Study of the Effect of HFE Gene Mutations on Iron Overload in Egyptian Thalassemia Patients

Introduction: β-thalassemia is a common genetic disorder affecting the β-globin gene, characterized by ineffective erythropoiesis and iron overload. It is the most common hereditary hemolytic anemia in Egypt(85.1%)with a carrier rate of 5.3to 9% and annual birth of 1000/1.5million live births born with the disease. Mutations in the HFE gene have been shown to be responsible for hereditary hemochromatosis, an autosomal recessive disease of iron overloading. The effect of these mutations on iron load in β- thalassemia patients and carriers remains controversial. Interaction between β- thalassemia and hemochromatosis may increase the likelihood of developing iron overload in thalassemic patients and thus may require early iron chelation.

Objectives:In this cross-sectional case-control study, we aimed to determine the prevalence of HFE gene mutations (C282Y and H63D) in β- thalassemia patients and carriers and to investigate the effect of these mutations on their serum ferritin levels.

Patients and Methods: A total of100 β-thalassemia subjects; 75 β- thalassemia patients (homozygous or compound heterozygous) and 25 carriers were screened for HFE gene mutations (H63D and C282Y) by polymerase chain reaction-restriction fragment length polymorphism method (PCR-RFLP). Serum ferritin was measured for all subjects by enzyme-linked immunosorbant assay (ELISA) and β-globin gene mutations were determined by reverse hybridization technique. All β- thalassemia patients (45 males and 30 females with mean age 3.2 + 2.7 years) were diagnosed and followed at at our Pediatric Hematology Clinic. Their baseline serum ferritin at diagnosis was evaluated in relation to the HFE mutations. Twenty-five heterozygotes for β- thalassemia attending for genetic screening or parents or sibs of our patients were enrolled as carriers. All subjects and/or guardians gave informed consent before enrollment.

Results: Twenty- eight of 75 β- thalassemia patients (37.3%) were heterozygotes for the H63D mutation (H/D), 8 (10.7%) were D/D homozygotes and 39 (52%) were negative for the mutation( H/H homozygotes). Among carriers, 4 (16%) were D/D homozygotes and 21 (84%) were H/H homozygotes(Fig1) . The C282Y mutant allele was not detected in any of patients or carriers. The median serum ferritin level was significantly higher in β- thalassemia patients compared to carriers (386 vs. 216 ng/ml; p=0.03). Serum ferritin levels were compared according to H63D genotypes in β- thalassemia patients and carriers (Table 1). There were significantly high levels of serum ferritin in β-thalassemia patients who were heterozygotes or homozygotes for the H63D mutation compared to those without the mutation (p=0.000).B-Thalassemia carriers homozygotes for the H63D mutation showed significantly higher serum ferritin levels compared to those without the mutation (P<0.001). The most prevalent underlying genetic mutation of β globin gene in our β-thalassemia patients was IVS 1.110 mutation followed by IVS 1.6.

This study showed no correlation between these mutations and the H63D genotype.

Conclusion:Homozygosity for the H63D mutation tend to be associated with higher ferritin levels in beta-thalassemia patients and carriers compared to the H/H genotype, suggesting that the H63D mutation may have a modulating effect on iron load. Screening of H63D mutation in β-thalassemia patients may predict patients with more tendency to develop early iron overload. Proper timely management of these patients prevents the hazard of iron overload.

Figure (1):

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H63D polymorphism of the HFE gene in β-thalassemia patients and carriers

Figure (1):

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H63D polymorphism of the HFE gene in β-thalassemia patients and carriers

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p-values: H/H vs. H/D; H/D vs. D/D;H/H vs. D/D < 0.001*