Thalassemia
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Defects in protein structure or synthesis of hemoglobin are called hemoglobinopathies. Thalassemia is the most common hemoglobinopathy, and it is estimated that 5% of the world population carries at least one variant allele of thalassemia. The thalassemias can be classified as alpha or beta thalassemias. Beta thalassemia may present as silent carriers with normal hematological parameters, while beta thalassemia carriers have hypochromic microcytic anemia, associated with a high HbA2. However, patients with beta thalassemia intermedia and beta thalassemia major need transfusion intermittently or regularly and they are called non-transfusion dependent thalassemias or transfusion-dependent thalassemias, respectively. This review focuses on pathophysiology, clinical, laboratory features of thalassemias along with their treatment and follow-up.Keywords:
Hemoglobinopathy
Alpha-thalassemia
Beta thalassemia
Genetic hemoglobin disorders are caused by mutations and/or deletions in the α-globin or β-globin genes. Thalassemia is caused by quantitative defects and hemoglobinopathies by structural defect of hemoglobin. The incidence of thalassemia and hemoglobinopathy is increased in Korea with rapid influx of people from endemic areas. Thus, the awareness of the disease is needed. α-thalassemias are caused by deletions in α-globin gene, while β-thalassemias are associated with decreased synthesis of β-globin due to β-globin gene mutations. Hemoglobinopathies involve structural defects in hemoglobin due to altered amino acid sequence in the α- or β-globin chains. When the patient is suspected with thalassemia/hemoglobinopathy from abnormal complete blood count findings and/or family history, the next step is detecting hemoglobin abnormality using electrophoresis methods including high performance liquid chromatography and mass spectrometry. The development of novel molecular genetic technologies, such as massively parallel sequencing, facilitates a more precise molecular diagnosis of thalassemia/hemoglobinopathy. Moreover, prenatal diagnosis using genetic testing enables the prevention of thalassemia birth and pregnancy complications. We aimed to review the spectrum and classification of thalassemia/hemoglobinopathy diseases and the diagnostic strategies including screening tests, molecular genetic tests, and prenatal diagnosis.
Hemoglobinopathy
Hemoglobin electrophoresis
Beta thalassemia
Hemoglobin variants
Alpha-thalassemia
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Hemoglobinopathy includes structural abnormalities and haemoglobin synthesis disorders (thalassemia), is a single gene disorder that was originally found in malaria endemic areas but nowadays can be found all over the world. The birth rate of homozygous or compound heterozygous hemoglobinopathies, including alpha and beta thalassemia is less than 2.4 per 1000 births. Sickle cell anemia is the most prevalent compared to beta major and HbE-beta thalassemia. In Southeast Asia with more than 600 million people, abnormalities in hemoglobin including thalassaemia, HbE and HbCS are the most common and highly prevalent genetic disorders. Indonesia, has several areas that are endemic to malaria, there are many cases of abnormalities in Hb including thalassemia. If the percentage of carriers is associated with the birth rate and the number of Indonesian population and based on the study, it is estimated that the number of thalassemia patients born each year around 2500 children. As the case of thalassemia is increasing from year to year, it is necessary that prevention starts with screening in individuals who have relatives known as a carrier or thalassemia patient.
Hemoglobinopathy
Beta thalassemia
Alpha-thalassemia
Hemoglobin E
Ineffective erythropoiesis
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Thalassemia and hemoglobinopathy are two common inherited disorders, which are highly prevalent in southern China. However, there is little knowledge on the genotypes of thalassemia and hemoglobinopathy in Southeastern China. In this study, we present a large-scale genetic detection and molecular characterization of thalassemia and hemoglobinopathy in Fujian province, Southeastern China. A total of 189414 subjects screened for thalassemia were recruited, and the hemoglobin components and levels were investigated. Furthermore, suspected common thalassemia was identified, and the suspected rare forms of common thalassemias and hemoglobinopathy were detected. Among the total subjects screened, the overall prevalence of thalassemia and hemoglobinopathy was 6.8% and 0.26%, and rare α-thalassemia genotypes HKαα, –THAI/αα and −α27.6/αα, and novel β-thalassemia gene mutations CD90(G → T) and IVS-I-110(G > A) were identified. Additionally, Hb Q-Thailand hemoglobinopathy and five other types of hemoglobinopathies (Hb New York, Hb J-Bangkok, Hb G-Taipei, Hb G-Coushatta and Hb Maputo) were found. The results of this 10-year large-scale study demonstrate high prevalence of thalassemia with complicated gene mutations in Southeastern China, which provides valuable baseline data for genetic counseling and prenatal diagnosis. In addition to detection of common thalassemia genes, detection of rare thalassemia genotypes and hemoglobinopathies is recommended.
Hemoglobinopathy
Beta thalassemia
Hemoglobin variants
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Beta-thalassemias are prevalent heritable single gene disorders affecting the quantity of the hemoglobin molecule. Rarely, a co-inheritance of these impairments with alpha-thalassemia and/or a hemoglobinopathy occurs and makes an important double heterozygote or homozygous state. Thus finding these cases is essential for genetic counseling. The present study aimed to identify the prevalence of coexistent alpha-thalassemia mutations, hemoglobinopathies, and beta-thalassemia determinants.This descriptive study was performed on 5760 patients. We used complete blood cell count, Hb electrophoresis, and HbA2 measurement for thalassemia carrier identification. Increased HbA2 (> or = 3.5%) is the standard diagnostic marker for beta-thalassemia, while normal HbA2 with low MCH and MCV can indicate an alpha-thalassemia carrier or atypical beta-thalassemia minor. Individuals with MCV < 80 fL, MCH < 27 pg, and hemoglobin < or = 15.3 g/dL in men or < or = 14 g/dL in women, were candidates for molecular thalassemia investigations. Patients with abnormal hemoglobin varieties in hemoglobin electrophoresis were referred to a genetics laboratory for hemoglobinopathy detection.141 subjects out of 5760 were affected by alpha and beta-thalassemia or a beta-hemoglobinopathy simultaneously, including: 13 (11.1%) fetuses, 55 (38.2%) male cases, and 73 (50.7%) females. Among these 141 alpha-thalassemia patients, 92 cases (65.24%) were beta-thalassemia carriers and 3 (2.12%) were beta-thalassemia major, 43(30.49%) had beta-hemoglobinopathies, and 3 cases (2.12%) had co-inherited beta-thalassemia and variant hemoglobins. 31 beta-gene mutations were observed in this population, the most common being HbS Cd6 (A > T) (24%). These thalassemia determinants account for about 46% of all detected mutations. As for alpha-gene mutations, -3.7 detection was the most prevalent.The relatively high prevalence of co-inherited alpha-thalassemia and hemoglobinopathies among beta-thalassemia carriers indicates the importance of molecular analysis to diagnose these double heterozygous or sole homozygous cases for prenatal diagnostic purposes and putting forth strategies to prevent more complicated and dangerous combinations.
Hemoglobinopathy
Beta thalassemia
Alpha-thalassemia
Hemoglobin electrophoresis
Heterozygote advantage
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The study of 176 subjects with beta-thalassemia, associated or not with a hemoglobinopathy, shows great diversity. The hemoglobin C thalassemias are less severe and form a fairly homogeneous group. Sickle cell thalassemia cases have more marked anemia and the disease takes on more varied forms, no doubt because the main mechanism of the anemia, the hyperhemolysis, is influenced by several factors which have a variable effect on the clinical picture. Unassociated thalassemias seem the most polymorphic. Although it seems that in certain foci the beta-thalassemias are fairly stereotyped, this first study shows in Algeria great heterogeneity. All forms are observed both clinically and in the laboratory. Present classifications have not supplied a sufficiently operative model. It is not doubt necessary to await further progress in the laboratory to classify these diseases more precisely.
Hemoglobinopathy
Beta thalassemia
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A program for the detection of thalassemias and other hemoglobinopathies in high-risk populations is described. This program, based on two screening tests, was applied to the Hellenic Army recruits and was found to work well. Red cell one-point osmotic fragility was used for the detection of thalassemic samples and hemoglobin electrophoresis for screening of other hemoglobinopathies. Samples with decreased red cell osmotic fragility and/or abnormal electrophoretic pattern were submitted for further detailed investigation. Following this program, 64,814 recruits, representing 0.651% of the total Greek population and 9.917% of the 20-year-old Greek male population, were tested. beta-Thalassemia was found with an average incidence of 5.476% and alpha-Thalassemia with an incidence of 0.201%. Hemoglobinopathy Lepore was detected in 51 samples (0.079%) and hemoglobinopathy-S in 352 samples (0.543%).
Hemoglobinopathy
Erythrocyte fragility
Beta thalassemia
Hemoglobin electrophoresis
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Beta thalassemia
Hemoglobinopathy
Alpha-thalassemia
Beta-thalassaemia
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A program for the detection of thalassemias and other hemoglobinopathies in high-risk populations is described. This program, based on two screening tests, was applied to the Hellenic Army recruits and was found to work well. Red cell one-point osmotic fragility was used for the detection of thalassemic samples and hemoglobin electrophoresis for screening of other hemoglobinopathies. Samples with decreased red cell osmotic fragility and/or abnormal electrophoretic pattern were submitted for further detailed investigation. Following this program, 64,814 recruits, representing 0.651% of the total Greek population and 9.917% of the 20-year-old Greek male population, were tested. β-Thalassemia was found with an average incidence of 5.476% and α-Thalassemia with an incidence of 0.201%. Hemoglobinopathy Lepore was detected in 51 samples (0.079%) and hemoglobinopathy-S in 352 samples (0.543%).
Hemoglobinopathy
Erythrocyte fragility
Hemoglobin electrophoresis
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Citations (1)
Defects in protein structure or synthesis of hemoglobin are called hemoglobinopathies. Thalassemia is the most common hemoglobinopathy, and it is estimated that 5% of the world population carries at least one variant allele of thalassemia. The thalassemias can be classified as alpha or beta thalassemias. Beta thalassemia may present as silent carriers with normal hematological parameters, while beta thalassemia carriers have hypochromic microcytic anemia, associated with a high HbA2. However, patients with beta thalassemia intermedia and beta thalassemia major need transfusion intermittently or regularly and they are called non-transfusion dependent thalassemias or transfusion-dependent thalassemias, respectively. This review focuses on pathophysiology, clinical, laboratory features of thalassemias along with their treatment and follow-up.
Hemoglobinopathy
Alpha-thalassemia
Beta thalassemia
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Citations (4)
In Southeast Asia alpha-thalassemia, beta-thalassemia, hemoglobin (Hb) E and Hb Constant Spring are prevalent. The gene frequencies of alpha-thalassemia reach 30-40% in Northern Thailand and Laos. beta-Thalassemia gene frequencies vary between 1 and 9%. Hb E is the hallmark of Southeast Asia attaining a frequency of 50-60% at the junction of Thailand, Laos, and Cambodia. Hb Constant Spring gene frequencies vary between 1 and 8%. These abnormal genes in different combinations lead to over 60 different thalassemia syndromes. The four major thalassemic diseases are Hb Bart's hydrops fetalis (homozygous alpha-thalassemia 1), homozygous beta-thalassemia, beta-thalassemia/Hb E and Hb H diseases. The molecular basis of most of these abnormal genes have been recently described. Therefore, it is possible to set a strategy for prevention and control of thalassemia which includes population screening for heterozygotes, genetic counseling and fetal diagnosis with selective abortion of affected pregnancies.
Hydrops fetalis
Hemoglobinopathy
Beta thalassemia
Alpha-thalassemia
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