Hearing loss phenotypes in Alport syndrome: experience in a tertiary referral center

Background: Despite previous reports of auditory phenotypes in Alport syndrome (AS), there have been no studies specifically addressing audiological phenotypes in South Korea. Herein, we elaborated on the audiological characteristics associated with AS based on their genotypes.

Methods: We reviewed data from in-house AS patients between March 2014 and February 2023, excluding those without audiological documentation or genetic diagnoses. We retrieved medical history, hearing level, estimated glomerular filtration rate (eGFR), and genotypes from their medical records. The natural course of hearing loss and correlations between audiogram and eGFR were evaluated according to audio-gene profiles.

Results: Our study included 49 AS patients from 47 families, identifying 60 disease-causing variants, 45 of which were novel. All variants were classified as pathogenic or likely pathogenic based on ACMG-AMP guidelines. The auditory phenotypes of autosomal recessive AS (ARAS) and male X-linked AS (XLAS) patients demonstrated a progressive nature, with a down-sloping configuration. The ARAS with truncated variants exhibited an earlier onset of hearing loss than those with non-truncated variants. In male XLAS patients, the presence of truncated allele linked to more rapid hearing deterioration across all frequencies. In both ARAS and male XLAS patients, the presence of truncated allele was significantly associated with hearing severity and eGFR. Conversely, the majority of female XLAS and autosomal dominant AS maintained normal hearing levels without any correlation of eGFR, regardless of genotypes.

Conclusion: This study detailed the auditory phenotypes and the auditory-renal association of AS at a tertiary center in South Korea, providing valuable references that guide auditory testing and rehabilitation strategies.