Dominant Beta-Thalassaemia With Unusually High Hb A(2) And Hb F Caused By Beta(Cd121(-G)) (Hbb:C.364delg) In Exon 3 Of Beta-Globin Gene

We describe a dominant beta -thalassaemia caused by a deletion of G at nucleotide position 364 in exon 3 of the beta -globin gene. The heterozygosity of this mutation was found in a 36-year-old Thai patient who had moderate hypochromic microcytic anaemia with haemolytic blood picture. Haemoglobin (Hb) analysis revealed relatively higher Hbs A(2) (6.8%) and F (4.7%) as compared with those of beta (0)-thalassaemia (n=278) and beta (+)-thalassaemia (n=55) carriers in our series. Secondary structure prediction of the elongated beta -globin chain showed that the alpha -helix at the C-terminal is disrupted dramatically by the random coil and beta -sheet, which should result in a highly unstable beta -globin variant, undetectable in peripheral blood and a dominant clinical phenotypic feature.