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Keywords:

  • a-thalassaemia non-deletional type;
  • Hb Tunis-Bizerte;
  • unstable a-globin variants;
  • ax globin gene;
  • microcytosis

A Leu– Pro substitution at position 129 of the ci globin gene was detected in three members of a Tunisian family by sequencing the whole a2 and i DNA. The mutation was verified by dot-blot allele-specific hybridization as well as by digestion of PCR and RT-PCR products with Nci I, since the aj129T_>c mutation creates an additional recognition site for the above-mentioned enzyme. The Q,ii29(Hi2)Leupro substitution disturbs helix H resulting in a-thal trait most probably because the unstable a-globin chain variant cannot form a/3 dimers. A search for the abnormal Hb and for the abnormal a globin chain by isoelectric focusing, carboxymethyl cellulose chromatography and electrospray ionization mass spectrometry was negative. In the heterozygous state, the Qii29(Hi2) Leu-Pro varjant is manifested by microcytosis (MCV73fl), whereas in the homozygous state there is moderate anaemia with marked microcytosis (Hb 11–6 g/dl, MCV 65 fl).