Comparison with various deletion forms of alphathalassemia suggests that, in terms of intracellular globin chain precipitates and free betachain pool, homozygous hbcs red. Alpha thalassemia is a type of thalassemia that is inherited passed down through families. Several patients have been cured with bone marrow transplants after birth. Deletion testing wont find all of the mutations that cause alphathalassemia. The primary defect is the reduced or absent production of the alpha globin chains, which constitute the moieties of. This means you can pass on only one of these pairs, so your child can receive only one alpha deletion from you. Alphathalassaemia is more frequently caused by deletion than single point mutations or nucleotide insertions and deletions involving the canonical sequences controlling gene expression. Alphathalassemia types, causes, diagnosis, treatment. The more severe forms of alphathalassemia are found in southeast asians glader and look, 1996 and less commonly in infants of mediterranean origin, and are rare in africans. Alpha thalassemia causes and tratment options jgh delhi. Feel free to comment and suggest what you would like to see in the future, and i will do my best to fulfill those. Alpha thalassemia hba1 and hba2 7 deletions arup lab. Alphathalassemia is caused most frequently by deletions involving one or both.
This will help assess whether a fetus could be at risk for alphathalassemia major or hemoglobin h disease, if the partner is also an alphathalassemia carrier. Higher incidence in people of asian descent when compared with the general population. There are at least 4 different and distinct alphathalassemias. Thalassemia is a type of thalassemia that is caused by a deficiency of the alpha globin protein. Thalassemia is caused by deletion in approximately 95% of cases, with the remaining minority due to point mutations figure 1. Alpha thalassemia majornew mutations, intrauterine. The severity of alpha thalassemia depends on the number of defective. Alpha thalassemia genetics question made simple youtube. This means your child has a one or twoalpha gene deletion and has alpha thalassemia trait or is a silent carrier. One gene is missing or damaged, and the other 3 are normal. At conception, each sib of an individual with hb bart syndrome has a 25% chance of having hb bart syndrome, a 50% chance of having.
Hemoglobin is the protein in red blood cells that carries oxygen to cells throughout the body. It causes the body to make less hemoglobin than normal. The present study aimed to determine the effect of. Alpha thalassemia carrier two alpha chain genes are deleted, either. Homozygous means that this same deletion occurs on both clusters. Alphathalassemia is one of the two forms of the life threatening blood disease known as thalassemia. And alpha thalassemia is caused by mutations in the alpha genes, most commonly a gene deletion. I repeat the alpha thalassemia test and the result was. This condition causes mild to severe anemia, based on the type of alpha thalassemia that is inherited. Molecular analysis of a large novel deletion causing.
Alpha thalassemia deletionduplication and constant spring. This causes a shortage of red blood cells and low levels of oxygen in the bloodstream, leading to a variety of health problems. Silent carrier, alpha thalassemia trait, hemoglobin h disease, hemoglobin hconstant spring, and alpha thalassemia major. The most common deletion reported in alpha thalassemia in. Pdf alpha thalassemia deletions found in suspected cases of beta. There are two main types of thalassemia, alpha thalassemia and beta thalassemia. Alphaglobin is coded on two consecutive genes on chromosome 16, meaning each diploid erythrocyte precursor carries four total alphaglobin alleles. It is a blood disorder that reduces how well the body produces healthy red blood cells and normal hemoglobin. Alpha thalassemia hba1 and hba2 7 deletions dna test. The chance of finding deletions may be lower if you come from an ethnic population where the rate of alphathalassemia is rare or unknown. Detection of common deletional alphathalassemia spectrum. Being a silent carrier means you dont have signs of the disease, but you can pass the damaged gene on to your child. Mutation of both alpha2 globin genes, or deletion of alpha1 and alpha2 globin genes in cis.
Individuals with alphathalassemia carry deletions that affect any combination of these loci, meaning there might be absent synthesis from one, two, three, or all four alphaglobin loci. Carrier frequencies are often 1% due to a selective advantage of malaria resistance in. Alphathalassemia is a blood disorder that reduces the bodys production of hemoglobin. Alpha thalassemia childrens hospital of philadelphia. The cardiothoracic ratio, placental thickness, and middle cerebral artery peak systolic velocity are most used in. The most severe form of alpha thalassemia is alpha thalassemia major or barts hydrops fetalis. Alpha thalassemia minor or alpha thalassemia1 trait are other terms for this condition. Alpha thalassemia typically results from deletions involving the hba1 and hba2 genes. Alphathalassemia is characterized by a deficit in the production of the. Alpha thalassemia is a blood disorder that reduces the production of hemoglobin. In most ethnic groups where alphathalassemia is common, deletions account for approximately 90% of the alphaglobin gene mutations.
A simple dna test can be completed to determine whether or not an individual has one or more of the seven common deletions in the hba1 and hba2 genes that reduce the levels of. The alphaglobin common mutation analysis test test code 11175 11174 for ny can detect the seven most common deletions and identify whether the deletions are in cis or in trans. The types of alphathalassemia mutations are variable depending on geographic region. Evaluation of alphathalassemia mutations in cases with. Deletion of 1 allele results in the silent form, 2 alleles in alphathalassemia trait, and 3 alleles in hbh. However, the homozygous state with both genes for alpha thalassemia is lethal before birth because no alpha chains can be made and without alpha chains, there can be no hb f or hb a and without hb f or hb a, the inevitable result is an unsuccessful pregnancy. Defects in these genes result in alpha thalassemia, which is a common hemoglobin disorder commonly found in african and asian populations. Alphathalassemia is of particular importance to neonatologists because its clinical manifestations are present in utero and at birth. The ethnic composition of the brazilian population favors high frequencies of the alpha3. Alpha thalassemia is caused most frequently by deletions involving one or both. Alpha gene mapping can be obtained to determine the specific mutation. Alphathalassemia is usually inherited in an autosomal recessive manner. Thalassemia is an inherited blood disorder that reduces the production of functional hemoglobin the protein in red blood cells that carries oxygen. Alpha thalassemia is particularly common in china and southeast asia, with up to 40% of the regional population being carriers.
Both of these genes provide instructions for making a protein called alphaglobin, which is a component subunit of hemoglobin people have two copies of the hba1 gene and two copies of the hba2 gene in each cell. The alpha thalassemias are caused by a decrease in production of alpha globin chains due to a deletion or mutation of one or more of the four alpha globin genes located on chromosome 16. Thalassemia prevails in southeast asia, where thalassemia major is a lethal type. Alpha thalassemia is a blood disorder that reduces the production of normal hemoglobin, the protein in red blood cells that carries oxygen to cells throughout the body there are four types of alpha thalassemia, hemoglobin bart hydrops fetalis syndrome or hb bart syndrome the more severe form, hbh disease. This disease occurs when all four alpha genes are missing. Alpha thalassemia an overview sciencedirect topics. Alphathalassemia is a group of disorders of hemoglobin synthesis, caused by mutations or deletions in at least 1 of the 4 alphaglobin genes, leading to variably impaired alphaglobin chain production, with accumulation of the now excess and unpaired betaglobin chains. A single gene deletion results in alpha thalassemia silent carrier status, alpha chainwhich is asymptomatic with normal hematologic findings. Affected people have anemia, which can cause pale skin, weakness, fatigue, and more serious complications.
Lim wf, muniandi l, george e, sathar j, teh lk and lai mi. The mutations are inherited in an autosomal recessive pattern, which means that you need mutated genes from both parents to get the disease. It can be successfully treated provided the pregnancy is anticipated or the diagnosis is made early with ultrasound and genetic testing of the fetus. Hemoglobin a, the main form of hemoglobin, is a polypeptide comprised of two alpha and two beta chains. Alphathalassemia is one of the most common hemoglobin genetic. These videos are designed for medical students studying for the usmle step 1.
The alpha thalassemias can be generally categorized as. Alpha thalassemia nord national organization for rare. People who have this condition can pass the disease on. Frequently, the diagnosis of alpha thalassemia trait in a parent is discovered after the birth of an affected child. The diagnosis of alphathalassemia is also important in patients with unsolved hypochromic microcytic anemia. Alpha thalassemia deletions found in suspected cases of beta. Alpha chains are encoded through the hba1 and hba2 genes.
Alpha thalassemia is a general term for a group of inherited blood disorders characterized by reduced or absent production of alphaglobin subunits, resulting in low levels of hemoglobin that is otherwise fully functional. Hemoglobin is an ironrich protein in red blood cells that carries oxygen to cells throughout the body. Males with this condition tend to be moderately intellectually disabled and have physical characteristics including coarse facial features, microcephaly small head. Detection of common deletional alphathalassemia spectrum by. Molecular diagnosis of thalassemias and hemoglobinopathies. Normally, a second newborn screening test will not detect this condition. Thalassemia is a significant public health burden in affected regions, 1 and thus prenatal screening and genetic counseling are important in preventing the most severe forms of thalassemia. Alphathalassemia mental retardation syndrome wikipedia. Read on to know all about its various types, symptoms and possible treatment options. The molecular basis for alphathalassemia is usually deletion of one or more of the. Thalassemia is a genetic blood disorder that impacts the ability of the blood to get oxygen to the bodys organs. Two types of alphathalassemia can cause health problems. If a large number of barts hemoglobin and hemoglobin h genes are present on the newborn screening test, it usually means the baby has hemoglobin h. The most common deletion reported in alpha thalassemia in pakistani population was.
Alphathalassemia is one of the most common hemoglobin genetic abnormalities. If one parent has a deletion that only removes a single. Thalassemia knowledge for medical students and physicians. Alphathalassemia genetic and rare diseases information.
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