The Heterozygous p.A684V Variant in the Gene Is a Mutational Hotspot Causing a Severe Hearing Loss Phenotype.

Background/objectives: A heterozygous mutation in the gene is responsible for autosomal dominant non-syndromic hearing loss (DFNA6/14/38) and Wolfram-like syndrome, which is characterized by bilateral sensorineural hearing loss with optic atrophy and/or diabetes mellitus. However, detailed clinical features for the patients with the heterozygous p.A684V variant remain unknown.

Methods: We report the clinical details of 14 cases with a heterozygous p.A684V variant in the gene identified from target resequencing analysis of 63 previously reported deafness genes by next-generation sequencing of 15,684 hearing loss patients (mean age 27.5 ± 23.1 years old, 6574 male, 8612 female and 498 for whom information was unavailable).

Results: Among the 14 patients from 13 families with the p.A684V variant, nine were sporadic cases. In addition, we confirmed de novo occurrence of this variant in seven families. This result strongly supports the notion that this variant was located on a mutational hotspot. When comparing previously reported cases of autosomal dominant gene-associated hearing loss, most of the patients in this study showed severe-to-profound bilateral sensorineural hearing loss (genotype-phenotype correlation). Two patients had optic atrophy, while the others did not have any other complications.

Conclusions: The identified heterozygous p.A684V variant appears to be a hotspot mutation and likely to cause severe-to-profound hearing loss in early childhood. Cochlear implantation is considered favorable in cases of hearing impairment due to this variant.