Nonsyndromic deafness constitutes 75% of all hearing loss cases, and an estimated 100 genes are thought to be linked to this condition.
Mitochondrial nonsyndromic deafness involves changes to the small amount of DNA found in mitochondria, the energy-producing centers within cells.
[3] Most forms of nonsyndromic deafness are associated with permanent hearing loss caused by damage to structures in the inner ear.
Another 20% to 25% of nonsyndromic deafness cases are autosomal dominant, which means one copy of the altered gene in each cell is sufficient to result in hearing loss.
People with autosomal dominant deafness most often inherit an altered copy of the gene from a parent who has hearing loss.
Between 1% and 2% of cases show an X-linked pattern of inheritance, which means the mutated gene responsible for the condition is located on the X chromosome.
Males with X-linked nonsyndromic deafness tend to develop more severe hearing loss earlier in life than females who inherit a copy of the same gene mutation.
Mitochondrial nonsyndromic deafness, which results from changes to the DNA in mitochondria, occurs in fewer than 1% of cases in the United States.
The relative contribution of heredity to age-related hearing impairment is not known, however, the majority of inherited late-onset deafness is autosomal dominant and non-syndromic (Van Camp et al., 1997).
Mutations in the ACTG1, CABP2, CDH23, CLDN14, COCH, COL11A2, DFNA5, ESPN, EYA4, GJB2, GJB6, KCNQ4, MYO15A, MYO6, MYO7A, OTOF, PCDH15, POU3F4, SLC26A4, STRC, TECTA, TMC1, TMIE, TMPRSS3, USH1C, and WFS1 genes cause nonsyndromic deafness, with weaker evidence currently implicating genes CCDC50, DIAPH1, DSPP, ESRRB, GJB3, GRHL2, GRXCR1, HGF, LHFPL5, LOXHD1, LRTOMT, MARVELD2, MIR96, MYH14, MYH9, MYO1A, MYO3A, OTOA, PJVK, POU4F3, PRPS1, PTPRQ, RDX, SERPINB6, SIX1, SLC17A8, TPRN, TRIOBP, SLC26A5, and WHRN.
Types include: The diagnosis of nonsyndromic deafness involves a comprehensive assessment to determine the cause of hearing loss in an individual without associated syndromic features.