Genotypic Characterization of Hemoglobinopathies in Azerbaijan: A Review of 10 Years at a Referral Center

Hemoglobinopathies constitute a major cause of hereditary anemia and remain a significant public health challenge in Azerbaijan. The purpose of this study was to delineate the variant spectrum and genotype distribution in a large national cohort and to evaluate the contribution of next-generation sequencing (NGS) to molecular diagnosis. During the study period, 1,000 unrelated individuals with suspected hemoglobinopathies underwent hematological and molecular genetic evaluation at a national referral center in Azerbaijan. Overall, 777 of 1,000 (77.7%) individuals were genetically positive. Of these, β-thalassemia was most frequent (59.9%, 466/777), followed by α-thalassemia (22.0%, 171/777) and co-inheritance of α/β-thalassemia (9.52%, 74/777). In addition, HbS-related genotypes were detected in 6.2% (48/777) and other rare hemoglobin variants in 1.3% (10/777). In α-thalassemia, the most common genotypes were αα/-α³·⁷ (22.81%), -α³·⁷/-^20.5 (17.54%), and αα//^-20.5 (16.37%), while the predominant alleles were - α³·⁷ (n = 76) and -20.5 (n = 72). In β-thalassemia, the leading alleles were c.25_26delAA (codon 8 - AA; 19.74%), c.315 + 1G > A (IVS-II-1; 8.91%), and c.93-21G > A (IVS-I-110; 5.58%), which together accounted for ∼35% of mutant alleles. The large deletional variants, including Sicilian and Turkish (δβ)⁰ deletion, and Hb-Lepore, were also identified, highlighting the importance of deletion-focused assays. Notably, a novel HBA2 start-codon variant (c.3G > A; p.Met1Ile, Hb Baku) and a previously unreported splice variant in HBB (c.315 + 3_+4insT) expanded the mutational landscape. The broad spectrum of small sequence variants and large genomic alterations, including rare and novel findings, underscores the limitations of targeted assays and supports the integration of comprehensive NGS-based diagnostics into national screening and prevention programs.