Genotype analysis of 55,281 cases of thalassemia in northern Guangxi

To understand the genotype and distribution of thalassemia in northern Guangxi.

The study subjects were 55,281 individuals who came to the Affiliated Hospital of Guilin Medical University for genetic diagnosis of thalassemia from January 2012 to August 2023. All of their household registration was in the precincts of Guibei District and its affiliated counties. Red blood cell parameters and hemoglobin analysis were used for thalassemia screening. Gap-PCR, PCR-reverse dot blot hybridization (PCR-RDB), and multicolor melting curve analysis (MMCA) were used to identify common thalassemia genes. Multiplex ligation-dependent probe amplification (MLPA), Sanger sequencing, and third-generation single-molecule real-time (SMRT) sequencing were employed to identify rare thalassemia genes.

Among the 55,281 samples, 16,442 (29.74%) were diagnosed with thalassemia. The detection rates of α, β, and α combined β-thalassemia were 18.57%, 9.99% and 1.18%, respectively. Among ethnical groups, allele mutation frequency of thalassemia was the highest in Zhuang (44.97%), followed by Yao (40.11%), Dong (31.33%), Han (29.85%), Miao (24.31%), and Hui (20.6%). A total of 11,659 alleles (21.09%) of 8 types of α-thalassemia were identified in 55,281 samples, primarily --^SEA (53.9%), followed by -α^3.7 (21.3%), including rare alleles: --^THAI (0.45%) and HKαα (0.38%). A total of 6367 (11.52%) and 14 types of β-thalassemia alleles were identified, mainly CD41-42 (50.12%), followed by CD17 (22.22%), including rare alleles: β^CD37 (0.16%) and Gγ⁺ (Aγδβ)⁰/β^N (0.05%). A total of 31 genotypes were detected in 10,264 cases of α-thalassemia, and the main types were --^SEA/αα (53.23%), -α^3.7/αα (19.15%), and -α^4.2/αα (7.21%). A total of 34 genotypes were detected in 5525 cases of β-thalassemia, and the main types were β^CD41-42/β^N (50.53%), β^CD17/β^N (21.77%), and β^IVS-II-654/β^N (12.16%). A total of 78 gene types were detected in 653 cases of α- and β-thalassemia, and the main types were --^SEA/αα, β^CD41-42/β^N (18.68%) and -α^3.7/αα, β^CD41-42/β^N (13.02%). There were 580 cases (5.65%) of HbH disease (α⁰/α⁺), and 4 cases of Hemoglobin Bart's Hydrops Foetus syndrome (--^SEA/--^SEA). In addition, there were 92 cases (1.67%) of intermedia or severe types of β-thalassemia (β⁰/β⁰, β⁰/β⁺, β⁺/β⁺), including 23 cases of combined α-thalassemia. Among the samples screened negative for thalassemia, 3.7% of them were found to carry thalassemia genes, and 91.35% of the genotypes were α^WSα/αα, -α^3.7/αα, and -α^4.2/αα. In addition, 40.26% of α^WSα/αα, 22.89% of -α^3.7/αα, and 18.51% of -α^4.2/αα had no hematological phenotype.

The population in northern Guangxi exhibited rich ethnic diversity, with high allelic carrying rates among the Zhuang, Yao and Dong ethnic groups. Thalassemia gene mutations are diverse, encompassing a variety of gene types, with α thalassemia predominating, notably the --^SEA/αα gene type. The prevalence of intermedia or severe types of thalassemia is not low, but there are still some carriers of thalassemia in people who are initially tested negative.