A Family With a Hemoglobin E Variant Including a Thai Immigrant Woman in Korea

No abstract available.

Hemoglobin E disorder: Newborn screening program.

Hemoglobin E (Hb E) disorder is an important kind of hemoglobinopathy. It can be seen around the world with the highest prevalence in Southeast Asia. The screening for this disorder becomes the public health policies in many countries. The screening can be performed in several population groups. The newborn screening program for Hb E disorder is an important issue in pediatric genetics. In this brief review, the author discusses on important laboratory tests for screening for Hb E disorder in newborn.

Hb E/beta-thalassaemia: a common & clinically diverse disorder.

Haemoglobin E-beta thalassaemia (Hb E/β-thalassaemia) is the genotype responsible for approximately one-half of all severe beta-thalassaemia worldwide. The disorder is characterized by marked clinical variability, ranging from a mild and asymptomatic anaemia to a life-threatening disorder requiring transfusions from infancy. The phenotypic variability of Hb E/β-thalassaemia and the paucity of long-term clinical data, present challenges in providing definitive recommendations for the optimal management of patients. Genetic factors influencing the severity of this disorder include the type of beta-thalassaemia mutation, the co-inheritance of alpha-thalassaemia, and polymorphisms associated with increased production of foetal haemoglobin. Other factors, including a variable increase in serum erythropoietin in response to anaemia, previous or ongoing infection with malaria, previous splenectomy and other environmental influences, may be involved. The remarkable variation, and the instability, of the clinical phenotype of Hb E beta-thalassaemia suggests that careful tailoring of treatment is required for each patient, and that therapeutic approaches should be re-assessed over-time.

Haemoglobinopathies in Southeast Asia.

In Southeast Asia α-thalassaemia, β-thalassaemia, haemoglobin (Hb) E and Hb Constant Spring (CS) are prevalent. The abnormal genes in different combinations lead to over 60 different thalassaemia syndromes, making Southeast Asia the locality with the most complex thalassaemia genotypes. The four major thalassaemic diseases are Hb Bart's hydrops fetalis (homozygous α-thalassaemia 1), homozygous β-thalassaemia, β-thalassaemia/Hb E and Hb H diseases. α-Thalassaemia, most often, occurs from gene deletions whereas point mutations and small deletions or insertions in the β-globin gene sequence are the major molecular defects responsible for most β-thalassaemias. Clinical manifestations of α-thalassaemia range from asymptomatic cases with normal findings to the totally lethal Hb Bart's hydrops fetalis syndrome. Homozygosity of β-thalassaemia results in a severe thalassaemic disease while the patients with compound heterozygosity, β-thalassaemia/Hb E, present variable severity of anaemia, and some can be as severe as homozygous β-thalassaemia. Concomitant inheritance of α-thalassaemia and increased production of Hb F are responsible for mild clinical phenotypes in some patients. However, there are still some unknown factors that can modulate disease severity in both α- and β-thalassaemias. Therefore, it is possible to set a strategy for prevention and control of thalassaemia, which includes population screening for heterozygotes, genetic counselling and foetal diagnosis with selective abortion of affected pregnancies.

Hemoglobin E disorders in Eastern Uttar Pradesh.

The distribution of hemoglobin E (alpha2beta2 26Glu (R)Lys ) is mostly restricted to Northeastern India. While evaluating the patients of jaundice, we came across two cases of hemoglobin E (Hb E) disorders. The first case is in a 22-year-old Bengali male and the second case of Hb E/beta thalassemia in a 5-year-old Hindu boy. The family study revealed Hb E trait in both the parents of Case 1, whereas in Case 2, the father was found to have Hb E trait and the mother had beta -thalassemia minor, thus confirming the diagnosis. Herein, we present the laboratory diagnosis and comparative data of the spectrum of Hb E disorders (i.e., heterozygous Hb E trait, homozygous Hb E disease and compound heterozygous Hb E/beta -thalassemia) that was found in our index cases and their parents.

Hemoglobin E-thalassaemia in a Sikh child: a case report.

Hemoglobin E is a beta chain variant that has its most clinically significant interaction with thalassaemia. The compound heterozygous state, thus produced, can result in a thalassaemia intermedia/major phenotype with affected individuals being transfusion dependent. Hemoglobin E is very common in north-east India with relatively fewer reportsfrom rest of the country. Reports of hemoglobin E in the Punjabi population are even rarer. A case of hemoglobin E-thalassaemia in a Sikh child is being presented because of its highly uncommon occurrence in natives of Punjab.

Screening for haemoglobinopathies and G6PD deficiency among the Mizos of Mizoram: a preliminary study.

The population of North-eastern region of India is of different tribes, races and ethnic backgrounds. The study of abnormal haemoglobins and G6PD has been usefully utilized in population genetics to evaluate the nature and extent of selective forces operating in a population. Data on haemoglobinopathies and G6PD deficiency is still not available from the State of Mizoram. The present study was aimed to document the frequency of these genetic traits in the Mizos of Mizoram. Blood samples in the form of dried filter paper spots collected from 490 Mizos were subjected to haemoglobin electrophoresis in starch agar gel for detection of haemoglobin variants and fluorescent spot test was conducted for screening of G6PD deficiency. Hb E was the only haemoglobin variant detected. The prevalence of the carreer state was documented to be 1.5%. G6PD deficiency was prevalent in 17.5% of this population. The prevalence of Hb E was much lower and that of G-6PD deficiency was found to be much higher than what has been reported from most other states of the north-eastern region of India. This might point towards a different ethnic origin of this population.

Genetic variants of beta-globin gene in Thai malaria patients.

Hemoglobin E (E26K variant of beta-globin gene) causing hemoglobinopathy is commonly observed in parts of Thailand, regardless of the hematologic disadvantage of the homozygotes. In order to detect further variants of the beta-globin gene, we performed variation screening for exon 1 of the beta-globin gene in 64 adult patients with P. falciparum malaria, living in northwest Thailand. We identified E26K and two novel variants, 59C>T and IVS+1G>T. IVS+1G>T lies on the splice donor site, and a substitution of A for G at the same site (IVS+1G>A) is known to be linked to beta-thalassemia. Thus, the biological significance of IVS+1G>T and its association with malarial infection should be clarified in future studies.

Variable clinical severity of Hb E beta-thalassemia among Indians.

OBJECTIVE: The aim of this preliminary report was to look at the effect of genetic variations in the alpha, beta and gamma globin genes in 7 cases of hemoglobin E/beta-thalassemia with diverse clinical expression of the disease. METHODS: beta-thalassemia mutations were characterized by PCR and dot blot hybridization. G gamma gene polymorphism (Xmnl) was determined by PCR followed by restriction enzyme digestion and polyacrylamide gel electrophoresis. alpha genotyping was done by Southern blot hybridization. RESULTS: Six cases had a severe beta+ mutation [IVS 1 nt 5 (G-->C)] and one case had a beta zero mutation [F/S 41/42 (-CTTT)]. Hence, the beta-thalassemia mutation does not seem to contribute towards the clinical diversity. alpha-genotyping showed a single alpha-gene deletion of the rightward type in three of the five milder cases. The -158 G gamma (C-->T) substitution was present at least in heterozygous state (+/-) in all the milder cases. CONCLUSIONS: Deletional alpha thalassemia and presence of the -158 G gamma (C->T) substitution are the two factors which appear to be more important in decreasing the severity of the disease rather than the nature of the beta thalassemia mutation.

Hemoglobin E-beta thalassemia in Uttar Pradesh.

OBJECTIVE: To evaluate the molecular make up of hemoglobin E-Beta thalassemia to facilitate diagnosis, genetic counseling and prenatal diagnosis in Uttar Pradesh. DESIGN: DNA analysis. SETTING: Referred hemolytic anemia cases to Genetics OPD of a tertiary care center. SUBJECTS: 21 families of HbE-thalassemia of which 19 were of UP origin. METHODS: The patient and obligate carriers in their families were evaluated at hematological, biochemical and molecular level. A total of 62 cases were evaluated which included the index cases and their family members. Red blood cell indices, osmotic fragility, hemoglobin electrophoresis, quantitation of fetal hemoglobin, HbA2/E, serum iron and total iron binding capacity estimation were carried out in all the blood samples. DNA analysis was done for HbE and beta thalassemia mutations. RESULTS: The commonest, IVSI-5 (G-->C) mutation (57%) was found along with HbE mutation. Only 23/26 cases belonged to the group of common beta-thal mutations as described in literature. CONCLUSION: Establishment of antenatal diagnostic services is necessary in those parts of India where both these mutations are commonly seen.

Red cell parameters in alpha-thalassemia with and without beta-thalassemia trait or hemoglobin E trait.

Eighty-five patients who attended at Ramathibodi Hospital during November 1994 to June 1996 were investigated for thalassemia genotype, hemoglobin (Hb) typing and blood cell parameters. All patients were screened primarily for complete blood count using the Technicon H*3 automated hematology analyzer and Hb typing using the automated HPLC. Their genotypes were evaluated by in vitro gene amplification using primers for detection of common alpha-thalassemic genes found in the Thai population. We found 45 cases out of 85 were alpha-thalassemia trait with A2A typing, 10 were normal, 7 were alpha-thalassemia trait complicated by beta-thalassemia trait or HbE trait, 18 were HbH disease or HbH with Hb Constant Spring (HbH/CS), and 5 were AE Bart's disease. The alpha-thalassemia 1 trait had heterogeneity in red cell population as shown by increased red cell distribution width (RDW), the increased percent microcytic red cell (%Micro) and decreased mean cell volume (MCV). Red cell parameters in alpha-thalassemia 2 trait and HbCS trait were not significantly different from normal. The cases with coinheritance of alpha-thalassemia trait with beta-thalassemia trait or with HbE trait showed variation in their red cell parameters: one case showed less abnormal red cell parameters than those of uncomplicated alpha-thalassemia but the other two cases showed unimproved values. The homozygous alpha-thalassemia 2 showed similar red cell parameters to the alpha-thalassemia 1 trait. In conclusion, we can screen the alpha-thalassemia 1 trait and homozygous alpha-thalassemia 2 by using the simple red cell parameters such as the MCV and RDW; however, they must be confirmed for alpha-thalassemic genes. Unfortunately, red cell parameters of alpha-thalassemia 2 trait or HbCS trait were not different from those of normal subjects.

Molecular and hematological characterization of HbE heterozygote with alpha-thalassemia determinant.

Hemoglobin E and alpha-thalassemia are prevalent in Thailand. The chance that an individual heterozygous for HbE also carries an alpha-thalassemia determinant is high. In this individual, the amount of HbE and other hematological parameters may be differed from that of usual observation. In this study, a total of 132 HbE heterozygotes were screened for alpha-thalassemia 1 gene deletion by the polymerase chain reaction. Out of 132 cases, 71 could be completely analyzed for hematologic parameters. Forty-three of 88 cases with HbE less than 25% as measured using microcolumn chromatography were positive for this gene deletion. In twenty of these 43 alpha-thalassemia 1 positive cases, the average values of Hb, Hct, MCV, MCH, MCHC, RDW and HbE were 10.6 g/ dl, 33.1%, 64.8 fl, 21.0 pg, 32.3 pg/dl, 18.6% and 17.4%, respectively. Eight of 9 alpha-thalassemia 1 negative cases were positive for alpha-thalassemia 2 gene deletion in Southern blot analysis. In this later group, hematological parameters were similar to that of the former. Co-inheritance of the Hb Constant Spring gene has no direct effect on the level of HbE. No alpha-thalassemia 1 gene was detected in the remaining 34 cases whose HbE were above 25%. The average amount of Hb, Hct, MCV, MCH, MCHC, RDW and HbE were 12.4 g/dl, 37.7%, 79.7 fl, 26.2 pg, 32.7 pg/dl, 25.8% and 28.5%, respectively. Therefore, screening for HbE level below 25% may be a convenient way of identifying parents of carrying alpha-thalassemia 1 determinant.

Clinical, hematological and molecular features in Thais with beta-Malay/beta-thalassemia and beta-Malay/HbE.

A total of 50 patients and relatives were studied comprising 12 cases of compound heterozygosity of beta-Malay and beta + thalassemia, 10 cases of compound heterozygosity of beta-Malay and beta degree thalassemia, 10 cases of beta-Malay and HbE and 18 cases of beta-Malay heterozygosity. Patients with beta-Malay and HbE had very mild clinical symptoms or were asymptomatic of thalassemia disease in the absence of blood transfusion. Homozygosity of beta-Malay produce mild clinical symptoms of thalassemic disease with normal facial characteristics and were not transfusion dependent. Patients with beta-Malay and IVS 1 nt 5 (G-C) had severe clinical symptoms, and were transfusion dependent. Patients with beta-Malay and beta degree thalassemia had severe clinical symptoms, delayed weight and height in relation to age, were transfusion dependent and had classical features of thalassemic diseases.

The spectrum of beta-thalassemia mutations in Malays in Singapore and Kelantan.

The spectrum of beta-thalassemia mutations in Malays in Singapore and Kelantan (Northeast Malaysia) was studied. Allele specific priming was used to determine the mutations in beta-carriers at -28, Codon 17, IVSI #1, IVSI #5, Codon 41-42 and IVSII #654 along the beta-globin gene. The most common structural hemoglobin variant in Southeast Asia, Hb E, was detected by DNA amplification with restriction enzyme (Mnl1) analysis. Direct genomic sequencing was carried out to detect the beta-mutations uncharacterized by allele-specific priming. The most prevalent beta-mutations in Singaporean Malays were IVSI #5 (45.83%) followed by Hb E (20.83%), codon 15 (12.5%) and IVSI #1 and IVSII #654 at 4.17% each. In contrast, the distribution of the beta-mutations in Kelantan Malays differed, with Hb E as the most common mutation (39.29%) followed by IVSI #5 (17.86%), codon 41-42 (14.29%), codon 19 (10.71%) and codon 17 (3.57%). The beta-mutations in Kelantan Malays follow closely the distribution of beta-mutations in Thais and Malays of Southern Thailand and Malays of West Malaysia. The AAC-->AGC base substitution in codon 19 has been detected only in these populations. The spectrum of beta-mutations in the Singaporean Malays is more similar to those reported in Indonesia with the beta-mutation at codon 15 (TGG-->TAG) present in both populations. The characterization of beta-mutations in Singaporean and Kelantan Malays will facilitate the establishment of effective prenatal diagnosis programs for beta-thalassemia major in this ethnic group.

Genetic epidemiology of the three predominant abnormal hemoglobins in India.

Hemoglobinopathies in India are Important public health problems. Of the several abnormal of hemoglobin molecules, there are three variants, viz. Sickle cell, hemoglobin E and hemoglobin D which are predominantly prevalent in India. The cumulative gene frequencies of these hemoglobins have been found to be 5.35% in India. The average gene frequency of sickle cell and hemoglobin D in India has been observed to be 4.3% and 0.86%, respectively. In the North Eastern region of India, the gene frequency of hemoglobin E is 10.9%. Gene frequencies and spatial distribution of the predominant abnormal hemoglobins in India have been discussed in variance with the previous generalisations.

Role of alternatively spliced beta E-globin mRNA on clinical severity of beta-thalassemia/hemoglobin E disease.

In spite of seemingly identical genotypes, severity of beta-thalassemia/hemoglobin (Hb) E patients can vary greatly. Some may have a severe clinical disorder approaching that seen in homozygous beta-thalassemia. Since mutation in codon 26 of the beta E-globin gene can lead to an alternative splicing, Hb E acts like a mild beta(+)-thalassemia. Variation in the amount of beta E-globin mRNA may also govern the difference in severity of anemia in beta-thalassemia/Hb E patients who otherwise have the same genetic determinants. We have determined the percentage of the alternatively spliced beta E-globin mRNA by the RT-PCR technique in 14 patients and found that the amount of abnormal spliced beta E-globin mRNA in those patients with severe symptoms ranged between 2.9 to 6.1%, whereas those with milder symptoms had the values which ranged between 1.6 to 2.6%. The extent of beta E-globin mRNA cryptic splicing was better associated with clinical severity of the patients than did the patterns of the Xmn I polymorphism at position -158 of the G gamma-globin gene or levels of Hb F.

A simple non radioactive method for detecting beta-thalassemia/hbe disease: application to prenatal diagnosis.

We have developed allele specific polymerase chain reaction (ASPCR) that allows rapid screening of the beta E-globin and common beta-thalassemia genes in Thailand. These non-radioactive methods are based on the amplification by the polymerase chain reaction of the beta E and beta-thalassemia specific DNA fragments using specific primers. With this approach, both heterozygote and homozygote for the disease could readily be identified on agarose gel electrophoresis of the amplified DNA. We have applied the method for a prenatal diagnosis of beta-thalassemia/HbE disease in a Thai family at the second trimester of pregnancy. The result obtained was comparable to that of conventional dot blot hybridization using radioactive probes. The simplicity, accuracy and non isotopic of the approach make it a highly promising method for a carrier screening and a prenatal diagnosis of this common disorder.

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.

Menarcheal age in relation to ABO blood group phenotypes and haemoglobin-E genotypes.

The age at menarche in relation to ABO blood group phenotypes and haemoglobin-E genotypes has been studied among 290 girls belonging to Mongoloid ethnic stock in the North Eastern region of India. The study shows that the age at menarche is influenced by the abnormal haemoglobin E genotype as well as ABO blood group phenotype. Thus, the genetic markers play a pivotal role in the growth and development of an individual.