Abstract
β
-thalassemia is a group of heterogeneous recessive disorders common in many parts of the world. Al-Qatif and Al-Hassa oases in the Eastern Province of Saudi Arabia are regions known for high frequency of these disorders. Using two molecular methods, based on multiplexing-amplification refractory system and reverse hybridization principles, the spectrum of
β
-thalassemia in the region was studied. Sixty-nine subjects with known
β
-thalassemia disease and volunteers with high hemoglobin
A
2
(
HbA
2
)
and low mean corpuscular volume (MCV) were included in this study. Ten mutations were detected in 91% of the subjects under study. Six of these mutations had previously been observed while the other four mutations are reported here for the first time. In addition, four of the mutations accounted for
76.8
% of the subjects studied. IVSII-1 (G
>
A), IVSI-5 (G
>
A), and codon 39 (C
>
T) mutations were found to be the most frequent. However, the frequencies of different mutations reported here are slightly different from those reported earlier. A number of these mutations were also found in the neighboring countries, which can be explained in terms of gene flow.