A First Clinical and Molecular Study of Rare IVS-II-806 (G > C) (HBB:c.316-45G > C) Variant in the β-globin Gene: A Possibly Benign Variant.

Abstract

β-thalassemia is a common genetic disease affecting a single gene, disease with a high incidence in South China. We hereby, aim to provide the clinical and hematological features of a rare β-globin gene variant in the Chinese population. Ten subjects from three unrelated Chinese families were enrolled in this study. Hematological analysis and thalassemia gene testing were preformed to screen for common α and β-thalassemia variants. Gap-polymerase chain reaction (Gap-PCR) and DNA sequencing were utilized to examine the rare or novel thalassemia variants. Six cases were identified carrying the rare IVS-II-806 (G > C) (HBB:c.316-45G > C) variant in the β-globin gene. The proband in family 1 carry three rare β-globin gene mutations including CD39 (C > T), IVS-II-81 (C > T) and IVS-II-806 (G > C) combined with a --SEA/αα deletion, exhibiting the β-thalassemia trait. Further pedigree investigation indicated that the genotype of the proband in family 1 was --SEA/αα, βCD39 (C>T), IVS-II-81(C>T)/βIVS-II-806(G>C). Meanwhile, the twin girls in family 1 carrying the IVS-II-806 (G > C) mutation demonstrated a normal hematological phenotype. In family 2, the proband and his sister carry the IVS-II-806 (G > C) mutation, eliciting high levels of Hb A2 and slightly low levels of MCV and MCH. Moreover, the proband in family 3 carrying the same mutation exhibited a slightly low MCV level as well. In this study, clinical and hematological analysis of the IVS-II-806 (G > C) mutation was first conducted within the Chinese population, with results indicating that it may be a benign variant.