Abstract
Introduction: Although B-thalassaemia is one of the most common genetic disorders in Iraq with an estimated carrier prevalence of 4.6%, to date molecular data on the patterns of causative disease mutations have been very limited.
Objectives: To determine the spectrum of mutations present in patients clinicalty diagnosed with B-thalassaemia attending the lbnalbaldy Thalassemia Centre In Baghdad.
Methods: Blood samples were obtained from a group of 100 unrelated male and female patients aged 7-12 years. DNA was obtained by phenol/chloroform extraction and the l3-gtobin gene was amplified in three overlapping fragments using the polymerase chain reaction. followed by direct DNA sequencing in an ABI 3730x1 96-capillary automated DNA sequencers with Big Dye terminator chemistry
Results: Four mutations accounted for more than 80% of the thalassaemic chromosomes analysed: betas IVSII 1 G>A (HBB:c.315+1G>A), IVSI-1 10 (G->A) beta (HBB:c.93-21G>A), beta IVSI 6 bC (HBB:c.92+6T>C), and the frameshift mutation at CdS6/37 (—T) betaC (HBB:c.ll2detT). Each of these mutations is common in the Mediterranean region and among Arab populations.
Conclusion: These initial results indicate that analysis of DNA samples for the four common 13- globin gene mutations would provide good coverage for 13-thalassaemia carrier screening In the study population. However, given the ethnic sub-divisions in the Iraqi population, the strong tradition of marriage within clan and tribal boundaries, and an overall consanguineous marriage rate of 40-50%, it seems probable that more detailed community-specific studies will be required in the future.