Clinical data analysis of genotypes and phenotypes of deafness gene mutations in newborns: A retrospective study

We retrospectively analyzed newborns with deafness gene mutations and summarized the relationship between genotype and phenotype to provide a basis for genetic counseling. We studied 582 subjects positive for deafness gene mutations that were treated in the otology outpatient department of Beijing Tongren Hospital, Capital Medical University, between April 2012 and April 2016. The subjects were divided into 3 categories: a diagnosed group (group A), which was further subdivided into subgroups A1 (homozygous and compound heterozygous GJB2 mutations) and A2 (homozygous and compound heterozygous SLC26A4 mutations); a drug-induced deafness group (group B, mitochondrial (Mt) gene mutations); and a mutation carrier group (group C), which was further subdivided into the subgroups C1 (GJB2 heterozygous mutations), C2 (SLC26A4 heterozygous mutations), C3 (GJB3 heterozygous mutations), and C4 (double gene mutations). Partial sequences positive for GJB2 or SLC26A4 were sequenced and analyzed for mutations. Subjects underwent otoscopic examination and comprehensive audiological evaluation, and temporal bone computerized tomography and/or inner ear magnetic resonance imaging were performed. GJB2 235delC was the most common mutation locus. The highest proportion of deafness detected during universal newborn hearing screening was for drug-induced deafness, whereas the lowest was for the diagnosed group. GJB2 gene mutations mainly resulted in flat-type, profound-to-severe sensorineural hearing loss (SNHL). SLC26A4 gene mutation was mainly associated with high-frequency drop-type and profound-severe SNHL and was closely related to enlargement of the vestibular aqueduct.