Combination of Hb Knossos [Cod 27 (G-T)] and IVSII-745 (C-G) in a Turkish patient with beta-thalassemia major

Hb Knossos (HBB: c.82G > T), β-globin CD 5 (-CT) (HBB: c.17_18delCT) and δ-globin CD 59 (-a) (HBD: c.179delA) mutations in a Syrian patient with β-thalassemia intermedia

Background

Beta thalassemia (β-thal) is an inherited hemoglobin disorder characterized by reduced synthesis of the hemoglobin that results in microcytic hypochromic anemia. β-Thalassemia intermedia (TI) is a clinical term of intermediate gravity between the carrier state and β-thalassemia major (β -TM).

Case presentation

We describe a 12-year-old male proband originating from Al-Quneitra province - southwest Syria. Hematological investigations revealed, pallor and anemia (Hb 9 g/dl). The mean cell volume (MCV) 64 fL; mean cell hemoglobin (MCH) 21.8 pg. Capillary electrophoresis (CE) electropherogram revealed low level of Hb A1 (36.2%), high level of Hb F (62.2%) and low level of Hb A2 (1.6%). The proband requires blood transfusion occasionally. Direct DNA sequencing and Polymerase chain reaction-restriction fragment length polymorphism (PCR/RFLP) for mutations detection were used. The molecular analysis revealed the presence of rare β⁺ Hb Knossos codon 27 (G > T) (HBB: c.82G > T) variant associated with β⁰ codon 5 [−CT] (HBB: c.17_18delCT) mutation in beta-globin (β-globin) gene and δ⁰ codon 59 [−A] (HBD: c.179delA) mutation in delta-globin (δ-globin) gene. The proband tested negative for the common deletional forms of alpha thalassemia (α-thal). Polymorphism of the Xmn-I locus (HBG2: c.-211C > T) revealed that the proband had a homozygous [TT] for Xmn-1 locus.

Conclusions

To our knowledge, this is the first report of beta thalassemia intermedia due to combination of Hb Knossos /codon 5 [−CT] associated with δ⁰ codon 59 [−A] in Syrian patient. On the other hand, in Syria, β-thal carriers who have low level of Hb A2 due to decreased δ-chain production, different δ-thal gene mutations must be screened to avoid the failure diagnosis of β-thal disease.

Hb Knossos: HBB:c.82G>T Associated with HBB:c.315+1G>A Beta Zero Mutation Causes Thalassemia Intermedia

β-thalassemia is the most common single gene disorder worldwide and in Iran. In the present study we report for the first time a rare variant of hemoglobin HBB:c.82G>T; Codon 27 GCC→TCC (Ala→Ser), Hb Knossos, using sequencing and reverse dot blot hybridization, in members of a family from North Iran. The family has a 16 years-old compound heterozygous thalassemia intermedia male child presenting this variant together with HBB:c.315+1G>A (IVSII-I) mutation. The father, heterozygous for Hb Knossos, showed borderline hematological indices. To our knowledge, this is the first report of Hb Knossos in trans with the β(O) IVSII-I allele leading to thalassemia intermedia. Our data also highlight the necessity of deep molecular characterization of subjects presenting normal HbA2 level associated with abnormal or borderline red cell indices.