PREVALENCE AND MUTATIONS OF β-THALASSEMIA TRAIT
AND ABNORMAL HEMOGLOBINS IN PREMARITAL
SCREENING IN ÇANAKKALE PROVINCE, TURKEY
Uludağ A, Uysal A, Uludağ A, Ertekin YH, Tekin M, Kütük B, Sılan F, Özdemir Ö
*Corresponding Author: Associate Professor Ahmet Uysal, Department of Obstetrics and Gynecology,
Çanakkale Onsekiz Mart University, Terzioglu Yerleskesi 17100, Çanakkale, Turkey. Tel: +90-533-263-
5540. Fax: +90-028-626-3597. E-mail: drahmetuysal@hotmail.com
page: 29
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DISCUSSION
β-Thalassemia is a well-known genetic disorder
of the globin gene, with a worldwide distribution. The
Ministry of Health and the Turkish National Hemoglobinopathies
Council (MH and TNHC) reported a 4.3%
prevalence of β-thal trait in a population of 377,399
healthy subjects from 16 cities in Turkey [6]. However,
no study has reported the prevalence of β-thal trait and
abnormal Hbs for the province of Çanakkale until now.
Çanakkale is located in the far west of Turkey between
the Marmara and Aegean regions. Different to
other areas of Turkey, the majority of the population
is comprised of immigrants from Balkan countries
and Romania. The sociocultural level of the city is
above Turkey average.
Our study is the first to report these data, save
for our preliminary premarital screening report of
1.45% limited to the city of Çanakkale alone. This rate
was 0.06% for Hb S (HBB: c.20A>T) carriers. This
prevalence of β-thal carriers in the province is not high
compared to the prevalence in Turkey as a whole. In
İzmir (in the Aegean region of Turkey), the neighboring
provinces of Çanakkale, the prevalence of β-thal
and Hb S were 4.96 and 0.13%, respectively [3].
In Turkey, 36 different β-thal mutations have been
described to date. The most commonly identified mutations
are, in order, HBB: c.93-21G>A, HBB: c.92+6T>C
[IVS-I-6 (T>C)] and HBB: c.25_26delAA [codon 8
(‒AA)] [2]. In the Mediterranean region, 19 different
mutations have been reported and the most frequently
observed are HBB: c.93-21G>A, HBB: c.92+6T>C and
HBB: c.-80T>A [‒30 (T>A)] mutations. The same study
reported the Hb S incidence as 10.3% [7].
This wide molecular variety, the molecular genetic
description of the disease, significantly hampers
strategies and programs to prevent the disease. In
our region, according to the β-globin genetic analysis
we conducted, there were 14 different mutations
identified in carriers of β-thal. The most frequently
observed mutation for β-thal in Turkey with a rate
of about 40.0% is reported as HBB: c.93-21G>A [2].
In our study, this mutation has the highest frequency
of 26.08%, lower than the average for Turkey and
different to a range of regions in Turkey [2,7-9]. The
frequency of HBB: c.93-21G>A in β-thal mutations exceeds 50.0% in Central Anatolia, but falls to 25.0%
in East and Southeast Anatolia [2,10,11]. Keser et al.
[8] calculated the frequency of HBB: c.93-21G>A as
35.6% in the Antalya region in their 2004 study. The
same mutation was reported as 49.02% in the Central
Anatolia region by Beksaç et al. [9,11].
Interestingly, although there are so many immigrants
in Çanakkale from the Balkans, who came
during the Balkan War (1912), the mutation profile is
different from Balkan countries, especially Romania
[12]. Selected marriages because of cultural differences
in those days may cause this difference.
As seen in our study, β-thal is an important health
problem in Turkey. As there is no certain treatment
of β-thal, it is very important to determine the mutations
and the carriers for preventing the disease. For
correct genetic counseling it is necessary to know the
exact mutations within the families. The couple both
found to be β-thal carriers in our study did not have
genetic counseling so they had lost their first child
because of β-TM. Prenatal diagnosis by amniocentesis
of the fetus for their second pregnancy was found
to be homozygous for a normal β-globin gene. This
dramatic family history emphasizes the importance
of prenatal screening, especially for carriers. The
wide heterogeneity of β-thal at a molecular level is
an important barrier to diagnosis and prevention of
the disease. This is the first report on the frequency and mutation
profiles of β-thal for Çanakkale. The incidence
of β-thal carriers in Çanakkale is below the average
of Turkey. A high level of sociocultural population
and low rates of consanguineous marriages could
cause this. The most frequently observed mutation
profile and rate of β-thal in our region is different to
the mutation profiles and rates observed in different
regions of Turkey. To prevent an increase in β-thal
incidence and ensure families become parents of
healthy children, it is necessary to increase consanguinity
marriage education, genetic counseling before
pregnancy and prenatal genetic screening programs.
Declaration of Interest. The authors report no
conflicts of interest. The authors alone are responsible
for the content and writing of this article.
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