Detecting and reporting alpha thalassemia in newborns. Individuals with alpha thalassemia silent carrier and alpha thalassemia minor usually do not develop symptoms and do not require treatment. If two genes are missinga person has alpha thalassemia trait also called alpha thalassemia minor and may have mild anemia. Alpha thalassemia arup lab test directory arup laboratories. Silent alpha thalassemia carriers have no signs or symptoms of the disease, but. Beta thalassemia cooleys anemia childrens wisconsin. One missing or abnormal gene makes a child a silent alpha thalassemia carrier. 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. Frequency is also increased in mediterranean countries, the middle east, india, central asia and north africa. Carrier frequency of this condition is reported to be the highest in. 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. The alpha thalassemias can be generally categorized as. 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.
The frequency of heterozygote carrier status among the chinese population has been reported to range from 5% to 15%. 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. Thalassemia is considered one of the most common genetic disorders in the world, with a high frequency in tropical and subtropical areas such as. But you are a carrier of the disease and can pass it on to your children. Alphathalassemia, betathalassemia, betaglobinrelated hemoglobinopathies.
It is thought that all of these globin gene disorders including. Alphathalassemia is inherited in an autosomal recessive manner. Even though the mechanism is still unknown, it is believed that, like the other hemoglobin related disorders. 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. The type of treatment a person receives depends on how severe the thalassemia is. The ucsf fetal treatment center and ucsf benioff childrens hospitals have established the first multidisciplinary center for alpha thalassemia major. 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. Silent alpha thalassemia carrier one alpha chain gene is deleted the other three are normal. 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. Frequently, the diagnosis of alpha thalassemia trait in a parent is discovered after the birth of an affected child. Betathalassemia results from reduced synthesis of the hemoglobin beta chain. Four genes are involved in making the alpha hemoglobin chain. Alpha thalassemia trait causes the size of the red blood cells to be smaller than usual.
Alphathalassemia is usually inherited in an autosomal recessive manner. 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. Alphathalassemia silent carriers may have normal hematologic findings or may have a moderate, thalassemialike hematologic picture similar to individuals with. Carrier frequency, detection rates and residual risks are available here. The program is designed to address the complex diagnostic, prenatal, intrauterine, and perinatal management issues affecting a family with an alpha thalassemia major pregnancy. 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. Patients suffering from either alpha or beta thalassemia often undergo blood transfusion which is the only treatment option for such patients. A loss of two of the four alphaglobin alleles results in alpha thalassemia trait. 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. What is the global prevalence of alpha thalassemia. Pdf thalassemia types and their incidence in sardinia.
The carrier frequency is estimated to be 1 in 30 for african americans and 1 in 3050 for mediterranean populations. Ancestry based carrier screening flashcards quizlet. 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. Thalassemia is a hereditary blood disorder that results from genetic defects causing deficient synthesis of hemoglobin polypeptide chains. Alphathalassemia is an autosomal recessive condition that affects the red blood cells. 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. A trait carrier of thalassemia will always be a trait carrier. Alphathalassemia types, causes, diagnosis, treatment. Alpha thalassemia nord national organization for rare. Most individuals with alpha thalassemia have milder forms of the disease, with varying degrees of anemia.
Rare cases of learning difficulties have been associated with alpha thalassemia. Impaired 1, 2, 3, or 4 alpha globin chain productions can lead to a comparative excess of the beta globin chains. Alpha thalassemia is a fairly common blood disorder worldwide. 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. Beta thalassemia, alpha thalassemia, sickle cell disease, cystic fibrosis, g6pd deficiency what is the carrier frequency of beta thalassemia in individuals of mediterranean ancestry.
In thailand, which has a population of 62 million people, approximately 7000 infants are born each year with hbh disease. Over two million people in the united states carry the genetic trait for thalassemia. Alphathalassemia genetic and rare diseases information. A comprehensive ethnicbased analysis of alpha thalassaemia. Below are the carrier rates, detection rates, and residual risks for the conditions on horizon 27 panethnic basic. What if one parent has alpha thalassemia trait and the other parent is a silent carrier. Alpha thalassemia trait a person with two working copies of the alpha globin gene has alpha thalassemia trait. Alphathalassemia trait reaches very high allele frequency 0. Normal hemoglobin has two alpha and two beta peptide chains. The frequency of thalassaemia syndromes in sardinia was examined by a population survey. If one gene is missinga person is a silent carrier of alpha thalassemia and usually has no signs or symptoms. Thalassemia is a type of thalassemia that is caused by a deficiency of the alpha globin protein. 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 genes associated with alphathalassemia can be added at no additional charge. The frequency of transfusion varies from 24 weeks depending upon the patients condition. Frequency of beta thalassemia trait in females was 24. Alpha thalassemia is a blood disorder that reduces the production of hemoglobin. 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. Frequency of carrier rate of beta beta thalassemia.
One way to treat anemia is to provide the body with more red blood cells to. Alpha thalassemia trait and beta thalassemia trait. Knowing the prevalence of thalassemia and the frequency of responsible mutations is therefore an important step. This is called the trans form of alpha thalassemia trait. 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. Alpha thalassemia also occurs frequently in people from mediterranean countries, africa, the middle east, india, and central asia. The most severe form of alpha thalassemia, which affects mainly. Diagnosis is typically by blood tests including a complete blood count, special hemoglobin tests, and genetic tests. There are two different types of alpha thalassemia trait. People with hemoglobin h disease can have an enlarged spleen, low red blood cell.
Anyone can be a carrier of thalassaemia, but its much more common in people from certain ethnic backgrounds. Blood tests are usually normal and the only way to confirm a silent carrier is by dna studies. One mutated gene, youll have no signs or symptoms of thalassemia. Silent carrier, alpha thalassemia trait, hemoglobin h disease, hemoglobin hconstant spring, and alpha thalassemia major. Thousands of infants with hb bart syndrome and hbh disease are born each year, particularly in southeast asia. 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. The more severe the thalassemia, the less hemoglobin the body has, and the more severe the anemia may be. Detection of common deletional alphathalassemia spectrum.
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. 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. The carrier frequency is estimated to be 1 in 30 for african americans and 1 in 30 50 for mediterranean populations. One gene is missing or damaged, and the other 3 are normal. The first type of alpha thalassemia trait has one alpha gene missing on each chromosome aa. The trans form of alpha thalassemia trait aa is common in africanamericans 2030% and in people of african descent.
The frequency of carriers for alpha thal is about one in 30 in persons who are southeastern asian or chinese. If one parent has the cis form of alpha thalassemia trait, and the other parent is a silent carrier. You can find out if youre a carrier of thalassaemia by having a simple blood test. For information about carrier frequency and residual risk, please see the. 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. Like the silent carrier, alpha thalassemia trait is not a disease and does not affect your health. 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. 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. Different forms of alpha thalassemia occur if one or more of these genes are missing.
These detailed results of alpha thalassaemia allele frequency and genetic. The alpha 1 and alpha 2 globin genes are located close together in a region of each chromosome 16 known as the alphaglobin locus. If a parent is missing one or two of these genes, then. Identification relies on molecular genetic testing of the. The carrier frequency and incidence of alpha thalassemia vary by the type and population. Carrier frequencies for common genetic diseases by ethnicity.