Recessive LOXHD1 Variants Cause a Milder Prelingual Hearing Loss: Genotype-Phenotype Correlation and Three Additional Patients With Novel Variants

Abstract

BackgroundBiallelic mutations in LOXHD1 have been identified as the cause of DFNB77 (deafness, autosomal recessive 77). It is a novel, progressive, severe-profound, and late-onset non-syndromic hearing loss, and is genetically and phenotypically highly heterogeneous. This study aimed to provide an additional three cases of DFNB77 to analyze this complex disease.MethodsWe presented three cases of pediatric patients with prelingual milder form of the DFNB77 with residual hearing at low frequencies. Trio whole-exome sequencing (WES) was conducted to identify the pathogenic variants. Additionally, we reviewed the literature to further analyze the relationships between the genotype and audiology phenotype of LOXHD1 worldwide.ResultsSix novel possible pathogenic LOXHD1 variants in three patients were identified by WES, including three missense, one nonsense, and two splicing variants. The literature review showed that 68.5% of DFNB77 patient onset before five years old; Most variants (60%) were associated with a milder phenotype, particularly variants in the protein domain of PLAT 7 and PLAT 9. We found that compared with homozygous LOXHD1 variants, individuals with heterozygous compound variants had a significantly milder phenotype, especially individuals carrying one missense and one splicing or bi-allelic missense variants (P <0.05). Audiometric analysis at different ages showed that the hearing loss degree was aggravated at all frequencies in adulthood and more severe in elderhood.ConclusionsWe report three children with hearing loss carrying six novel LOXHD1 variants identified by WES. Furthermore, our work indicates that DFNB77 may be milder than previously reported, and recommends considering the genotype combination and mutation location of LOXHD1 and race-specificity in DFNB77 molecular diagnoses and management.