Genotype-phenotype correlations for SLC26A4-related deafness

Area of Science:

• Genetics
• Otolaryngology
• Molecular Biology

Background:

• Pendred syndrome (PS) and non-syndromic enlarged vestibular aqueduct (EVA) are inherited disorders causing sensorineural hearing loss (SNHL) and inner ear malformations.
• Mutations in the SLC26A4 gene, encoding the protein pendrin, are associated with the pathophysiology of these conditions.

Purpose of the Study:

• To investigate the correlation between SLC26A4 genotypes and the complexity and severity of phenotypes in PS and EVA spectrum disorders.
• To analyze the genetic heterogeneity and its relationship with phenotypic presentation in patients with SNHL and inner ear abnormalities.

Main Methods:

• Ascertainment of 1,506 deaf patients with sensorineural hearing loss.
• Screening for SLC26A4 mutations in patients with and without inner ear abnormalities.
• Statistical comparison of SLC26A4 genotype distribution across different phenotypes (PS, EVA, Mondini Dysplasia).

Main Results:

• Inner ear abnormalities were identified in 32% of the studied patients.
• SLC26A4 mutations were detected in 35% of patients (two mutations in 16%, one mutation in 19%).
• Statistically significant differences in genotype distribution were observed between PS and EVA-Mondini patients (P = 0.005) and between EVA and Mondini patients (P = 0.0003).

Conclusions:

• A correlation exists between the complexity of inner ear malformations and genetic heterogeneity.
• Pendred syndrome exhibits the most severe phenotype and homogeneous etiology, while EVA shows the least severe phenotype and most heterogeneous etiology.
• The variability in hearing loss suggests that other genetic and/or environmental factors contribute to the pathogenesis of the PS-Mondini-EVA disease spectrum.