α-Thalassemia Mutations in Khuzestan Province, Southwest Iran

The worldwide molecular spectrum and distribution of thalassaemia: a systematic review

CONTEXT

Thalassaemia is one of the most common inherited autosomal recessive disorders around the world. A considerable amount of literature has been published about the type of mutations and the prevalence of thalassaemia, but findings are often contradictory.

OBJECTIVE

This systematic review aimed to provide a comprehensive view of the prevalence of thalassaemia-associated mutations in different countries, their effect on haemoglobin (Hb) levels, as well as reporting thalassaemia-associated rare mutations.

METHODS

A systematic search of the literature was carried out through major indexing databases (MEDLINE/PubMed, Scopus, EMBASE, Cochrane central, and ISI web of science) using keywords: "Co-inheritance, αα, β, thalassaemia" and "α-β thalassaemia, Mediterranean anemia, mutations" from 1998-September 2019. Hand-searching was also performed. There was no language restriction.

RESULTS

The initial searches yielded 1059 studies, of which 92 articles were included following inclusion and exclusion criteria. Of these, 3.3% (3) of articles were cohort studies, and 96.7% (89) of the remaining articles were cross-sectional studies. Our findings showed that 45.6% (42) of researchers investigated β-thalassaemia, 22.9% (21) αα-β thalassaemia, and 31.5% (29) α thalassaemia.

CONCLUSION

The present study provides valuable information about the spectrum of thalassaemia-associated mutations, which can be useful for preventing thalassaemia, reducing costs of care, reducing the treatment-related side effects, and showing the most defective mutations.HighlightEvaluating the increase or decrease in the birth prevalence of thalassaemiaIdentifying the most common and rare mutations in various parts of the worldComparing researchers' findings from various parts of the world.

α-Globin Genotypes Associated with Hb H Disease: A Report from Oman and a Review of the Literature from the Eastern Mediterranean Region

α-Thalassemia (α-thal) is the most common autosomal recessive hemoglobinopathy. There is a vast diversity and geographical variability in underlying genotypes in Hb H (β4) patients. Herein, we describe the genotypes found in the largest report of Omani Hb H patients. Moreover, we reviewed and summarized the literature published from the Eastern Mediterranean region. A retrospective review of all genetically confirmed Hb H disease patients diagnosed between 2007 and 2017 at Sultan Qaboos University Hospital, Muscat, Oman, was performed. Hematological parameters and clinical presentations were assessed. Both α-globin genes were screened for deletional and nondeletional mutations using a stepwise diagnostic strategy as described before. A total of 52 patients (27 females and 25 males) with a mean age of 20.6 years (range 0.23-80.0) were molecularly confirmed to carry Hb H disease. The patients had a hemoglobin (Hb) level of 9.3 g/dL (range 5.7-13.0) and mean corpuscular volume (MCV) of 58.4 fL (range 48.2-82.1). A total of eight genotype combinations were identified, with α2 polyadenylation signal mutation (polyA1) (AATAAA>AATAAG (α^PA1α/α^PA1α), often cited as α^T-Saudiα/α^T-Saudiα, being the most common (53.8%) followed by -α^3.7/- -^{MED I} (28.8%). Our cohort also included patients with combinations of α^PA1 with other Hb variants: α^PA1α/α^PA1α with Hb S (HBB: c.20A>T) trait (n = 2), -α^3.7/α^PA1α (n = 2) and α^{codon 19}α (HBA2: c.56delG)/α^PA1α (n = 1). Nondeletional Hb H disease due to the α^PA1 mutation is the most common in Omanis. Molecular diagnosis is necessary for accurate confirmation of the diagnosis of α-thal, determination of underlying genotypes, follow-up and counseling.

Prevalence and Genetic Analysis of α- and β-Thalassemia and Sickle Cell Anemia in Southwest Iran

This prospective study assessed the prevalence and genetic analysis of α- and β-thalassemia and sickle cell anemia (SCA) in Southwest Iran. Hematological indices were measured in 17,581 couples living in Khuzestan Province, Southwest Iran. Individuals with mean corpuscular volume <80, mean corpuscular hemoglobin <27, hemoglobin A2 ≥3/5 were considered as β-thalassemia traits. Prevalence of minor β-thalassemia, α-thalassemia, SCA, iron deficiency anemia, and silent thalassemia were respectively identified in 995 (5.6%), 1169 (6.65%), 1240 (7.05%), 911 (5.18%), and 1134 (6.45%) individuals using a multiplex amplification refractory mutation system, and direct DNA sequencing of globin genes. Three codons IVS-II-1 (G → A; 26%; n = 13), IVS-I-1 (G → T; 16%; n = 8), and IVS-I-110 (G → A; 14%; n = 7) were the most frequent mutants and IVS-II-1 was the most common β-thalassemia mutation. Also, based on a gap-polymerase chain reaction assay, genotype frequencies of α-globin mutations were -α^{3.7 kb} (50%; n = 25), Med/αα^thal (12%; n = 6), and -α4.2/αα (10%; n = 5), which were the most frequent deletion mutants (72% in total). The most common deletion (50%) was -α^{3.7 kb}. Our data suggest that the population of Southwest Iran is at high risk of α- and β-thalassemia caused by these deletion mutants and SCA. Our findings will be useful for developing an efficient control program and genetic counseling.

Alpha-globin gene mutation spectrum in patients with microcytic hypochromic anemia from Mazandaran Province, Iran

Background

It is estimated about 7% of the world population is carriers of hemoglobin diseases. Alpha‐thalassemia is one of the most common hereditary hemoglobin disorders in the world. This study investigated alpha‐globin mutations in potential carriers with hypochromic and microcytic anemia from Mazandaran, in northern Iran.

Methods

A total of 859 subjects were selected; genomic DNA was extracted and examined for the presence of mutations in the alpha‐globin genes.

Results

Mutation analysis of alpha‐globin genes revealed 27 different mutations. Seven variants were seen in 91.45% of all alpha‐1 and alpha‐2 mutations among patients in this study. The 3.7 kb deletion is the most frequent mutation with a frequency of 49.53%, followed by PolyA2 (15.19%), −4.2 deletion (8.76%), ‐‐MED (5.84%), IVSI‐5nt deletion (5.49%), Hb constant spring (3.62%), and Cd 19 (−G; 3.04%), respectively. There are also seven new variants which were reported for the first time either in alpha‐1 or alpha‐2 genes, including codon 9 (C > A; α2), deletion of codon 60 (AAG deletion; α2), duplication of codon 94‐100 plus 3 base pairs of intron 2 (IVSII + 3; α1), codon 99 (C > A; α2), codon 108 (A > G; α2), codon 128 (A > T; α2), and codon 129 (T > G; α2), respectively. The MLPA method also revealed three rare and novel deletions in alpha‐cluster region with about 30 kilobases long.

Conclusion

This study showed an efficient identification of α‐thalassemia can be achieved using standard hematological indices in our population. The details of these variations will help local genetic services for diagnostic and prenatal diagnosis services.

Molecular Basis of α-Thalassemia in Iran

Alpha-thalassemia (α-thal) is probably the most prevalent monogenic condition in the world. Deletions are the most common types of mutations in α-thal, followed by point mutations and small insertion/deletion. In the context of national screening program for prevention of thalassemia and hemoglobinopathies in Iran, α-thal carriers have come to more attention. Therefore, the frequency and distribution of α-globin mutations in various regions of the country have been studied in recent years. A comprehensive search was performed in PubMed, Scopus, and national databases for finding reports on mutation detection in α-thal carriers and HbH disease with Iranian origin. The mutation data of 10849 α-thal carriers showed that -α^3.7 and α^-5NT were the most common deletional and nondeletional mutations, respectively. In HbH disease cases, the -α^3.7/--^MED was the most prevalent genotype. Overall, 42 different mutations have been identified in α-globin cluster reflecting the high heterogeneity of the mutations in Iranian populations.

A Comprehensive Molecular Investigation of α-Thalassemia in an Iranian Cohort from Different Provinces of North Iran

α-Thalassemia (α-thal) is the most common monogenic disease that is caused by the absence or reduced expression of α-globin genes. The aim of this study was to investigate common α-globin mutations and their associated haplotypes in four northern provinces of Iran (Gilan, Mazandaran, Golestan, Khorasan). One thousand, one hundred and ninety-one persons were tested for α-thal mutations by gap-polymerase chain reaction (PCR), reverse dot-blot hybridization, restriction fragment length polymorphism (RFLP) analysis and sequencing. Of the nine different mutations found, the most frequent were -α^3.7 (rightward deletion) (45.6%), polyadenylation site (α^p°^lyA2α) (α2) (AATAAA>AATGAA; HBA2: c.*92 A>G) (15.27%), - -^MED (Mediterranean deletion) (6.86%), -α^4.2 (leftward deletion), (6.17%), α^CSα [Hb Constant Spring (Hb CS) (HBA2: c.427 T>C)] (4.62%), -α^-5 nt (HBA2: c.95+2_95+6delTGAGG) (3.70%). All chromosomes bearing an α-globin point mutation [α^p°^lyA2α, -α^-5 ntα, α^CSα, α^p°^lyA1α (AATAAA> AATAAG; HBA2: c.*94 A>G)] showed only one haplotype that was present in most normal chromosomes, while the -α^3.7 deletion was associated with three distinct haplotypes. Our results indicate that α-thal mutations are heterogeneous and -α^3.7 and α^p°^lyA2α are the most prevalent mutations in this region. The presence of -α^3.7 with three different haplotypes suggests an older history for this mutation. The high prevalence of α^p°^lyA2α in Mazandaran Province, Iran compared to other parts of the country and the world, suggests a founder effect. Altogether, we here provide further data confirming the heterogeneity of the northern population of Iran. These data may contribute to the establishment of a national mutation database, more accurate genetic counseling and prenatal diagnosis (PND).

Novel Mutation of the Translation Initiation Codon of the α1-Globin Gene (ATG>AAG or HBA1:c.2T>A)

We report two Italian-Canadian families with α⁺-thalassemia (α⁺-thal) trait caused by a novel mutation of the translation initiation codon of the α1-globin gene (ATG>AAG or HBA1:c.2T>A). This is the tenth reported α-thal mutation involving the translation initiation codon or the conserved Kozak consensus sequences of the HBA2 or HBA1 genes.

HB Puerta del Sol [HBA1:c.148A>C], HB Valdecilla [HBA2:c.3G>T], HB Gran Vía [HBA2:c.98T>G], HB Macarena [HBA2:c.358C>T] and HB El Retiro [HBA2:c.364_366dupGTG]: description of five new hemoglobinopathies

BACKGROUND

Structural hemoglobinopathies do not usually have a clinical impact, but they can interfere with the analytical determination of some parameters, such as the glycated hemoglobin in diabetic patients. Thalassemias represent a serious health problem in areas where their incidence is high. The defects in the post-translational modifications produce hyper-unstable hemoglobin that is not detected by most of electrophoretic or chromatographic methods that are available so far.

METHODS

We studied seven patients who belong to six unrelated families. The first two families were studied because they had peak abnormal hemoglobin (Hb) during routine analytical assays. The other four families were studied because they had microcytosis and hypochromia with normal HbA2 and HbF without iron deficiency. HbA2 and F quantification and abnormal Hb separation were performed by chromatographic and electrophoretic methods. The molecular characterization was performed using specific sequencing.

RESULTS

The Hb Puerta del Sol presents electrophoretic mobility and elution in HPLC that is different from HbA and similar to HbS. The electrophoretic and chromatographic profiles of the four other variants are normal and do not show any anomalies, and their identification was only possible with sequencing.

CONCLUSIONS

Some variants, such as Hb Valdecilla, Hb Gran Vía, Hb Macarena and Hb El Retiro, have significant clinical impact when they are associated with other forms of α-thalassemia, which could lead to more serious forms of this group of pathologies as for HbH disease. Therefore, it is important to maintain an adequate program for screening these diseases in countries where the prevalence is high to prevent the occurrence of severe forms.

The Spectrum of α-Thalassemia Mutations in Kermanshah Province, West Iran

Thalassemia is a hereditary blood disorder that results from genetic defects causing deficient synthesis of hemoglobin (Hb) polypeptide chains. Although thalassemia mostly affects developing countries, there is limited knowledge of its accurate frequency and distribution in these regions. Knowing the prevalence of thalassemia and the frequency of responsible mutations is therefore an important step in the prevention and control program as well as treatment strategies. α-Thalassemia (α-thal) is prevalent in Middle East Asian populations, including Iran. In this study, 678 unrelated α-thal carriers, attending the Kermanshah Medical Genetics Laboratory, Kermanshah, Iran, were investigated for α-globin gene mutations by multiplex polymerase chain reaction (PCR) and direct sequencing. The most common mutation among our patients was -α(3.7) (rightward) (60.9%) deletion, which is also known to occur in high frequencies in other parts of Iran, in Southeast Asia and Mediterranean countries. Other prevalent α-thal mutations were α(-5 nt) (10.6%), α(polyA4) (9.9%), α(polyA6) (3.7%), - -(MED) (3.2%), -α(4.2) (leftward) (3.1%) deletion and codon 59 (Hb Adana; HBA1: c.179 G > A) (2.5%). These comprehensive new data are useful for establishing a screening strategy for the effective control of α-thal in Kermanshah Province.

Alpha-thalassemia mutations in adana province, southern Turkey: genotype-phenotype correlation

To look over the distribution of the mutations in a large series from Adana province, Southern Turkey, and determine the genotype-phenotype correlation of the frequent mutations. Among the 2500 individuals with mild or moderate anemia, microcytosis, and normal iron levels that were referred to our Genetic Diagnosis Center, a population consisting of 539 individuals were included in the study and tested for alpha-thalassemia mutations by using reverse dot blot hybridization technique. Twelve different mutations were detected in 539 patients. Among the 12 different mutations found, the most frequent mutations were the -α(3.7) (63.3 %), --(MED) (11.7 %), --(20.5) (10.7 %), α2(IVS1(-5nt)) (3.9 %), and α2(polyA-2) (3.5 %). The most frequent genotypes were -α(3.7)/αα (35.8 %), -α(3.7)/-α(3.7)(18.9 %), -(20.5)/αα (11.5 %), and --(MED)/αα (10.4 %), respectively. There were statistically significant differences in hematological findings between -α(3.7)/-α(3.7) and --(MED)/αα, even though both have two mutated genes in the genotype. Our results show that alpha-thalassemia mutations are highly heterogeneous as well as deletional and -α(3.7) single gene deletion is particularly prevalent at Adana province in agreement to other studies from Turkey.

Genetic epidemiology, hematological and clinical features of hemoglobinopathies in Iran

There is large variation in the molecular genetics and clinical features of hemoglobinopathies in Iran. Studying structural variants of hemoglobin demonstrated that the β-chain variants of hemoglobin S and D-Punjab are more prevalent in the Fars (southwestern Iran) and Kermanshah (western Iran) provinces, respectively. Also, α-chain variants of Hb Q-Iran and Hb Setif are prevalent in western Iran. The molecular basis and clinical severity of thalassemias are extremely heterogenous among Iranians due to the presence of multiethnic groups in the country. β-Thalassemia is more prevalent in northern and southern Iran. Among 52 different β-thalassemia mutations that have been identified among Iranian populations, IVSII-1 G:A is the most frequent mutation in most parts of the country. The presence of IVS I-5 G:C mutation with high frequency in southeastern Iran might reflect gene flow from neighboring countries. A wide spectrum of α-thalassemia alleles has been detected among Iranians with -α(3.7 kb) as the most prevalent α-thalassemia mutation. The prevention program of thalassemia birth in Iran has reduced the birth rate of homozygous β-thalassemia since the implementation of the program in 1997. In this review genetic epidemiology, clinical and hematological aspects of hemoglobinopathies, and the prevention programs of β-thalassemia in Iran will be discussed.

A report of 8 cases with hemoglobin H disease in an Iranian family

alpha-Thalassemia is a common genetic disorder in Iran. However, no comprehensive data on epidemiology of severe forms of alpha-thalassemia, including hemoglobin H (HbH) or hydrops fetalis, is available in this population. This is a first case report of an Iranian family with large number of HbH individuals. The proband is a 48-year-old woman, referred to our center with anemia and no history of previous blood transfusions. Similar clinical phenotype has been observed in all of her 5 siblings, 2 of her 4 children, and her granddaughter, whose parents are first cousins. A reverse hybridization assay covering 21 alpha globin mutations was performed to determine the genotype in 11 members of this family and a fetus. HbH genotype was identified in 9 individuals, representing 3 generations, including a fetus. The high prevalence of alpha-thalassemia carriers together with the high rate of consanguineous marriages could lead to a large number of individuals with HbH or even hydrops fetalis in Iranian families. Therefore, to avoid the risk of having affected offspring, carrier detection, genetic counseling, and prenatal diagnosis would be of vital importance for individuals with low red blood cell (RBC) indices, normal iron status, and normal HbA(2) level, who are suspected to be alpha-thalassemia carriers.