β-Thalassemia, HB S-β-Thalassemia and Sickle Cell Anemia Among Tunisians

Abstract

We analyzed the mutations present in 19 patients with β-thal-assemia major, in 11 patients with Hb S-β-thalassemia, and the B^s haplotypes of 34 patients with sickle cell anemia. The study included 84 relatives. Dot-blot analysis of amplified DNA with various specific oligonucleotide probes identified 11 different known β-thalassemia mutations and frameshifts; a new frameshift at codons 25/26 (+T) was detected through sequencing of amplified DNA. The common β-thalassemia mutations at codon 39 (C→T) and at IVS-I-110 (G→A) were also most prevalent among the Tunisian patients, while the milder T→C mutation at IVS-I-6 was not found. All mutations cause a Bd`-thalassemia or a severe B⁺-thalassemia [T→A at -30; IVS-I-5 (G→A); IVS-I-110 (G→A)] which explains the need for regular blood transfusions in the thalassemia major and S-β-thalassemia patients. Nearly all sickle cell anemia patients carried the β^s mutation on a chromosome with haplotype 19 (or Benin) and all had severe anemia with sickling complications. Identification of the β^S haplotype was through dot-blot analysis with oligonucleotide probes that detect mutations in the ^Gγ and ^Aγ promoter sequences, specific for this haplotype.