Genetic Profiling and frequencies of Modifiers in Transfusion-Dependent Thalassemia

Thalassemia is a genetic blood disorder primarily influenced by β-globin gene mutations and various genetic modifiers. In Pakistan, especially among transfusion-dependent thalassemia (TDT) patients, data on these modifying factors remain limited, hindering accurate diagnosis and tailored management. This study aimed to reassess the diagnostic classification and determine the frequency of genetic determinants specifically alpha-thalassemia deletions and key polymorphisms (BCL11A and Xmn1-HBG2) associated with milder clinical phenotypes in multi-transfused thalassemia patients from the local population.

This descriptive cross-sectional study was conducted over a six-month period, from January to June 2019 and included 54 TDT patients aged up to 15 years from the Fatimid Foundation, Peshawar. Genetic analyses were performed for polymorphisms at Xmn-1-HBG2 and BCL11A, as well as for two alpha (α) and thirteen common beta (β) gene alterations. Utilizing the PureLinkTM Genomic DNA Kit, DNA was retrieved. The ARMS technique was used to identify β-thalassemia mutations, whereas Gap-PCR was used to identify α-thalassemia deletions. For Xmn-1 genotyping, we used RFLP-PCR, while ARMS-PCR was used to assess BCL11A polymorphisms.

All patients had either homozygous or compound heterozygous mutations in the β-globin gene. Of them, 38 patients had BCL11A polymorphisms, two had Xmn-1-HBG2 polymorphisms and 11 patients had a co-existing heterozygous α (3.7 kb) deletion. Homozygous Fr 8-9 was the variant with the most common mutation, occurring in 19 (35.2%) cases. Isolated β-globin gene mutations were found in just 13 cases. Together with the underlying β-globin mutation, 85.2% patients had an additional ameliorating genetic component (a BCL11A polymorphism, Xmn-1-HBG2 polymorphism, or α-globin gene mutation).

Transfusion-dependent β-thalassemia patients in Peshawar Region often have co-existing genetic modifiers, resulting in a milder phenotype. Screening for these modifiers is recommended for specialized treatment in these children.