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PubMed2003

Sleep disruption and objective sleepiness in children with beta-thalassemia and congenital dyserythropoietic anemia.

BACKGROUND: Sleep fragmentation and periodic leg movement syndrome (PLMS) have been reported in adults with iron deficiency anemia. Little is known about sleep function and daytime sleepiness in children with chronic anemia such as beta-thalassemia or congenital dyserythropoietic anemia type 1 (CDA-1). OBJECTIVES: To investigate if children and adolescents who have beta-thalassemia (major or intermedia) or CDA-1 experience sleep fragmentation and objective daytime sleepiness and also to investigate if children and adolescents with beta-thalassemia have obstructive sleep apnea. METHODS: Ten patients (7 males and 3 females) with beta-thalassemia (mean [SD] age, 10.4 [7.3] years), 10 patients (7 males and 3 females) with CDA-1 (mean [SD] age, 13.5 [5.1] years), and 13 healthy volunteer control children(7 males and 6 females) (mean [SD] age, 10 [4] years) underwent nocturnal polysomnographic studies. A multiple sleep latency test was performed for 6 patients who had beta-thalassemia and 8 patients who had CDA-1. RESULTS: Both patient groups, that is, those who had beta-thalassemia and those who had CDA-1, had multiple arousals during sleep (mean [SD], 27.8 [11.4] events per hour and 23.8 [11.8] events per hour, respectively) compared with the control subjects (12.1 [6.6] events per hour) (P<.002). Thirty-eight percent (10.6 events per hour) of the arousals in patients with beta-thalassemia and 25% (6.0 events per hour) of the arousals in patients with CDA-1 were induced by periodic limb movements during sleep. In the control group, most (98%) arousals were spontaneous and unrelated to any definable event. The multiple sleep latency test average was 7.8 minutes for patients with beta-thalassemia (n = 6) and 10.7 minutes for patients with CDA-1 (n = 8). Five patients with beta-thalassemia and 4 patients with CDA-1 underwent a second polysomnographic study on the next night to confirm reproducibility. There was no significant change in the total number or index of arousals and no difference in the severity of the periodic limb movements during sleep compared with the results of the first polysomnographic study. CONCLUSION: Children and adolescents with beta-thalassemia or CDA-1 have evidence of impaired sleep function that is partially due to periodic limb movements during sleep and arousals that result in objective diurnal sleepiness.

Adolescent↗
PubMed1998

Detection of zeta-globin chains in the cord blood by ELISA (enzyme-linked immunosorbent assay): rapid screening for alpha-thalassemia 1 (Southeast Asian type).

Fetuses with homozygous alpha-thalassemia 1, in which the deletion of all four alpha-globin genes results in the absence of any alpha-globin chains, are severely anemic with clinical features of hydrops fetalis. Definitive diagnosis of alpha-thalassemia 1 carriers is difficult since there are few red cell abnormalities. Recently Chui et al. found that minute amounts of embryonic zeta-globin chains are present in adult hemoglobin of the Southeast Asian type of alpha-thalassemia 1 carriers. In this study, we screened 521 cord bloods for alpha-thalassemia 1. Hemoglobin analysis, including quantitation of Hb Bart's, was performed using the automated HPLC, alpha-thalassemia short program (VARIANT, Bio-Rad, Hercules, CA). Of these, 200 cord blood samples in which Hb Bart's was demonstrated were tested for the presence of zeta-globin chains by ELISA using labeled anti-zeta monoclonal antibody. Zeta-globin ranged between 0.21 and 0.83% in 19 specimens carrying alpha-thalassemia 1 gene. In the remaining 90 out of 109 specimens in which Hb Bart's was greater than 1.2%, zeta-globin was less than 0.17%. DNA analysis revealed the presence of normal alpha-genotype and other types of alpha-thalassemia including alpha-thalassemia 2 and Hb Constant Spring. One false positive was found in which the zeta-globin was 0.25% by ELISA but in which PCR indicated an alpha-thalassemia 2 heterozygote. Ninety-one samples with Hb Bart's of less than 1.2% by HPLC are most likely normal with a zeta-globin range between 0 and 0.14%. This study also showed that the frequency of alpha-thalassemia 1 in Bangkok is 3.65%.

Adult↗
PubMed1992

Molecular basis of beta thalassemia in the south of Thailand.

A total of 103 beta thalassemia genes from 78 children (45 with Hb E/beta thalassemia, 8 with beta thalassemia heterozygotes, and 25 with homozygous beta thalassemia) were analyzed using dot-blot hybridization of the polymerase chain reaction-amplified DNA and direct DNA sequencing. Nine mutations were characterized in 98/103 (95%) of beta thalassemia alleles, of which six (a 4 bp deletion in codons 41-42, a G-C transition at position 5 of IVS-1, A-G transition at codon 19, an A-T transition at codon 17, an A-G transition at position -28 upstream of the beta globin gene, a G-T transition at position 1 of IVS-1), accounted for 92%. The spectrum of beta thalassemia mutations in Chinese Thai is similar to that reported among the Chinese from other parts of the world. The distribution of beta thalassemia mutations in Muslim Thai is similar to that reported among Malaysians. The most common beta thalassemia mutation in Thai and Chinese Thai patients is the frameshift mutation at codons 41-42, in comparison with the Muslim Thai in whom the G-C transition at position 5 of the IVS-1 mutation predominates. The heterogeneity of molecular defects causing beta thalassemia should aid in the planning of a prenatal diagnosis program for beta thalassemia in the South of Thailand.

Alleles↗
PubMed1995

Genetic heterogeneity of beta-thalassemia in southeast Sicily.

In this study we have defined the spectrum of the beta-thalassemia mutations, the beta-thalassemia haplotypes, and the genotype-to-phenotype correlations in a large number of patients with different beta-thalassemia conditions. Seventeen different beta-thalassemia mutations were detected which included one chromosome each with Hb Dhonburi and Hb Lepore. Five alleles, namely, codon 39 (C-->T), IVS-I-110 (G-->A), IVS-I-6 (T-->C), IVS-II-745 (C-->G), and IVS-I-1 (G-->A), account for 90% of all beta-thalassemia mutations in 846 thalassemic chromosomes studied. Haplotyping for a large number of subjects showed that the five common mutations are linked to a few haplotypes. The presence of milder mutations, mainly IVS-I-6 (T C), in about 19% of our patients explains some of the clinical variables. Among the 37 patients with thalassemia of intermediate severity, only 6 were homozygous or compound heterozygous for two severe alleles. The type of beta-thalassemia is the main factor responsible for differences in the phenotypic expression of the disease in patients with Hb S-beta-thalassemia; patients with Hb S-beta(+)-thalassemia are less severely affected than those with Hb S-beta(0)-thalassemia. The five most frequent mutations have comparable distributions all over Sicily.

Fetal Hemoglobin↗
PubMedDate not supplied

Impact of beta globin gene mutations on the clinical phenotype of beta thalassemia in India.

The beta thalassemias are one of the commonest group of autosomal recessive disorders in India. Although majority of patients are severe and transfusion-dependent, about 10-15% of cases have a milder phenotype. We evaluated the role of beta gene mutations in modulating the clinical presentation of 342 beta thalassemia patients which included 278 severe thalassemia major (TM) and 64 thalassemia intermedia (TI) cases (severe TI: 27; mild TI: 37) from this region. Thirteen beta thalassemia mutations were characterized by reverse dot blot hybridization or amplification refractory mutation system (ARMS); denaturing gradient gel electrophoresis (DGGE) analysis and DNA sequencing helped to characterize the remaining nine mutations. Majority of the patients in the thalassemia major and thalassemia intermedia groups had severe beta+ or beta0 mutations. IVS 1-5 (G-->C) was the commonest mutation in the three groups. The six severe and common Indian mutations [(IVS 1-5 (G-->C), 619 bp deletion, IVS 1-1 (G-->T), codons 8/9 (+G), codon 15 (G-->A), codons 41/42 (-CTTT)] accounted for 92.0% of molecular lesions in the thalassemia major group, 86.8% in the severe TI group, and 72.9% in the mild TI group. IVS 1-1 (G-->T) and codon 30 (G-->C) were significantly more common in thalassemia intermedia cases. The mild capsite +1 (A-->C) mutation was present in both severe and mild cases. Three other mild beta+ mutations, poly A (T-->C), -28 (A-->G), and -88 (C-->T), were seen only in the thalassemia intermedia cases. These four mild mutations in combination with other severe beta+ or beta0 mutations resulted in a very variable clinical presentation. This study reveals that, in majority of Indian patients, the beta genotype cannot predict the phenotype.

Blood Transfusion↗
PubMed2003

Alpha Thalassemia is associated with decreased risk of abnormal transcranial Doppler ultrasonography in children with sickle cell anemia.

PURPOSE: Cerebrovascular complications of sickle cell disease (SCD) are common, but the risk factors remain unclear. The multicenter Stroke Prevention Trial in Sickle Cell Anemia (STOP) provided an opportunity to examine alpha thalassemia-2 as a modifying risk factor, using abnormal transcranial Doppler ultrasonography (TCD) as a surrogate marker for cerebrovascular disease. The authors hypothesized that children with abnormal TCD are less likely to have alpha thalassemia-2, and an increased hemoglobin level accounts for this protective effect. METHODS: A retrospective study was conducted of children with SCD who had both alpha gene and TCD data from STOP: 128 with TCD of at least 200 cm/s (abnormal TCD) and 172 with TCD less than 170 cm/s (normal TCD). RESULTS: Alpha thalassemia-2 was more frequent in the normal TCD group compared with the abnormal TCD group. The odds ratio for normal TCD and alpha thalassemia-2 was 4.1. Adjusting for either hemoglobin level or red cell size (mean corpuscular volume) reduced the odds ratio only slightly. Age, normal TCD, and alpha thalassemia-2 had significant statistical interaction, so that alpha thalassemia-2 was not related to TCD for age 10 years or older. CONCLUSIONS: The frequency of alpha thalassemia-2 was significantly higher in children with normal TCD. Speculation on mechanisms of effect includes improved erythrocyte deformability, reduced red cell adhesion, and reduced nitric oxide scavenging in alpha thalassemia-2. The association of alpha thalassemia-2 and normal TCD adds to the evidence on the protective effects of alpha thalassemia-2 in SCD and highlights the contribution of epistatic factors.

Anemia, Sickle Cell↗
PubMed1981

Clinical and hematological evaluation of two delta 0 beta 0-thalassemia homozygotes.

Two homozygous delta 0 beta 0-thalassemia patients, one with the G gamma A gamma type and the other with the G gamma type, and their heterozygous parents are described. Red cell indices among the heterozygotes with the G gamma A gamma type of delta 0 beta 0-thalassemia were markedly different from those in heterozygotes with the G gamma type. However, the imbalance in in vitro hemoglobin synthesis was quite similar in the two heterozygous conditions. The same was observed for the homozygous patients; the in vitro chain synthesis was severely imbalanced as seen in beta-thalassemia major. The clinical and some of the hematological findings were milder in the G gamma-delta 0 beta 0-thalassemia homozygote than in the G gamma A gamma-delta 0 beta 0-thalassemia homozygote. The death of a sibling of the G gamma-delta 0 beta 0-thalassemia homozygote with a diagnosis of thalassemia major suggests that both types of delta 0 beta 0-thalassemia could follow a severe clinical and hematological course. The discovery of the G gamma type of delta 0 beta 0-thalassemia in a Turkish child shows that two types of delta 0 beta 0-thalassemia can be found in that country. Differentiation between the two types can only be made through structural analyses of Hb F.

Child↗
PubMedDate not supplied

Prevention of beta-thalassemia major by antenatal screening in Hong Kong.

The thalassemias are common in Hong Kong. One of the severe forms, beta-thalassemia major, has been preventable locally by antenatal screening since 1983. Yet new patients are still being diagnosed. In this retrospective study, 34 children with severe beta-thalassemia syndromes were diagnosed in two major public hospitals between 1990 and 1996. They included one pair of identical twins and two pairs of siblings. Twenty-seven (79%) had homozygous beta-thalassemia and seven (21%) had beta E thalassemia. All but four (12%) were transfusion dependent. Fifty-five (89%) parents had been evaluated for their thalassemia status. Forty-eight had beta-thalassemia traits and seven were hemoglobin E carriers. The reasons for the birth of these children with severe beta-thalassemia syndromes were (1) late or no antenatal visit (n = 8, 24.2%), including three cross-border deliveries in which the pregnant mothers came from mainland China to Hong Kong for confinement, (2) lack of maternal screening (n = 13, 39.4%), (3) lack of paternal screening (n = 7, 21.2%), (4) parental refusal (n = 3, 9.1%), and (5) unknown (n = 2, 6.1%). These findings suggest that several factors undermine the effectiveness of antenatal screening for prevention of thalassemias. Many medical practitioners and the general public are still not aware of the screening procedures. The migration of population from mainland China to Hong Kong may result in the birth of many more children with beta-thalassemia major.

Female↗
PubMed2000

Laboratory investigation of hemoglobinopathies and thalassemias: review and update.

Structural hemoglobin (Hb) variants typically are based on a point mutation in a globin gene that produce a single amino acid substitution in a globin chain. Although most are of limited clinical significance, a few important subtypes have been identified with some frequency. Homozygous Hb C and Hb S (sickle cell disease) produce significant clinical manifestations, whereas Hb E and Hb D homozygotes may be mildly symptomatic. Although heterozygotes for these variants are typically asymptomatic, diagnosis may be important for genetic counseling. Thalassemia, in contrast, results from quantitative reductions in globin chain synthesis. Those with diminished beta-globin chains are termed beta-thalassemias, whereas those with decreased alpha-chain production are called alpha-thalassemias. Severity of clinical manifestations in these disorders relates to the amount of globin chain produced and the stability of residual chains present in excess. The thalassemia minor syndromes are characterized clinically by mild anemia with persistent microcytosis. Thalassemia intermedia (i.e., Hb H disease) is typified by a moderate, variably compensated hemolytic anemia that may present with clinical symptoms during a period of physiologic stress such as infection, pregnancy, or surgery. The thalassemia major syndromes produce severe, life-threatening anemia. alpha-Thalassemia major usually is incompatible with extrauterine life; beta-thalassemia major presents in infancy and requires life-long transfusion therapy and/or bone marrow transplantation for successful control of the disease. Double heterozygosity for certain structural variants and/or thalassemia syndromes may also lead to severe clinical disease. Several guidelines have been published that outline the required steps for hemoglobinopathy and thalassemia investigation. The availability of HPLC has streamlined many of these requirements, allowing an efficient stepwise diagnostic strategy for these complex disorders.

Chromatography, High Pressure Liquid↗
PubMed2003

Erythroid bone marrow activity and red cell hemoglobinization in iron sufficient beta-thalassemia heterozygotes as reflected by soluble transferrin receptor and reticulocyte hemoglobin in content. Correlation with genotypes and Hb A(2) levels.

BACKGROUND AND OBJECTIVES: Ferrokinetic studies and erythroid cell ultrastructural studies have indicated some degree of ineffective erythropoiesis in heterozygous beta-thalassemia, although a wide case-to-case variation was observed. In this study we applied rapid biochemical and hematologic measurements to assess erythroid marrow activity (sTfR) and reticulocyte hemoglobin content (CHr) in iron-sufficient individuals with heterozygous beta-thalassemia and investigated the correlation with the degree of globin polypeptide chain imbalance by comparing parameters between beta-thalassemia heterozygotes with genotypes of variable severity. DESIGN AND METHODS: We studied 57 iron-sufficient adults with heterozygous beta-thalassemia, divided into groups according to genotype: group A: beta(silent)-thalassemia heterozygotes, group B: beta(+)-thalassemia heterozygotes and group C: beta(0)-thalassemia heterozygotes. Twenty-one hematologically normal individuals served as controls (group D). We measured hematologic parameters including CHr with a Bayer-Advia 120 hematology analyzer. Hemoglobins were analyzed by high performance liquid chromatography, while biochemical parameters of iron status (iron, ferritin, transferrin and sTfR) were measured with chemical, luminometric and nephelometric methods. RESULTS: We found significant positive correlations between sTfR values for all beta-thalassemia heterozygote groups when plotted against Hb A(2) and Hb F levels (r=0.566, p<0.0001 and r=0.283, p<0.03, respectively) and significantly negative correlation between CHr and Hb A(2) values (r=-0.790, p<0.00001). These data reflect the fine association of globin polypeptide chain imbalance with erythron expansion and the greater degree of ineffective erythropoiesis in beta-thalassemia heterozygotes with more severe genotypes. INTERPRETATION AND CONCLUSIONS: This study is the first demonstration that sTfR and CHr are useful parameters for evaluating the relative severity of different genotypes in heterozygous beta-thalassemia.

Adolescent↗
PubMed2004

Prevention and control of thalassemia at Saraburi Regional Hospital.

OBJECTIVE: To evaluate the program in prevention and control of thalssemia among pregnant women and their spouses, prevention of new cases by screening tests, confirmatory test, genetic counselling, prenatal diagnosis, and selective abortion. SUBJECTS: The pregnant women, attending antenatal care unit, Saraburi center hospital, as well as their spouses. 1 January 2000-31 December 2001 METHOD: As part of the antenatal care assessment, pregnant women before 16 weeks gestation were screened, with pre- and post-test counselling, by osmotic fragility (OF) and dichorophenol indophenol precipitate (DCIP) tests, and confirmed by complete blood count (CBC), mean corpuscular volume (MCV), hemoglobin typing and polymerase chain reaction for alphathal1 (PCR alphathal1) if any of two screening tests was positive. The husbands of those who were carriers of severe thalassemia were encouraged to have thalassemia screening and confirmation. When both the pregnant women and their husbands were carriers of severe thalassemia, the pregnant women would voluntarily perform the prenatal diagnosis. Termination of pregnancy would be offered when the fetus had severe thalassemia. RESULTS: There were 3,739 from 4,214 women (88.7% of all antenatal women), who participated in the program. OF and/or DCIP were positive in 1,742 of 3,739 subjects (46.5%). Of those, 960 from 1,742 (55.1%), had husbands who were willing to have the testing, and OF and/or DCIP were positive in 443 of 960 cases (46.1%). The confirmatory tests revealed carrier and disease of thalassemia, and hemoglobinopathies in 931 of 1,742 women (53.9%), and 135 of 960 husbands (14.0%). The 20 couples who had the possibility of having severe thalassemic newborns, were strongly advised to have prenatal diagnosis. The 12 risk pregnancies had been performed cordocentesis. Finally 3 of 12 (25.0%) fetuses were documented to have severe thalassemia and all of them decided to have selective abortion. CONCLUSIONS: The screening model for thalassemia carriers by using the combination of OF and DCIP is the easy screening model. It can be done quickly, it is inexpensive, therefore it is suitable for large numbers of population screening. The systematic screening, confirmatory of thalassemia diagnosis and prenatal diagnosis are the measure of thalassemia prevention and control, and aims to decrease the number of newborns with severe thalassemia.

Abortion, Eugenic↗
PubMed2006

Thalassemia among blood donors at the Hospital Universiti Sains Malaysia.

The aim of this study was to screen and identify the types of thalassemia among blood donors at the Hospital Universiti Sains Malaysia (HUSM). Thalassemia screening was performed by hemoglobin electrophoresis. A total number of 80 blood samples were obtained from donors at the Transfusion Medicine Unit, HUSM. The ethnic origins of the donors were Malays (n=73, 91.3%) and non-Malays (n=7, 8.75%). Males comprised 88.1% of the donors. Thalassemia was detected in 16.25% (n=13) of the blood donors. Of those with thalassemia, 46.2% (6/13) were anemic. Microcytosis and hypochromia were detected in 84.6% (n=l1) and 84.6% (n=l1) of these donors, respectively. The types of thalassemias detected were Hb E, 11.25% (n=9/80) and beta thalassemia trait, 5% (n=4/80). Among the thalassemias detected, the Hb E hemoglobinopathy was comprised of Hb E/ alpha-thalassemia (38.5%: n=5), Hb E /beta-thalassemia (23.1%: n=3), Hb E trait (7.6%: n=1) and beta-thalassemia (30.8%: n=4). In conclusion, screening for thalassemia trait should be included as part of a standard blood testing before blood donation. Further studies are required to look at the effects of donated thalassemic blood.

Blood Donors↗
PubMed1992

Characterization and comparison of the red blood cell membrane damage in severe human alpha- and beta-thalassemia.

The aim of the present work was to understand the pathophysiology of the severe human thalassemias as represented by beta-thalassemia intermedia and hemoglobin (Hb) H (alpha-thalassemia) disease. We have previously shown that the material properties of the red blood cell (RBC) and its membrane differ in severe alpha- and beta-thalassemia, and we now show that this difference is probably caused by accumulation of alpha-globin chains at the cytoskeleton in beta-thalassemia, whereas beta-globin chains are associated with the cytoskeleton in alpha-thalassemia. In both alpha- and beta-thalassemia, some of these globin chains have become oxidized as evidenced by loss of the free thiols. Furthermore, there is similar evidence of oxidation of protein 4.1 in beta-thalassemia, whereas beta-spectrin appears to be subject to oxidation in alpha-thalassemia. These observations support the idea that the association of partly oxidized globin chains with the cytoskeleton results in oxidation of adjacent skeletal proteins. The abnormality of protein 4.1 in beta-thalassemia is consistent with a prior observation, and is also in accord with the known importance of protein 4.1 in maintenance of membrane stability, a property that is abnormal in beta-thalassemic membranes.

Blotting, Western↗
PubMed1994

Rapid detection of deletions causing delta beta thalassemia and hereditary persistence of fetal hemoglobin by enzymatic amplification.

A considerable number of deletions of variable size and position that involve the beta-globin gene complex on chromosome 11 are associated with the clinical entities of hereditary persistence of fetal hemoglobin (HPFH) and delta beta thalassemia. Specific deletions appear to be associated with consistent phenotypes and some are known to be recurrent. To facilitate the molecular diagnosis of uncharacterized patients with HPFH and delta beta thalassemia, oligonucleotide primers have been designed to enzymatically amplify deletion-specific products for nine known deletions, which include those responsible for HPFH-1, HPFH-2, HPFH-3, Spanish (delta beta)zero thalassemia, hemoglobin (Hb) Lepore, Sicilian (delta beta)zero thalassemia, Chinese G gamma(A gamma delta beta)zero thalassemia, Asian-Indian inversion-deletion G gamma(A gamma delta beta)zero thalassemia, and Turkish inversion-deletion (delta beta)zero thalassemia. Using this approach, we have successfully characterized the molecular basis for delta beta thalassemia in 23 individuals from 16 families of diverse ethnic origins. Thirteen individuals from this group were shown to be heterozygous for the 13.4-kb Sicilian deletion, two were heterozygous for the 100-kb Chinese G gamma(A gamma delta beta)zero deletion, four were heterozygous for the Turkish form of inversion-deletion delta beta thalassemia, and three were heterozygous for the Asian-Indian form of inversion-deletion G gamma(A gamma delta beta)zero thalassemia. One Vietnamese subject was heterozygous for a 12.6-kb deletion, which we have fully characterized at the molecular level. Sequence analysis of the breakpoint regions of the Chinese deletion and the Turkish rearrangement indicates that, in each case, the mutation is likely to have arisen from a single origin. This hypothesis is supported by the evident geographical clustering of the various deletions described here.

Adult↗
PubMed1995

Molecular mechanisms of thalassemia in southeast Asia.

Hemoglobinopathies are the most common genetic disorders in Southeast Asia. alpha-Thalassemia is most often due to a alpha-globin gene deletion. Hb Constant Spring (CS) occurs from the mutation at the termination codon of the alpha-globin gene resulting in an elongated polypeptide; alpha(CS)-globin mRNA is also unstable and only small amounts of Hb CS are produced. Thus Hb CS has an alpha-thalassemia 2-like effect. beta-Thalassemia results from a variety of molecular mechanisms, most of which are single base substitutions or deletions or insertions of one to four nucleotides. Hemoglobin E occurs from a Glu --> Lys substitution at position 26 of the beta-globin chain. The abnormal gene also results in reduced amounts of beta E-mRNA and hence of beta E-globin chains. Therefore, Hb E has a mild beta + thalassemia phenotype. Homozygous beta-thalassemia and beta-thalassemia/Hb E are the major beta-thalassemic syndromes in Southeast Asia. In spite of seemingly identical genotypes, severity of beta-thalassemia/Hb E patients can vary greatly. Some may have a severe clinical disorder approaching that seen in homozygous beta-thalassemia. A number of genetic factors have been shown to determine the differences in severity of anemia in beta-thalassemia/Hb E, including co-inheritance of alpha-thalassemia determinants and co-inheritance of other determinants which elevate Hb F expression. A correlation between the extent of beta E-globin mRNA cryptic splicing and the severity of anemia in beta(zero)-thalassemia/Hb E patients has been observed. Complete characterization of mutations causing hemoglobinopathies will help to bolster the establishment of prenatal diagnosis of these genetic disorders in the region.

Alternative Splicing↗
PubMed1995

Prenatal diagnosis for beta-thalassemia syndromes using HRP-labeled oligonucleotide probes at Siriraj Hospital.

Characterization of the molecular defect of beta-thalassemia in Thais has enabled us to establish prenatal diagnosis for homozygous beta-thalassemia and beta-thalassemia/Hb E. The nature of the beta-thalassemia mutation of each high risk couple or of the previous affected child was firstly identified after counseling. Detection of beta-thalassemia mutations was performed by dot-blot hybridization of the amplified DNA with a set of HRP-labeled ASO-probes specific for the common mutations. If the mutation could be characterized, prenatal diagnosis (PND) would be performed by using DNA extracted either from the chorionic villi (CVS) or amniotic fluid fibroblast in the first trimester of pregnancy or from fetal blood in the second trimester. DNA analysis was carried out in 23 couples at risk of having homozygous beta-thalassemia and 88 couples at risk for beta-thalassemia/Hb E. However, PND was performed by this technique in 22 pregnancies from 21 couples at risk of having homozygous beta-thalassemia children and 86 pregnancies from 71 couples at risk for beta-thalassemia/Hb E; 9 couples underwent more than one prenatal diagnosis. The results showed that, although there are more than 20 beta-thalassemia mutations in the Thai population, PND by DNA analysis could be carried out in more than 95% of the risk couples by using beta(E) and 10 different HRP-labeled ASO probes. This technique was simple, economic and avoided the use of radioactive isotope.

Amniocentesis↗
PubMed1997

[Molecular diagnosis of beta-thalassemia intermedia].

OBJECTIVES: To analyze the molecular abnormalities of beta-thalassemia intermedia and contribute to the knowledge of the molecular diagnosis and prenatal diagnosis of this disorder. METHODS: In 14 patients with beta-thalassemia intermedia, we analyzed the hematologies, alpha, beta and gamma globin gene organization and structure as well as globin gene biosynthesis by Southern blot hybridization, multiplex allale specific PCR (MAS-PCR), DNA sequencing and micro-globin chain biosynthetic assay. Moreover, alpha globin gene organization was studied in 250 cord blood specimens. RESULTS: Of the 14 patients, 4 were found to be beta-thalassemia heterozygotes combined with rightward cross-over or/and leftward cross-over triplicated haplotype of alpha-globin gene loci (alpha alpha alpha anti3.7 or/and alpha alpha alpha anti4.2), 3 were compound heterozygotes for beta-thalassemia combined with alpha-thalassemia 1 or 2, one was identified to be a compound heterozygote for beta-thalassemia combined with G gamma promotor-158 (C-->T) mutation. The data of the alpha globin gene organization in 250 cord blood specimens showed that 8 of the 500 tested chromosomes (1.6%) were abnormal: 3 were alpha alpha alpha anti3.7, 4 were alpha -3.7, and one was --SEA. CONCLUSION: In addition to beta-thalassemia homozygote or compound heterozygotes with alpha thalassemia, the conjunctive abnormalities of beta-thalassemia heterozygote with alpha-globin gene triplication was another major cause of beta-thalassemia intermedia.

Adolescent↗
PubMed2007

Prevalence of thalassemia in patients with microcytosis referred for hemoglobinopathy investigation in Ontario: a prospective cohort study.

In Ontario, Canada, beta-thalassemia is easily detected through measurement of hemoglobin A2, but most laboratories do not do exhaustive DNA investigations for alpha-thalassemia. Therefore, the prevalence of thalassemia in microcytic samples for hemoglobinopathy investigation in Ontario is unknown. To address this, we performed a prospective cohort study in which samples referred for hemoglobinopathy investigation were also evaluated for alpha-thalassemia by DNA testing. Of 800 samples submitted, 664 were evaluable. Of the 664 patients represented, 163 (24.5%) were beta-thalassemia major carriers, 68 (10.2%) were hemoglobin Bart's hydrops fetalis carriers and, in total, 361 (54.4%) had some form of thalassemia. We conclude that microcytosis due to thalassemia is common in Ontario and that major forms of thalassemia, including forms predisposing to hemoglobin Bart's hydrops fetalis and beta-thalassemia major, are frequent. This illustrates the importance of adequate prenatal and laboratory investigation for these abnormalities in Ontario and other similar multiethnic jurisdictions worldwide.

Adolescent↗