[Delta⁰-thalassemia by insertion of 27 base pairs in δ-globin gene with decreased hemoglobin A₂ levels]

BACKGROUND AND OBJECTIVE

We describe a novel delta-thalassemia mutation causing decreased hemoglobin (Hb) A2 levels associated with Hb Watts, variant Hb resulting from a trinucleotide deletion in Spain.

PATIENTS AND METHOD

Hb variant analysis was performed by cation-exchange high performance liquid chromatography (HPLC) and capillary zone electrophoresis. Polymerase chain reaction and DNA sequence analyses were used to identify mutations in the δ- and α-globin genes.

RESULTS

Abnormal Hb was observed on capillary zone electrophoresis in Z6 and by cation-exchange HPLC a slower peak than HbA was observed at an retention time of 4.19min. This variant Hb is called Hb Watts [α2 74(EF3)Asp->0 or α2 75(EF4)Asp->0; HBA2:c.226_228delGAC]. The decreased HbA2 percentage owes to an insertion of 27nt between nt 83 and 84 of IVS-I of the δ-globin gene.

CONCLUSIONS

When analyzing a chromatogram, the possibility of the existence of delta-thalassemia or an HbA2 variant should be considered, apart from alfa-, beta-thalassemia and structural haemoglobinopathies. To this end, each of the peaks and their percentages should be considered to allow for correct interpretation and to avoid misdiagnosis as much as possible.