<unk>  can have different patterns of inheritance. Between 75% and 80% of cases are inherited in an autosomal recessive pattern, which means two copies of the gene in each cell are altered. Usually, each parent of an individual with autosomal recessive deafness is a carrier of one copy of the altered gene. These carriers do not have hearing loss. Another 20% to 25% of<unk>  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<unk>  tend to develop more severe hearing loss earlier in life than females who inherit a copy of the same gene mutation. Fathers will not pass X-linked traits to their sons since they do not pass on the X chromosome to their male offspring. Mitochondrial<unk> , which results from changes to the DNA in mitochondria, occurs in fewer than 1% of cases in the United States. The altered mitochondrial DNA is passed from a mother to her sons and daughters. This type of deafness is not inherited from fathers. Late onset progressive deafness is the most common neurological disability of the elderly. Although hearing loss of greater than 25 decibels is present in only 1% of young adults between the ages of 18–24 years of age, this increases to 10% in persons between 55–64 years of age and approximately 50% in octogenarians. 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<unk>  (Van Camp et al., 1997). Over forty genes associated with autosomal dominant<unk>  hearing loss have been localized and of these fifteen have been cloned. Genes related to<unk>  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<unk> , 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. The causes of<unk>  can be complex. Researchers have identified more than 30 genes that, when mutated, may cause<unk> ; however, some of these genes have not been fully characterized. Many genes related to deafness are involved in the development and function of the inner ear. Gene mutations interfere with critical steps in processing sound, resulting in hearing loss. Different mutations in the same gene can cause different types of hearing loss, and some genes are associated with both syndromic and<unk> . In many families, the gene(s) involved have yet to be identified. Deafness can also result from environmental factors or a combination of genetic and environmental factors, including certain medications, peri-natal infections (infections occurring before or after birth), and exposure to loud noise over an extended period. Types include: OMIM Gene Type DIAPH1 DFNA1 KCNQ4 DFNA2A GJB3 DFNA2B GJB2 DFNA3A GJB6 DFNA3B MYH14 DFNA4 DFNA5 DFNA5 TECTA DFNA8/12 COCH DFNA9 EYA4 DFNA10 MYO7A DFNA11, neurosensory COL11A2 DFNA13 POU4F3 DFNA15 MYH9 DFNA17 ACTG1 DFNA20/26 MYO6 DFNA22 SIX1 DFNA23 SLC17A8 DFNA25 GRHL2 DFNA28 TMC1 DFNA36 DSPP DFNA36, with dentinogenesis CCDC50 DFNA44 MYO1A DFNA48 MIR96 DFNA50 GJB2 DFNB1A GJB6 DFNB1B MYO7A DFNB2, neurosensory (see also Usher syndrome) MYO15A DFNB3 TMIE DFNB6 TMC1 DFNB7 TMPRSS3 DFNB8, childhood onset OTOF DFNB9 CDH23 DFNB12 STRC DFNB16 USH1C DFNB18 TECTA DFNB21 OTOA DFNB22 PCDH15 DFNB23 RDX DFNB24 GRXCR1 DFNB25 TRIOBP DFNB28 MYO3A DFNB30 WHRN DFNB31 ESRRB DFNB35 ESPN DFNB36 MYO6 DFNB37 HGF DFNB39 MARVELD2 DFNB49 COL11A2 DFNB53 PJVK DFNB59 LRTOMT DFNB63 LHFPL5 DFNB67 LOXHD1 DFNB77 TPRN DFNB79 PTPRQ DFNB84 SERPINB6 DFNB91 CABP2 DFNB93 PRPS1 DFNX1 POU3F4 DFNX2 MT-RNR1, COX1 deafness, aminoglycoside-induced (several mtDNA) DFN, sensorineural, mt
Nonsyndromic deafness
Cortical deafness
Post-lingual deafness
Prelingual deafness
Hearing loss with craniofacial syndromes
Surface dyslexia
Infantile esotropia
Vibroacoustic disease