High Frequency of <i>AIFM1</i> Variants and Phenotype Progression of Auditory Neuropathy in a Chinese Population

Abstract

To decipher the genotype-phenotype correlation of auditory neuropathy (AN) caused by <i>AIFM1</i> variations, as well as the phenotype progression of these patients, exploring the potential molecular pathogenic mechanism of AN. A total of 36 families of individuals with AN (50 cases) with <i>AIFM1</i> variations were recruited and identified by Sanger sequencing or next-generation sequencing; the participants included 30 patients from 16 reported families and 20 new cases. We found that <i>AIFM1</i>-positive cases accounted for 18.6% of late-onset AN cases. Of the 50 AN patients with <i>AIFM1</i> variants, 45 were male and 5 were female. The hotspot variation of this gene was p.Leu344Phe, accounting for 36.1%. A total of 19 <i>AIFM1</i> variants were reported in this study, including 7 novel ones. A follow-up study was performed on 30 previously reported <i>AIFM1-</i>positive subjects, 16 follow-up cases (53.3%) were included in this study, and follow-up periods were recorded from 1 to 23 years with average 9.75 ± 9.89 years. There was no hearing threshold increase during the short-term follow-up period (1-10 years), but the low-frequency and high-frequency hearing thresholds showed a significant increase with the prolongation of follow-up time. The speech discrimination score progressed gradually and significantly along with the course of the disease and showed a more serious decline, which was disproportionately worse than the pure tone threshold. In addition to the X-linked recessive inheritance pattern, the X-linked dominant inheritance pattern is also observed in <i>AIFM1</i>-related AN and affects females. In conclusion, we confirmed that <i>AIFM1</i> is the primary related gene among late-onset AN cases, and the most common recurrent variant is p.Leu344Phe. Except for the X-linked recessive inheritance pattern, the X-linked dominant inheritance pattern is another probability of <i>AIFM1</i>-related AN, with females affected. Phenotypical features of <i>AIFM1</i>-related AN suggested that auditory dyssynchrony progressively worsened over time.