HBB: c.316-125A>G and HBB: c.316-42delC: Phenotypic Evaluations of Two Rare Changes in the Second Intron of the HBB Gene

Abstract

We report two very rare changes in the second intron of the HBB gene, a substitution at nucleotide (nt) 726 [IVS-II-726 (A>G) (β+), NM_000518, HBB: c.316-125A>G] and a deletion of a cytosine at nt 809 [IVS-II-809 (–C) (β), NM_000518, HBB: c.316-42delC] identified during the screening program for hemoglobinopathies in the resident Sicilian population. The purpose of this study was to evaluate the clinical implication of these rare changes, particularly in coinheritance with known mutations in the globin clusters, in order to conduct an appropriate genetic counseling for at-risk couples. Molecular analysis detected the first rare nt substitution in two cases in simple heterozygosity and in two cases in association with other known mutations on globin genes, while the deletion was identified in a pregnant woman, carrier of β-thal, and in her fetus at prenatal diagnosis (PND) for hemoglobinopathies. The present study emphasizes the importance of sharing the observed changes in the globin gene cluster, especially in the case of new or rare undefined mutations, in order to facilitate the determination of their phenotypic expression and possible interactions with known molecular defects.