http___hr.265health.com_conditions-treatments_genetic-disorders_1016037271.html_1.xml
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causes Thalassemia is caused by mutations, or genetic errors, in genes that produce hemoglobin. These mutations result in reduced levels of hemoglobin, which is a protein in red blood cells that is responsible for carrying oxygen. The structure of hemoglobin is made up of four protein chains: two alpha hemoglobin (or alpha-globin) proteins and two beta hemoglobin (or beta-globin) proteins. Due to the reduced level of hemoglobin, there are fewer red blood cells circulating in the blood of individuals with thalassemia. Reduced numbers of red blood cells, also known as anemia, may be mild or severe. Thalassemia is an inherited disorder, meaning that it is passed on from a parent to a child. It is often inherited as an autosomal recessive trait, meaning that two copies of a mutated gene (one inherited from each parent) are needed to cause the disorder. However, some forms of thalassemia may be autosomal dominant, in which case only one copy of a mutated gene is needed to cause the disorder. A person who inherits a thalassemia gene or genes from one parent and normal genes from the other parent is called a carrier (thalassemia trait or thalassemia minor) and may pass the defective gene to offspring. Carriers typically have no signs and symptoms but may have mild anemia. If a person inherits more than one copy of the gene mutation, the disease is called thalassemia intermedia or thalassemia major. Patients are typically symptomatic with moderate to severe anemia. Beta thalassemia: Mutations that result in abnormally low levels of beta-hemoglobin cause a condition known as beta thalassemia. The HBB gene is responsible for making beta hemoglobin and a mutation that causes decreased production of beta hemoglobin results in beta thalassemia. A related condition, called sickle cell disease, results when mutations in the HBB gene cause defective rather than reduced levels of hemoglobin B. Beta thalassemia is classified based on the level of reduction in beta production. A reduction in beta hemoglobin leads to low levels of hemoglobin and may cause anemia depending on the severity. Mild forms of thalassemia are commonly called beta-plus thalassemia, while severe forms are often referred to as beta-zero-thalassemia. Beta-zero thalassemia is caused by the complete absence of beta protein production while beta-plus thalassemia is caused by a deficiency of beta protein production. People with beta thalassemia minor or beta thalassemia trait only carry one gene defect, are often asymptomatic, and have only mild anemia. When both gene defects are inherited, but only moderate anemia occurs, it is called beta thalassemia intermedia. If severe anemia occurs, then the disease is called beta thalassemia major. Severe beta thalassemia is also called Cooley's anemia. Beta defects are typically autosomal recessive, but in a small percentage of cases the HBB mutation follows an autosomal dominant pattern of inheritance. In a recessive disorder, if one parent is a carrier, there is a 50% chance with each birth that the child will also be a carrier and a 0% chance that the child will inherit the disease. If both parents are carriers, there is a 25% chance with each birth that the child will inherit the disease and a 50% chance that each child will be a carrier. Carriers typically have no signs and symptoms but some may have a mild form of anemia. If the disease is autosomal dominant and one parent has the disorder, there is a 50% risk that their child will have the disorder. If both parents have the disorder, there is a 75% chance that their child will have the disorder. Alpha thalassemia: Alpha thalassemia is an autosomal recessive disorder that affects the production of alpha hemoglobin. There are two genes responsible for the production of alpha hemoglobin: HBA1 and HBA2. Two of each of these genes are inherited from each parent, so each individual has a total of four genes that make up alpha hemoglobin. Alpha thalassemia occurs when one or more of these four genes is defective. The classification of alpha thalassemia depends on how many genes are defective and the severity of symptoms. When only one gene is defective, the person will have no sign of the alpha thalassemia. However, they can still pass the mutated gene to a child and are known as "silent carriers" of alpha thalassemia. Individuals who inherit two defective genes are said to have the alpha thalassemia trait (or alpha thalassemia minor). They are also considered carriers and may have mild anemia. Inheriting three genes results in hemoglobin H disease and is usually associated with moderate to severe anemia. If all four genes are defective, then this disorder is called alpha thalassemia major or hydrops fetalis. This is a very rare and serious disease that typically results in death shortly after birth. Delta thalassemia: Only about 3% of hemoglobin contains any delta chains, and thus a defect in the delta genes is negligible in terms of severity of effects. Often an individual with delta defects has normal blood cell counts. Even though there are no immediate physical consequences of delta thalassemia, the defect can interfere with the diagnosis of beta thalassemias, which can be severe. diagnosis Blood tests: Thalassemia can be diagnosed by a complete blood count (CBC) and hemoglobin (HB) studies. A CBC will determine the amounts of hemoglobin and red blood cells that are present. Carriers will have a normal hemoglobin level but may have a slightly reduced red blood cell count. People with more severe forms of thalassemia will have a lower level of red blood cells and hemoglobin. Hemoglobin studies can distinguish between the types and amount of circulating hemoglobin. The normal types of circulating hemoglobin are HB A, A2, and F. Any variation in the level of these hemoglobin types may indicate a diagnosis of thalassemia. A diagnosis can be made by distinguishing between the variations in the hemoglobin subtypes. Detection of beta thalassemia usually involves measuring the mean corpuscular volume (size of red blood cells). If the patient has beta thalassemia, the mean corpuscular volume will be slightly decreased. Hemoglobin tests will show an increased fraction of hemoglobin A2 (>2.5%) and a decreased fraction of hemoglobin A (<97.5%) for beta thalassemias. In patients with decreased red blood cell count (anemia), further tests need to be performed to determine if thalassemia is the cause of the anemia. To do this, iron levels can be drawn to rule out iron deficiency anemia. Genetic (DNA) testing: DNA tests may also be performed to confirm the presence of a mutated gene that may cause beta, alpha, or delta thalassemia. DNA tests are often used to confirm results from other tests, such as blood tests. Prenatal genetic testing: Thalassemia may be diagnosed prior to birth by analyzing blood samples taken from the fetus. Diagnosis of thalassemia in a developing fetus may also be done through amniocentesis, in which the amniotic fluid surrounding the unborn baby is sampled through a needle. Blood cells from the amniotic fluid may indicate thalassemia. Genetic tests may also be performed on blood or amniotic fluid. Because taking a blood sample may cause harm to a developing fetus, taking samples of amniotic fluid is generally preferred. It is important to note that any prenatal test carries a risk of miscarriage. Chorionic villus sampling (CVS): Chorionic villus sampling (CVS) is another type of prenatal diagnosis that can detect genetic problems in a fetus. Samples are taken from the chorionic villus or placental tissue. Any prenatal test carries a risk of miscarriage. Pre-implantation genetic diagnosis (PGD): A new procedure called pre-implantation genetic diagnosis (PGD) may be performed on embryos produced by in vitro (artificial) fertilization. This test allows parents to implant and carry only the embryos that do not carry the mutated genes that cause thalassemia. signs and symptoms Signs and symptoms may vary depending on the type and severity of thalassemia. Typically, symptoms that appear are caused by a decrease in circulating oxygen from anemia and low hemoglobin. Some common symptoms may include fatigue, shortness of breath, jaundice, and bone deformities in the face. Laboratory tests may reveal anemia and an enlarged spleen. Carriers of alpha thalassemia trait and beta thalassemia trait generally do not have symptoms. Alpha and beta thalassemia trait carriers may develop a mild form of anemia. The onset of thalassemia intermedia disorders may occur in early childhood or later in life. Symptoms are mild to moderate and may include poor and abnormal bone growth. Thalassemia major disorders usually appear early in childhood, which may be as early as two years of age. Symptoms may include poor appetite, slow growth, jaundice, delayed puberty, and enlarged liver, spleen, and heart. A symptom of life-threatening anemia is low oxygen circulation. A person that is born with alpha thalassemia major or hydrops fetalis usually dies before or shortly after birth. complications Mild forms of thalassemia do not shorten lifespan but severe thalassemia may lead to heart failure and death as early as 20 to 30 years of age. The use of transfusions and chelation therapy may improve the outcome. A successful bone marrow transplant will cure the disease. If thalassemia major goes untreated, there may be an increased susceptibility to infection. Heart failure and liver problems may also occur. Because there is not enough hemoglobin to bind the iron in the blood, there may be too much free iron in the blood. Therefore, iron toxicity may occur as a side effect of treatment. This can lead to heart, liver, and endocrine system damage. The concurrent use of deferasirox (Exjade®), an iron-chelating agent, may reduce the toxicity of iron therapy. A chelating agent binds to a specific substance and creates an inactive complex. Deferasirox binds to free iron and the complex it forms is then eliminated. This decreases free iron concentrations and reduces iron toxicity. risk factors It is estimated that 60 to 80 million people worldwide carry the beta thalassemia trait, and an estimated 1,000 cases of thalassemia exist in the United States. Beta thalassemia is considered to be a fairly common blood disorder that is thought to affect several thousand infants every year. Certain populations have a higher frequency of thalassemia. Beta thalassemia is more common among people of Mediterranean origin (Greek, Italian, Middle Eastern) and people of Asian and African descent. Alpha thalassemias mostly affect people of Southeast Asian, Indian, Chinese, or Filipino origin. Individuals with a family history of thalassemia have a higher risk of developing the disorder. Autosomal recessive inheritance: Thalassemia is caused by a mutation in a gene that contains the instructions for making hemoglobin. Most thalassemias are inherited as an autosomal recessive trait except in a very small percentage of beta thalassemia cases. Therefore, individuals who inherit two copies of this mutation (one from each parent) will develop thalassemia. Individuals who inherit only one copy of the mutation may not have symptoms of thalassemia but are known as "carriers" (thalassemia trait or thalassemia minor) because they can pass on the mutation to their children. If one parent carries the thalassemia trait, or only has one copy of the mutated gene, then each child will have a 50% chance of inheriting one mutated gene and also being a carrier. If both parents are carriers, each child has a 25% chance of inheriting two mutated genes, a 50% chance of inheriting only one mutation, and a 25% chance of inheriting neither of the mutations. Thus, if both parents are carriers, approximately one out of every four children will have a form of thalassemia. If one parent has thalassemia and the other parent does not carry the trait, then all of the children will be carriers. If one parent has thalassemia and the other parent is a carrier, then each child has a 50% chance of having thalassemia and a 50% chance of being a carrier. If both parents have thalassemia, then all of their children will also have thalassemia. Autosomal dominant inheritance: In a very small percentage of beta thalassemia cases, the disorder is inherited as an autosomal dominant trait. This means that just one copy of the mutated gene is needed for the disorder to occur. In other words, if one parent has beta thalassemia, there is a 50% chance that his/her child will have the disorder. If both parents have beta thalassemia, there is a 75% chance that the child will inherit the condition.
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najčešći uzrok thalassemia jedefekt u proizvodnji beta globinski ili alfa globinski . Beta globin čini pola hemoglobina , što je protein koji je u crvenim krvnim stanicama . Alpha bina čini drugu polovicu . Stoga su ti nedostaci se nazivaju beta talasemija ili alfa talasemija . Alpha Talasemija Alfa talasemija jebolest krvi rezultira teške anemije , a ponekad i smrt u fetus ili novorođeno dijete . Ozbiljnost bolesti strahovito varira ovisno o točnom gena inherited.An pojedinac s jedne abnormalnim alfa globinska kaže da ješutio nositelj alfa talasemija , koji se obično ne uzrokuje zdravstvene probleme u tom pojedincu , kao u pravilu ne postoji anemija prisutna . Osoba s dva abnormalne alpha bina gena ima alfa talasemija osobinu . To se često miješa s anemijom zbog manjka željeza , ali više željeza u prehrani ili željezom neće riješiti problem . Bolesnici s alfa talasemija potez uglavnom samo doživjeti blage anemije , a često ne pokazuju symptoms.However , kada je jedan roditelj ima alfa talasemija osobinu , adrugi roditelj ješutio prijevoznik , postoji25 % šanse da će njihovo dijete biti rođena s hemoglobina H bolesti , u kojima su tri ili četiri alfa bina geni su abnormalni . Hemoglobin H bolest može uzrokovati tešku anemiju , uvećanu slezenu i kosti deformities.If oba roditelja nose alfa talasemija osobinu , postoji25 % šanse da će njihovo dijete biti rođeno s alfa talasemija major,bolesti u kojoj sve četiri alfa globinsko geni su abnormalni . Većina djece rođene s alfa talasemija glavni umrijeti prije ili ubrzo nakon rođenja . Beta Talasemija Beta talasemija jedefekt u proizvodnji beta globinski . Beta talasemija je slična alfa talasemija na način da utječe na ljude i kako je prošli zajedno s djecom . Beta talasemija može uzrokovati anemiju u djece , i često zahtijeva česte transfuzije krvi u borbama . Djeca s beta talasemija često imaju koštane deformacije i iskustvo čestih lomova ili pukotina . Oni koji pate od beta talasemija ponekad mogu razviti bolesti srca zbog nereda . Srpastih stanica Anemija anemije srpastih stanica jebolest koja mutira crvene krvne stanice u srpom oblikovati da izgledaju kao kapital " C " Kada se krvne stanice srpom , to postaje vrlo teško za njih da se presele kroz krvne žile , a ponekad zapeti. Djeca čiji su roditelji oboje imaju srpastih stanica osobine imaju 25 % šanse da se naslijediti anemiju srpastih stanica . Anemija srpastih stanica može uzrokovati jaku bol , ozbiljne infekcije i oštećenja organa . Prosječni životni vijek osobama koje pate od bolesti je između 40 i 60 godina . Testiranje genetske bolesti genetičko testiranje u obliku krvi ili test sline često je ponudio perspektive roditelja koji su zabrinuti zbog prolaska genetske bolesti na svoju djecu . Genetičko testiranje ima svojih ograničenja , međutim . Pozitivan rezultat ne znači nužno ibolest će se prenijeti na djecu , ili da jepacijent će razviti bolest sebe . From:http://hr.265health.com/conditions-treatments/genetic-disorders/1016037271.html