δ-Thalassemia with Complete Absence of Hb A2 in a Chinese Family.

A Chinese family with δ-thalassemia (δ-thal) was found, in which the daughter is homozygous for δ-thal (HBD: c.-127T>C) with complete deficiency of Hb A2 and the mother is a heterozygote with low level of Hb A2. The father, however, is a heterozygote with a normal Hb A2 value due to coinheritance of a ß-thalassemia (ß-thal). Although no abnormal clinical or hematological findings were noted in the individuals with δ-thal, one should keep in mind that ß-thal can be missed during routine preliminary screening when ß-thal and δ-thal coexist in a subject.

Delta globin gene variations leading to reduction in HbA2 levels.

INTRODUCTION: Mutations in the δ-globin gene are not pathogenically relevant, but co-inheritance of δ-globin variants along with ß-globin gene defects can mask the diagnosis of ß-thalassaemia trait. METHODS: Routine haematological parameters were carried out. Molecular analysis of ß-globin gene mutations was carried out by CRDB, ARMS and DNA sequencing. δ- globin gene analysis was carried out by DNA sequencing. RESULTS: In this case study, we report a ß-thalassaemia trait (IVS 1-5G→C) (HBB:c.92 + 5G→C) with HbA2 of 1% showing the presence of δ-globin gene variant HbA2 St. George CD 81 (C→T) (HBD:c.244C→T). A similar observation was reported in another unrelated patient who showed near absence of HbA2 level in HPLC. He showed a presence of δ-globin gene mutation HbA2 Saurashtra CD 100(C→T) (HBD: c.301C→T) and a single 3.7 kb deletion in the α-globin gene. CONCLUSION: In the countries, where ß-thalassaemia is prevalent, an awareness and detection of different δ-globin gene mutations is important, as complex interactions between these haemoglobinopathies can lead to the misdiagnosis of ß-thalassaemia carriers.