The Molecular Basis of Beta-Thalassemia Intermedia in Egyptian Children and its Association with the Clinical Phenotype

Abstract Background β-thalassemia syndromes involve a collection of extremely diverse phenotypes. The term β-thalassemia intermedia (β-TI) was suggested to describe patients who had clinical manifestations that are too severe to be termed minor thalassemia yet too mild to be termed major thalassemia. However, there remains substantial overlap between the three conditions. Aim of the Work To evaluate the variable clinical phenotypes among pediatric patients with βTI and to study the phenotype / genotype correlation with the encountered β-chain mutations. Patients and Methods A cross-sectional study was conducted on 37 Egyptian children and adolescents with TI following up regularly in the Pediatric Hematology clinic – Ain Shams University. Detailed Clinical evaluation and laboratory investigations were done. Reverse hybridization PCR based assay covering beta globin Mediterranean mutations onto specific biotinylated primers, was done. Results IVS 1.6 (T>C) was the most frequent mutation detected in 20 patients and 31 alleles (47.7%), followed by IVS 1.110 (G>A) detected in 7 patients and 8 alleles (12.31%), followed by IVS 1.1 (G>A) and CD27 knossos (G>T), each was detected in 6 patients and 6 alleles (9.23%). β+β+ was the most frequent genotype (54%), followed by β+β/β°β (21.6%) and β°β+ (13.5%). 60% of β°β+ patients had TDT(Transfusion dependent thalassemia), while 87.5% of β + β/β°β patients and 55% of β + β+ patients had NTDT ((Non transfusion dependent thalassemia). Conclusion Inheritance of mild β+ thalassemia mutations among Egyptian children; as IVS 1.6 (T>C) and IVS 1.110 (G>A) is the most frequent contributor to TI phenotype in either homozygous or compound heterozygous states. Patients with the same underlying genotype presented variable phenotypes with different degrees of severity.