Blood tests are usually normal and the only way to confirm a silent carrier is by dna studies. The severity of alpha and beta thalassemia depends on how many of the four genes for alpha globin or two genes for beta globin are missing. The type of treatment a person receives depends on how severe the thalassemia is. This disorder is caused by mutations in the beta chain of the hemoglobin molecule. A loss of two of the four alphaglobin alleles results in alpha thalassemia trait. The nhs sickle cell and thalassaemia screening programme also has detailed leaflets about being a beta thalassaemia carrier pdf, 804kb or a delta beta thalassaemia carrier pdf, 779kb. Frequently, the diagnosis of alpha thalassemia trait in a parent is discovered after the birth of an affected child. Silent alpha thalassemia carrier one alpha chain gene is deleted the other three are normal. Alpha thalassemia nord national organization for rare. The first type of alpha thalassemia trait has one alpha gene missing on each chromosome aa. In thailand, which has a population of 62 million people, approximately 7000 infants are born each year with hbh disease.
The carrier frequency is estimated to be 1 in 30 for african americans and 1 in 30 50 for mediterranean populations. Alpha thalassemia is a fairly common blood disorder worldwide. The program is designed to address the complex diagnostic, prenatal, intrauterine, and perinatal management issues affecting a family with an alpha thalassemia major pregnancy. The invitae comprehensive carrier screen includes up to 301 genes and is appropriate for those of all ethnicities who want an expanded assessment of their risk of having an affected child. Alpha thalassemia indications for ordering carrier screening o healthy individuals of african, mediterranean, middle eastern, and southeast asian descent o individuals with a family history of alpha. The most severe form of alpha thalassemia, which affects mainly. It can affect people of any ethnicity, but is more common in people who can trace their ancestry to southeast asia, india, equatorial africa, the mediterranean, or the arabian peninsula. Normally two alpha hemoglobin genes are inherited from each parent, one hba1 gene and one hba2 gene, for a total of four alpha hemoglobin genes. The frequency of thalassaemia syndromes in sardinia was examined by a population survey. Individuals in southeast asia are more likely to have all four possibilities estimates of carrier frequency are carrier frequency in other populations is not certain. The genes associated with alphathalassemia can be added at no additional charge. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Ancestry based carrier screening flashcards quizlet. Alphathalassemia silent carriers may have normal hematologic findings or may have a moderate, thalassemialike hematologic picture similar to individuals with.
Thousands of infants with hb bart syndrome and hbh disease are born each year, particularly in southeast asia. The alpha thalassemias can be generally categorized as. Thalassemia is considered one of the most common genetic disorders in the world, with a high frequency in tropical and subtropical areas such as. Detection of common deletional alphathalassemia spectrum. The carrier frequency and incidence of alpha thalassemia vary by the type and population. Alpha thalassemia trait a person with two working copies of the alpha globin gene has alpha thalassemia trait. People with hemoglobin h disease can have an enlarged spleen, low red blood cell. The alpha 1 and alpha 2 globin genes are located close together in a region of each chromosome 16 known as the alphaglobin locus.
Even though the mechanism is still unknown, it is believed that, like the other hemoglobin related disorders. There are two different types of alpha thalassemia trait. One missing or abnormal gene makes a child a silent alpha thalassemia carrier. Alphathalassemia is most frequent in southeast asian populations, where the incidence of hbh disease is between 4 and 20 per births, and the incidence of hb bart syndrome is between 0. Carrier frequency of this condition is reported to be the highest in. The carrier frequency is estimated to be 1 in 30 for african americans and 1 in 3050 for mediterranean populations. 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.
If two genes are missinga person has alpha thalassemia trait also called alpha thalassemia minor and may have mild anemia. Study conducted at fatima jinnah medical college lahore by majeed17on family members of thalassemia major patients showed a frequency of 52% for beta thalassemia trait with female population of 51. Patients suffering from either alpha or beta thalassemia often undergo blood transfusion which is the only treatment option for such patients. It is a genetic trait passed down from parents to children. A negative carrier screening result reduces the risk for a patient to be a carrier of a specific disease but does not completely rule out carrier status. It is thought that all of these globin gene disorders including. But you are a carrier of the disease and can pass it on to your children. Betathalassemia results from reduced synthesis of the hemoglobin beta chain. Individuals with alpha thalassemia silent carrier and alpha thalassemia minor usually do not develop symptoms and do not require treatment. If a parent is missing one or two of these genes, then. These detailed results of alpha thalassaemia allele frequency and genetic. Alpha thalassemia is a blood disorder that reduces the production of hemoglobin.
Silent alpha thalassemia carriers have no signs or symptoms of the disease, but. Four genes are involved in making the alpha hemoglobin chain. Alpha thalassemia is particularly common among populations of southeast asian descent, and there are a high number of carriers in subsaharan africa and western pacific regions. Carrier frequencies for common genetic diseases by ethnicity. Over two million people in the united states carry the genetic trait for thalassemia. Alphathalassemia is usually inherited in an autosomal recessive manner. The ucsf fetal treatment center and ucsf benioff childrens hospitals have established the first multidisciplinary center for alpha thalassemia major. Carrier frequency, detection rates and residual risks are available here. A mutation in one alpha gene results in slightly lower production of functional alpha chains and does not cause any symptoms silent alpha thalassemia carrier. Thalassemia is a type of thalassemia that is caused by a deficiency of the alpha globin protein. These individuals typically have no thalassemiarelated signs or symptoms.
Below are the carrier rates, detection rates, and residual risks for the conditions on horizon 27 panethnic basic. If one parent has the cis form of alpha thalassemia trait, and the other parent is a silent carrier. The more severe the thalassemia, the less hemoglobin the body has, and the more severe the anemia may be. Like the silent carrier, alpha thalassemia trait is not a disease and does not affect your health. The frequency of transfusion varies from 24 weeks depending upon the patients condition. The frequency of heterozygote carrier status among the chinese population has been reported to range from 5% to 15%. Beta thalassemia cooleys anemia childrens wisconsin. The high frequency panethnic panel provides carrier screening for the following genetic disorders due to the relatively elevated carrier frequencies and high detection rates in most ethnic groups with severe, early onset clinical presentation. What is the global prevalence of alpha thalassemia. A comprehensive ethnicbased analysis of alpha thalassaemia.
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. Alphathalassemia types, causes, diagnosis, treatment. People with alpha thalassemia trait may have unusually small, pale red blood cells and mild anemia. For information about carrier frequency and residual risk, please see the. Frequency is also increased in mediterranean countries, the middle east, india, central asia and north africa. Detecting and reporting alpha thalassemia in newborns. Alphathalassemia is an autosomal recessive condition that affects the red blood cells. Alphathalassemia genetic and rare diseases information. Most individuals with alpha thalassemia have milder forms of the disease, with varying degrees of anemia. The frequency of alpha thalassemia alleles is 510 % in the mediterranean basin, 2030 % in portions of west africa, and as high as 6080 % in parts of saudi arabia, india, thailand, papua new guinea, and melanesia. Identification relies on molecular genetic testing of the. One mutated gene, youll have no signs or symptoms of thalassemia. The invitae comprehensive carrier screen includes up to 301 genes and is appropriate for.
Impaired 1, 2, 3, or 4 alpha globin chain productions can lead to a comparative excess of the beta globin chains. Different forms of alpha thalassemia occur if one or more of these genes are missing. Although thalassemia mostly affects developing countries, there is limited knowledge of its accurate frequency and distribution in these regions. The trans form of alpha thalassemia trait aa is common in africanamericans 2030% and in people of african descent. Normal hemoglobin has two alpha and two beta peptide chains. One way to treat anemia is to provide the body with more red blood cells to. Alphathalassemia, betathalassemia, betaglobinrelated hemoglobinopathies. Alpha thalassemia is an inherited autosomal recessive disorder caused by a complete absence or decrease in the production of alpha globin peptides due to a deletion or mutation of one or more of the four alpha. Yusuf clinical presentation of alpha thalassemia hemoglobin barts percentages hemoglobin constant spring alpha thalassemia screening status in the us hemoglobins on the rusp.
There are two main types, alpha thalassemia and beta thalassemia. Alphathalassemia trait reaches very high allele frequency 0. A trait carrier of thalassemia will always be a trait carrier. Silent carrier, alpha thalassemia trait, hemoglobin h disease, hemoglobin hconstant spring, and alpha thalassemia major. A child of two carriers has a 25 percent chance of receiving two trait genes and developing the disease, and a 50 percent chance of being a thalassemia trait carrier. Rare cases of learning difficulties have been associated with alpha thalassemia. Beta thalassemia, alpha thalassemia, sickle cell disease, cystic fibrosis, g6pd deficiency what is the carrier frequency of beta thalassemia in individuals of mediterranean ancestry.
Alpha thalassemia trait and beta thalassemia trait. A loss of one alphaglobin allele is found in alpha thalassemia silent carriers. The frequency of carriers for alpha thal is about one in 30 in persons who are southeastern asian or chinese. This is called the trans form of alpha thalassemia trait. You can find out if youre a carrier of thalassaemia by having a simple blood test. It is important that individuals with alpha thalassemia minor be correctly diagnosed, however, in order to avoid unnecessary treatments for similarly appearing conditions such as iron deficiency anemia. Knowing the prevalence of thalassemia and the frequency of responsible mutations is therefore an important step. Frequency of beta thalassemia trait in females was 24. Alpha thalassemia trait causes the size of the red blood cells to be smaller than usual.
Pdf thalassemia types and their incidence in sardinia. Diagnosis is typically by blood tests including a complete blood count, special hemoglobin tests, and genetic tests. Anyone can be a carrier of thalassaemia, but its much more common in people from certain ethnic backgrounds. Frequency of carrier rate of beta beta thalassemia. If one gene is missinga person is a silent carrier of alpha thalassemia and usually has no signs or symptoms. Alpha thalassemia also occurs frequently in people from mediterranean countries, africa, the middle east, india, and central asia. Alphathalassemia is inherited in an autosomal recessive manner. Alpha thalassemia arup lab test directory arup laboratories. The frequency of this gene in the general population is about one in 300, while persons who are of mediterranean ancestry greek or italian have a risk of about one in 30 for carrying this gene. Thalassemia is a hereditary blood disorder that results from genetic defects causing deficient synthesis of hemoglobin polypeptide chains. One gene is missing or damaged, and the other 3 are normal.
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