Rabu, 01 Januari 2014
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Thalassemia Treatment
Thalassemia Treatment
Thalassemia Treatment : Patients with beta thalassemiarequire regular transfusions of red blood cells. These transfusions alleviate the symptoms of anemia and suppress the production of a patient’s own defective red cells, allowing bone marrow to return to normal size and bones to return to their normal shape.
However, transfusion regimens interrupt the body’s normal recycling of iron, a crucial component of the hemoglobin molecule. The body is unable to excrete iron, and with each transfusion of red cells, iron gradually accumulates in the body, with damaging results. If untreated, the toxic buildup of iron leads to death usually from heart failure in a patient’s late teens.
To prevent the fatal accumulation of iron, patients are treated with iron chelators, medications that bind iron and allow it to be excreted from the body. The most widely used iron chelator is deferoxamine, which is delivered through a needle placed under the skin and attached to a small pump that the patient wears for 8 to 12 hours each day. Many patients find this intensive treatment regimen difficult to maintain, and some do not wear the pump long enough to eliminate all of the excess iron from their body. Despite these difficulties, life expectancy for patients with thalassemia has steadily increased over the last several decades. With transfusion and chelation regimens, 90 percent of patients survive at least to age 25.
Currently the only way to cure thalassemia is by transplantation of stem cells, the cells in bone marrow that are responsible for blood cell formation. In this procedure, the bone marrow is destroyed with large doses of radiation or chemotherapy; then the patient’s defective stem cells are replaced with normal stem cells from an immunologically compatible donor, usually a sibling. Unfortunately, stem cell transplantation can help only a minority of thalassemia patients. Fewer than 25 percent of patients have a compatible sibling who could donate stem cells. Further, even if a compatible donor is available, anemia and other complications of thalassemia make some patients too sick to undergo transplantation. The transplant procedure itself can result in severe complications or even death.
In recent years, the search for new treatments to help thalassemia patients has focused on fetal hemoglobin, the predominant form of hemoglobin produced before birth. Fetal hemoglobin is made up of amino acids with two alpha chains and two gamma chains. Shortly before birth, the gene that produces the gamma chain is turned off, and the gene that produces the beta chain is turned on. Most patients with beta thalassemia have normal gamma genes and can produce normal fetal hemoglobin. In fact, scientists have long known that patients with beta thalassemiawho also continue to produce fetal hemoglobin after birth have milder disease. For this reason, scientists are working to develop treatments that would turn a patient’s gamma genes back on again. The resulting increase in fetal hemoglobin in the blood would work just like a blood transfusion relieving the symptoms of anemia and allowing bones to return to their proper shape without transfusion’s negative side effects.
However, transfusion regimens interrupt the body’s normal recycling of iron, a crucial component of the hemoglobin molecule. The body is unable to excrete iron, and with each transfusion of red cells, iron gradually accumulates in the body, with damaging results. If untreated, the toxic buildup of iron leads to death usually from heart failure in a patient’s late teens.
To prevent the fatal accumulation of iron, patients are treated with iron chelators, medications that bind iron and allow it to be excreted from the body. The most widely used iron chelator is deferoxamine, which is delivered through a needle placed under the skin and attached to a small pump that the patient wears for 8 to 12 hours each day. Many patients find this intensive treatment regimen difficult to maintain, and some do not wear the pump long enough to eliminate all of the excess iron from their body. Despite these difficulties, life expectancy for patients with thalassemia has steadily increased over the last several decades. With transfusion and chelation regimens, 90 percent of patients survive at least to age 25.
Currently the only way to cure thalassemia is by transplantation of stem cells, the cells in bone marrow that are responsible for blood cell formation. In this procedure, the bone marrow is destroyed with large doses of radiation or chemotherapy; then the patient’s defective stem cells are replaced with normal stem cells from an immunologically compatible donor, usually a sibling. Unfortunately, stem cell transplantation can help only a minority of thalassemia patients. Fewer than 25 percent of patients have a compatible sibling who could donate stem cells. Further, even if a compatible donor is available, anemia and other complications of thalassemia make some patients too sick to undergo transplantation. The transplant procedure itself can result in severe complications or even death.
In recent years, the search for new treatments to help thalassemia patients has focused on fetal hemoglobin, the predominant form of hemoglobin produced before birth. Fetal hemoglobin is made up of amino acids with two alpha chains and two gamma chains. Shortly before birth, the gene that produces the gamma chain is turned off, and the gene that produces the beta chain is turned on. Most patients with beta thalassemia have normal gamma genes and can produce normal fetal hemoglobin. In fact, scientists have long known that patients with beta thalassemiawho also continue to produce fetal hemoglobin after birth have milder disease. For this reason, scientists are working to develop treatments that would turn a patient’s gamma genes back on again. The resulting increase in fetal hemoglobin in the blood would work just like a blood transfusion relieving the symptoms of anemia and allowing bones to return to their proper shape without transfusion’s negative side effects.
(source)
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