IMPACT OF COINHERITANCE OF A-THALASSEMIA ON PHENOTYPE IN IRAQI KURDS WITH HOMOZYGOUS AND COMPOUND HETEROZYGOUS SEVERE Β -THALASSEMIA

Abstract

Background: Patients with homozygous or compound heterozygous β0 thalassemia may present either with thalassemia major or intermedia. This phenotypic variability is the consequence of several genetic modifiers in different populations. We aimed to assess the frequency and the impact of coinheritance of α-thalassemia on phenotype in Iraqi Kurds. Methods: A total of 125 patients characterized as homozygous or compound heterozygous β0 thalassemia were recruited in thalassemia center Duhok. They were classified based on age of starting and the frequency of transfusion (thalassemia major or intermedia). All patients had their DNA extracted and Gap-PCR performed to identify 3 deletions namely: ‒α 3.7, ‒α 4.2, and ‒ ‒MED. Results: The patients had a median age of 12 years (Range 2.0-35), with 63 males and 62 females. 96 patient with thalassemia major and 29 with intermedia. The most frequent β-mutations were IVS-2.1 (G>A), Codon 44 (-C), codon 5 (-CT) and codon 8 (-AA). Gap PCR identified α-thalassemia in 9 patients (7.2%), including ‒α 3.7 /αα in 8 cases and ‒α 4.2/αα in one patient, while none had a double α-gene deletions. The frequency of α-thalassemia was higher in thalassemia intermedia at 13.8% compared to 5.2% in major. This difference was statistically insignificant (P=0.228). Conclusions: The patients not appear to be a significant with homozygous or compound heterozygous β0 thalassemia. This may be attributed to low background frequency of α-thalassemia, it being mainly due to a single α-gene deletion. Further studies including more patients with extended β-genotypes and other genetic modifiers may be worthwhile.