Genotype-phenotype correlation and mutation spectrum of HBB gene in the Hatay province of Turkey

Purpose: Thalassemia carriage and hemoglobinopathies are quite common disorders in Turkey, especially in the cukurova region, including Hatay province. Due to the high case population and genetic diversity in our region, this study aimed to investigate the genotype-phenotype correlation in the HBB gene. Materials and Methods: The data of patients who applied to Hatay Mustafa Kemal University Medical Genetics or Hematology Clinic between January 2010 and November 2022 were evaluated retrospectively. Results: A total of 40 (100%) cases, comprising 25 (62.5%) homozygous and 15 (37.5%) compound heterozygous genotypes, were included in the study based on the mutation profiles in the HBB gene. In the analysis of the cases, it was seen that there were 17 different variants and 22 distinct genotypes. The three most common variants identified in this study were IVS-I-6 (T>C), IVS-I-1 (G>A), and IVS-II-848 (C>A). Of the cases with homozygous genotypes, 13 (52%) had the IVSI-6 (T>C) variant. The most frequent genotypes observed in cases with compound heterozygous genotype were IVSI-6 (T>C)/IVS-I-110 (G>A), IVS-I-6 (T>C)/Hb Knossos, and IVS-I-110 (G>A)/-101 C>T, each in 2 (13%) cases. Conclusion: This study provides information on the phenotypic characteristics of very rare genotypes. We think that this information will be very beneficial, especially for clinicians interested in prenatal diagnosis, preimplantation genetic diagnosis, and postnatal genetic counseling.