The Carrier Frequency of α-Globin Gene Triplication in an Iranian Population with Normal or Borderline Hematological Parameters

The -α(3.7) rightward deletion is the most frequent α-globin mutation worldwide, while frequencies of the ααα(anti 3.7) triplication are only sporadically known. Carriers of the ααα(anti 3.7) triplication show no clinical symptoms or significant hematological changes, but co-inheritance with β-thalassemia (β-thal) has been reported to worsen the clinical and hematological features of the patient as well as the trait. We have screened the α-globin gene rearrangements of 280 individuals with normal hematological indices and 117 persons with borderline hematological parameters. We used multiplex polymerase chain reaction (m-PCR) and multiplex ligation-dependent probe amplification (MLPA) technology to detect triplications and quadruplications. Only the ααα(anti 3.7) triplication was observed. The carrier frequency in the first group was 2.14% and in the second group 1.7%. No phenotype aggravation was noticed in two carriers of β-thal and the ααα(anti 3.7) triplication, while a mild β-thalassemia intermedia (β-TI) was observed in a β-thal carrier with six α-globin genes. Due to the high consanguinity in the country, homozygosity for the ααα(anti 3.7) triplication and for other rearrangements can be expected. Therefore, an accurate determination of the frequencies and a routine control for these mutations is essential for a correct genotype-phenotype prediction during genetic counseling for β-thal.