Homozygous mild beta-thalassaemia promoter transversion -71 C>T HBB:c.-121 C>T.

Beta-thalassaemia is one of the most common genetic disorders worldwide, which is caused by absent or decreased synthesis of beta-globin chain subunits. Beta-thalassaemias are diverse groups of disease with a wide spectrum of clinical phenotypes. The clinical phenotypes can include asymptomatic forms of beta-thalassaemia minor, intermediate and severe transfusion dependent beta-thalassaemia major. Clinical severity varies depending on the underlying β globin gene mutation. There are a number of mild β-thalassaemia gene defects that could be referred as a 'silent carrier'. Identifying the underlying molecular defect is essential to predict phenotype severity for optimal management, tailored treatment and improved quality of life.We report the first identification of a homozygous point mutation located within the promoter region of the β-globin gene at position -71 (C>T). The patient was a female child, who was referred to our clinic after she was found to have hypochromic microcytic anaemia with low haemoglobin (Hb) (67 g/L) and an Hb A level at the upper limit of the normal value (3.7%). This observation is a new example of homozygous mild β-thalassaemia with a borderline Hb A level, and illustrates a potential source of pitfall in the diagnosis of β-thalassaemia disease.