The Spectrum of beta-Thalassemia Mutations in the Arab Populations

Folate deficiency is associated with nutritional anaemia in Lebanese women of childbearing age

OBJECTIVE

The objective of this study was to identify the determinants of anaemia in Lebanese women of childbearing age attending health centres in Lebanon.

DESIGN

Cross-sectional study carried out between May and December 2003. Anthropometric measurements as well as sociodemographic, health and dietary intake data were collected using a questionnaire. Haemoglobin (Hb), plasma ferritin, plasma folate and vitamin B12 were assessed using standard laboratory methods.

SETTING

Governmental health centres in Lebanon.

SUBJECTS

Four hundred and seventy non-pregnant Lebanese women aged 15-45 years.

RESULTS

Anaemia (Hb <12 g dl(-1)) and iron deficiency (ferritin <15 microg l(-1)) were prevalent in 16.0 and 27.2% of the study sample, respectively. Of the total sample, 7.7% had iron-deficiency anaemia. The percentage of women with either Hb or ferritin deficiency or both was 35.6%. Plasma folate and vitamin B12 deficiency was reported in 25.1 and 39.4%, respectively, and 12.6% of the women had both folate and vitamin B12 deficiencies. Of the anaemic group, 48.0% of the women had iron deficiency. The intake of iron was lower in iron-deficient than in non-deficient women and a positive relationship was shown between folate intake and its corresponding serum levels. Regression analysis showed that ferritin, plasma folate and family history of anaemia were significant determinants of the anaemia in the sample of women.

CONCLUSIONS

Anaemia not related to iron deficiency was partly explained by plasma folate deficiency. Measures to control folate and iron deficiency should be considered.

Molecular characterization of beta-thalassemia in the Dohuk region of Iraq

beta-Thalassemia (thal) is an important health problem in the Dohuk region of northern Iraq because of its high carrier rate and the frequency of consanguineous marriages. Thus, the need to establish an effective preventative program is paramount. As part of this effort, we initiated this study to determine the molecular basis of this disorder in the region. For the latter purpose, either parent of 104 registered beta-thal major/intermedia patients had their full blood counts, hemoglobin (Hb) electrophoresis, Hb A2 and Hb F quantitation performed. Their DNA was extracted, amplified and reverse hybridized to specific oligonucleotide probes to detect 20 beta-thal mutations. The testing detected 12 beta-thalassemic mutations. The eight most frequent were: IVS-II-1 (G-->A), codon 44 (-C), codon 5 (-CT), IVS-I-1 (G-->A), codon 39 (C-->T), IVS-I-6 (T-->C), codons 8/9 (+G) and IVS-I-5 (G-->C). These mutations accounted for 81.7% of the thalassemic defects in the studied individuals. The less frequent mutations were: codon 8 (-AA), IVS-I-110 (G-->A), codon 30 (G-->C) and codon 22 (-7 bp), and the beta-thalassemic defects remained uncharacterized in 11.5% of cases. This is the first study of beta-thal mutations from Iraq, and shows a frequency of thalassemic defects different from those reported in surrounding countries. It provides a foundation for prenatal genetic testing that will be part of a thalassemia prevention program in the Dohuk region.

Beta-thalassemia: the Lebanese experience

Beta-thalassemia is a hereditary anemia that is quite prevalent in Lebanon. Most patients with beta-Thalassemia are treated and followed up mostly at a multidisciplinary center, located in the suburban area of Beirut: the Chronic Care Center (CCC), operational since 1994. We will review the experience with beta-Thalassemia accumulated through this institution. Four hundred and twenty five patients, aged 2 to 68 years are followed up at the CCC. Sixty four percent have thalassemia major (TM) while 36% have thalassemia intermedia (TI). Lebanese patients with TM receive periodic packed red cell transfusions to maintain a pre-transfusional hemoglobin level of 10 gm/dl at all times and desferrioxamine is the standard iron chelator in use. Since 1994, 12 patients with TM have died from complications of their disease, with heart failure being responsible for the majority of deaths. The incidence of cardiac, endocrinologic, and infectious complications will be reviewed. Finally, both current and prospective preventive measures will be discussed, specifically educational campaigns and premarital screening. The effects of prevention are starting to show as the number of newly diagnosed disease is diminishing.

Genetic diversity among the Arabs

The Arabs in general are genetically diverse. Major factors that contributed to their diversity include the migrations of Semitic tribes from the Arabian Peninsula, the Islamic expansion in the 7th century AD, the Crusade wars and the recent migration dynamics. These events have resulted in the admixture of the original Arabs with other populations extending from east and south Asia to Europe and Africa. Their demographic features include high rates of consanguinity, a large family size and a rapid population growth. There is a high frequency of autosomal recessive disorders and increased frequencies of homozygosity for autosomal dominant traits, such as familial hypercholesterolemia and X-linked traits, such as glucose-6-phosphate dehydrogenase deficiency. The patterns of autosomal recessive disorders, including their mutations, may be different in various geographic locations within the Arab world. However, there are disorders that are specifically prevalent among the Arabs either uniformly or in certain locations. The Arab Genetic diseases include Bardet-Biedl syndrome, Meckel syndrome, autosomal recessive severe childhood muscular dystrophy, osteopetrosis and renal tubular acidosis, Sanjad-Sakati syndrome and others.

Clinical and molecular aspects of haemoglobinopathies in Tunisia

BACKGROUND

For the last two decades, studies on the population genetics of Tunisians have focused on variations of protein and genetic markers. Results confirmed the genetic heterogeneity of Tunisians caused by the admixtures with migratory human groups arriving mainly from Africa, Europe, and Asia. These studies also allowed the screening of rare mutants and many haemoglobin variants.

METHODS

The present study delineates the incidence of the different haemoglobinopathies in Tunisia. Previously collected data and results obtained from epidemiological and clinical studies of 1238 blood donors and 276 patients were compared. The chromosomal backgrounds of different haemoglobinopathies were explored by molecular techniques (denaturing gradient gel electrophoresis (DGGE), amplification refractory mutation system (ARMS) polymerase chain reaction (PCR), and sequencing).

RESULTS

This study indicates that appropriate DNA methodologies required for a nationwide preventive program in Tunisia are available and that prenatal diagnosis is feasible. Additionally, analysis of sequence polymorphisms allowed a better understanding of the gene recombination events and their application for tracing back the origin and the diffusion of the mutations.

CONCLUSIONS

Molecular analysis techniques such as DGGE and ARMS PCR are socially and economically the most suitable techniques to be used in Tunisia for the detection and the identification of haemoglobin abnormalities. At present, their use is essential to conduct a clear and efficient screening program.

Abnormal glucose tolerance in Egyptian beta-thalassemic patients: possible association with genotyping

BACKGROUND

Type 1 diabetes mellitus (DM) is a frequent complication in patients with beta-thalassemia. It is believed to be due to the damage inflicted by iron overload of the pancreatic beta cells. Liver disorders and genetic influences seem to be additional predisposing factors.

OBJECTIVE

To study the prevalence of diabetes and impaired glucose tolerance (IGT) in transfusion-dependent Egyptian beta-thalassemic patients and to evaluate the possible role of genotyping in the pathogenesis of diabetes associated with beta-thalassemia.

RESEARCH DESIGN AND METHODS

A total of 56 transfusion-dependent beta-thalassemic patients aged 10-31 (mean age=15.9 +/- 5.7 yr), 32 males and 24 females, including 48 thalassemia major and eight thalassemia intermedia; compared to 15 age- and sex-matched controls. All were subjected to history and examination, laboratory investigations: complete blood count (CBC), serum ferritin, liver function tests, hepatitis B and C markers, fasting blood glucose, oral glucose tolerance test (OGTT) and fasting C-peptide. Genotyping for 16 mutations was assessed in thalassemic patients with abnormal glucose tolerance.

RESULTS

The prevalence of diabetes was 10.4% (5 of 48) and IGT was 14.6% (7 of 48) among thalassemia major, whereas, none of thalassemia intermedia had abnormal glucose tolerance. Fasting C-peptide was lower in beta-thalassemic patients compared to controls (p <0.001); the level was significantly higher in patients complicated by diabetes or IGT compared with other thalassemic patients (p <0.001). Chronic hepatitis C was detected in all patients (100%) with abnormal glucose tolerance. Genotyping showed that IVS II nt 745 was detected in 77.7% of cases with abnormal glucose tolerance.

CONCLUSIONS

Abnormal glucose tolerance is common in multiply transfused beta-thalassemia major patients, which could be attributed to progressive and early loss of beta-cell mass, along with persistent insulin resistance. Chronic hepatitis C may play a role in the development of abnormal glucose tolerance. An association between diabetes and genotyping IVS II nt 745 was found. Patients with this particular genotype are advised to check their blood glucose every 6 months to detect early occurrence of diabetes.

Rapid detection of beta-globin gene mutations and polymorphisms by temporal temperature gradient gel electrophoresis

BACKGROUND

Inherited hemoglobin disorders represent the most common Mendelian disease worldwide. Prevention programs based on molecular diagnosis of heterozygous carriers and/or patients require the use of reliable mutation scanning methods in at-risk populations.

METHODS

We developed a rapid and highly specific mutation-screening test based on temporal temperature gradient gel electrophoresis (TTGE). We analyzed 889 beta-thalassemia genes from homozygous beta-thalassemia patients and unrelated individuals with heterozygous beta-thalassemia. Previously reported common mutations were screened by reverse dot blots using allele-specific probes. The rare mutations were analyzed by TTGE.

RESULTS

We found common mutations in 753 beta-thalassemia genes. TTGE analysis in the rest of the genes showed the presence of mutations in different regions of the beta-globin gene in 134 of them, and these mutations were characterized by DNA sequencing. In the two genes in which mutations were not identified, large deletions spanning beta-globin gene were suspected.

CONCLUSIONS

Compared with other approaches for comprehensive mutation screening, the reported method is rapid, highly sensitive, cost-effective, and suitable for high-throughput screening of a large number of samples.