Thrombotic Thrombocytopenic Purpura
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What is thrombotic thrombocytopenic purpura?Thrombotic thrombocytopenic purpura is a rare disorder that causes blood clots (thrombi) to form in small blood vessels throughout the body. These clots can cause serious medical problems if they block vessels and restrict blood flow to organs such as the brain, kidneys, and heart. Resulting complications include neurological problems (such as personality changes, headaches, confusion, and slurred speech), fever, abnormal kidney function, abdominal pain, and heart problems. In people with thrombotic thrombocytopenic purpura, clots in blood vessels are formed from clumps of platelets. Platelets are cell fragments that play a critical role in blood clotting. Because a large number of platelets are used to form clots in people with this disorder, fewer platelets are available to circulate in the bloodstream. A reduced level of circulating platelets is known as thrombocytopenia. Thrombocytopenia can lead to bleeding just under the surface of the skin, resulting in purplish spots called purpura. This disorder also causes red blood cells to break down (undergo hemolysis) prematurely. As blood squeezes past clots within blood vessels, red blood cells can break apart. A condition called hemolytic anemia occurs when red blood cells are destroyed faster than the body can replace them. This type of anemia leads to paleness, yellowing of the eyes and skin (jaundice), fatigue, shortness of breath, and a rapid heart rate. The two major forms of thrombotic thrombocytopenic purpura are an acquired (noninherited) form and a familial form. The acquired form usually appears in late childhood or adulthood. Affected individuals may have a single episode of signs and symptoms, or complications of the disorder may recur over time. The familial form of this disorder is much rarer and typically appears in infancy or early childhood. In people with the familial form, signs and symptoms often recur on a regular basis. How common is thrombotic thrombocytopenic purpura?The precise incidence of this condition is unknown, but researchers estimate that it affects 4 to 7 per million people each year in the United States. For unknown reasons, the disorder occurs more frequently in women than in men. The acquired form of thrombotic thrombocytopenic purpura is much more common than the familial form. What genes are related to thrombotic thrombocytopenic purpura?Mutations in the ADAMTS13 gene cause thrombotic thrombocytopenic purpura. The ADAMTS13 gene provides instructions for making an enzyme that is involved in the normal process of blood clotting. Both the familial form and the acquired form of thrombotic thrombocytopenic purpura result from a severe reduction in the activity of this enzyme. The familial form is caused by mutations in the ADAMTS13 gene that disrupt the enzyme's function. People with the acquired form do not have mutations in this gene; instead, their immune systems often produce specific proteins called antibodies that block the activity of the ADAMTS13 enzyme. A lack of ADAMTS13 enzyme activity disrupts the usual balance between bleeding and clotting. Normally, blood clots form at the site of an injury to seal off damaged blood vessels and prevent excess blood loss. In people with thrombotic thrombocytopenic purpura, clots form throughout the body as platelets bind together abnormally and stick to the walls of blood vessels. These clots can block small blood vessels unpredictably, causing organ damage and the other features of thrombotic thrombocytopenic purpura. Researchers believe that other genetic or environmental factors may contribute to the signs and symptoms of thrombotic thrombocytopenic purpura. In people with reduced ADAMTS13 enzyme activity, factors such as pregnancy, surgery, and infection may trigger abnormal blood clotting and its associated complications. How do people inherit thrombotic thrombocytopenic purpura?The familial form of thrombotic thrombocytopenic purpura is inherited in an autosomal recessive pattern, which means two copies of the gene in each cell are altered. Most often, the parents of an individual with an autosomal recessive disorder are carriers of one copy of the altered gene but do not show signs and symptoms of the disorder. The acquired form of thrombotic thrombocytopenic purpura is not inherited.
Source: National Institutes of Health
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Research from Nara Medical University reveals new findings on monoclonal antibodies
2007 AUG 20 -- New investigation results, "Plasma levels of ADAMTS13 antigen determined with an enzyme immunoassay using a neutralizing monoclonal antibody parallel ADAMTS13 activity LevEls," are detailed in a study published in International Journal of Hematology. According to a study from Kashihara, Japan, "Of plasma ADAMTS13 activity (ADAMTS13:AC) have been used for the diagnosis of patients with thrombotic thrombocytopenic purpura (TTP); however, the clinical usefulness of plasma ADAMTS13 antigen (ADAMTS13:AG) has been controversial, because antigen values vary widely among patients with acquired idiopathic TTP (ai-TTP).We have developed a novel enzyme-linked immunosorbent assay (ELISA) for the determination of plasma ADAMTS13:AG. This highly sensitive ELISA system using a neutralizing monoclonal antibody enables the detection of as little as 0.1% of the level in normal human plasma, corresponding to approximately 1 ng/mL purified plasma ADAMTS13." "The mean (±2 SD) plasma level of ADAMTS13:AG in healthy individuals was 106.4% ±39.3% (n=52). Patients with Upshaw-Schulman syndrome (USS) (n=20) and ai-TTP (n=30) showed significantly reduced ADAMTS13:AG levels (0.5% ±1.6% and 1.2% ±3.4%, respectively). The ADAMTS13:AG level was 48.4% ±42.6% in USS carriers (n=40) and <8.3% in ai-TTP patients with <0.5% ADAMTS13:AC. These values were almost parallel to those for ADAMTS13:AC. This ELISA may be useful for the rapid determination of ADAMTS13:AG," wrote H. Yagi and colleagues, Nara Medical University. The researchers concluded: "Further investigations of this antigen would be helpful in advancing the understanding of the pathogenesis of congenital and acquired TTP." Yagi and colleagues published their study in International Journal of Hematology (Plasma levels of ADAMTS13 antigen determined with an enzyme immunoassay using a neutralizing monoclonal antibody parallel ADAMTS13 activity LevEls. International Journal of Hematology, 2007;85(5):403-7). For more information, contact H. Yagi, Nara Medical University, Dept. of Blood Transfusion Medicine, Kashihara, Nara, Japan. Publisher contact information for the International Journal of Hematology is: Carden Jennings Publ Co. Ltd., Blake Center, Ste. 200, 1224 W Main St., Charlottesville, VA 22903, USA. Keywords: Japan, Kashihara, Monoclonal Antibodies, Biotechnology, Diagnosis, Diagnostics, Hematology, Medical Device, Monoclonal Antibody. This article was prepared by Hematology Week editors from staff and other reports. Copyright 2007, Hematology Week via NewsRx.com.
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