologist and hematologist Stephen Szabo, M.D, reports on the Emory University School of Medicine website.
Gestational Thrombocytopenia
Thrombocytopenia affects 8 percent of pregnancies. Gestational thrombocytopenia is usually mild; the platelet count usually remains above 70,000, and usually resolves within 3 months of delivery. Thrombocytopenia develops in 15 percent of pregnancies complicated by preeclampsia, a condition characterized by hypertension, swelling of the face and hands, and protein in the urine; the cure for pre-eclampsia is delivery of the fetus.
Other Causes of Thrombocytopenia
Some diseases cause platelets to become trapped in an enlarged spleen, lowering the platelet count. This occurs in cirrhosis of the liver, which also decreases platelet production in the bone marrow. Aplastic anemia, chemotherapy medications and bone marrow cancer also decrease platelet production. Immune diseases that form antibodies to destroy platelets include connective tissue disorders such as systemic lupus erythematosis and a clotting disorder called disseminated intravascular coagulation, or DIC.
References
- FamilyDoctor.org; Idiopathic Thrombocytic Purpura
- Emory University School of Medicine: Evaluation of Thrombocytopenia; Stephan Szabo, M.D.
- Oklahoma University Health Science Center Thrombocytopenia in Pregnancy; James N. George, M.D.:
- National Heart, Lung and Blood Institute: Idiopathic Thrombocytic Purpura
