Evaluation of α-Globin Gene Mutations Among Different Ethnic Groups 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.

Fertility and pregnancy in Iranian thalassemia patients: An update on transfusion complications

BACKGROUND

Despite the significant advances in thalassemia pathobiology and efficacy of chelation regimens, complications of transfusion therapy have attenuated the reproductive health of thalassemia patients. Depending on clinical profiles, we aimed to assess the fertility status and stresses among thalassemia patients who desired to have children.

MATERIAL AND METHODS

A total of 213 couples in reproductive ages were enrolled in this study in Tehran. Patients' demographic, clinical, fertility and spouse's health status were documented. We evaluated the pituitary-gonadal axis, serum ferritin, liver enzymes, and alloimmunization before planning a pregnancy and reported them as a function of spontaneous conception and transfusion dependency.

RESULTS

Data showed that 131 patients (62%) had 228 spontaneous pregnancies leading to 198 (86.6%) successful pregnancies. A significant difference was observed in spontaneous pregnancy with respect to fertility complications and transfusion dependency. In addition, the clinical conditions of spouses in patients with any spontaneous pregnancy were more thalassemia carriers (P < .05). Moreover, serum ferritin levels had a significant negative correlation with the levels of Testosterone, Estradiol, luteinizing hormone, and follicle-stimulating hormone. Furthermore, a significant positive correlation was reported with the level of liver enzymes. Finally, alanine transaminase and aspartate transaminase had a significant negative correlation with pituitary hormones.

CONCLUSION

We suggest that organised instruction in addition to good iron chelation, especially during the puberty period, would reduce the oxidative damage and related complications in thalassemia patients. Moreover, infertility seems to be attributed to iron deposition in various endocrine organs, pituitary, reproductive system and the liver, contributing to hormonal metabolism.

Detection of a Large Novel α-Thalassemia Deletion in an Autochthonous Belgian Family

α-Thalassemia (α-thal) is a common hemoglobinopathy mainly caused by deletion of one or both α-globin genes. We describe an autochthonous Belgian family diagnosed with α-thal trait. Molecular analysis revealed a novel large deletion of at least 170 kb between 226.68 kb (0.2 Mb) and 402.68 kb (0.4 Mb) from the telomere of 16p, leaving the subtelomeric region intact. The deletion includes both α-globin genes (HBA1 and HBA2) but also flanking genes possibly related to non hematological effects: HBQ1, LUC7L, ITFG3, RGS11, ARHGDIG, PDIA2 and AXIN1. These genes are not contained in the region (0.9 and 1.7 Mb from the telomere of 16p) associated with α-thal intellectual disability (ATR-16) syndrome. However, further research is necessary to exclude other potential effects than α-thal in patients with a large deletion at 0.2-0.4 Mb from the telomere of 16p. Genetic counseling is important for carriers of this deletion as homozygosity for the α-globin (- -/) haplotype may lead to Hb Bart's (γ4) hydrops fetalis syndrome.

First Report of Association Between Rare α-Thalassemia Mutation (HBA1: c.298A>T) and Hb Fontainebleau (HBA2: c.64G>C)

α-Thalassemia is one of the most common monogenic diseases worldwide. The combination of alpha-chain variants with thalassemia mutations may lead to clinical and hematological characteristics, which is of importance for genetic counseling. The present study describes for the first time a rare α1-globin nonsense mutation, codon 99 (HBA1: c.298A>T) associated with a α₂-chain variant Hb Fontainebleau (HBA2: c.64G>C) in a family from northern Iran. The case is a 23-year-old man with hypochromic microcytic anemia that requested for prenatal diagnosis. The combination of α1-globin mutation and Hb Fontainebleau can cause clinical and hematologic features of thalassemia. This combination also highlights the important heterogeneity of alpha thalassemia in this part of the world.

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.