A novel mechanism for thalassaemia intermedia

Thalassaemia intermedia is a moderate form of thalassaemia resulting from various genetic defects. We report an undescribed mechanism leading to this condition: a somatic deletion of the β-globin gene in the haemopoietic lineage of a heterozygous β-thalassaemic patient. We did molecular studies and haemoglobin analysis of the patient and his parents. We found that the deletion gives rise to a mosaic of cells with either one or no functional β-globin gene and it extends to a region of frequent loss of heterozygosity called LOH11A, which is located close to the β-globin locus. Thus, loss of heterozygosity can be a cause of non-malignant genetic disease.