Hearing loss can be inherited. Around 75–80% of all cases are inherited by recessive genes, 20–25% are inherited by dominant genes, 1–2% are inherited by X-linked patterns, and fewer than 1% are inherited by mitochondrial inheritance.
When looking at the genetics of deafness, there are 2 different forms, syndromic and nonsyndromic. Syndromic deafness occurs when there are other medical problems aside from deafness in an individual. This accounts for around 30% of deaf individuals who are deaf from a genetic standpoint. Nonsyndromic deafness occurs when there are no other problems associated with an individual other than deafness. From a genetic standpoint, this accounts for the other 70% of cases, which attributes to the vast majority of hereditary hearing loss. Syndromic cases occur with diseases such as Usher syndrome, Stickler, Waardenburg syndrome, Alport's Syndrome, and Neurofibromatosis type 2. These are diseases that have deafness as one of the symptoms or a common feature associated with it. The genetics that correspond with these various diseases are very complicated and are difficult to explain scientifically because the cause is unknown. In nonsyndromic cases where deafness is the only ‘symptom’ seen in the individual it is easier to pinpoint the physical genes.
Recent gene mapping has identified dozens of nonsyndromic dominant (DFNA#) and recessive (DFNB#) forms of deafness.
- The first gene mapped for non-syndromic deafness, DFNA1, involves a splice site mutation in the formin related homolog diaphanous 1 (DIAPH1). A single base change in a large *Costa Rican family was identified as causative in a rare form of low frequency onset progressive hearing loss with autosomal dominant inheritance exhibiting variable age of onset and complete penetrance by age 30.[PMID 9360932]
- The most common type of congenital hearing impairment in developed countries is DFNB1, also known as Connexin 26 deafness or GJB2-related deafness. GJB-2 related deafness accounts for over half of all recessive forms of deafness; and the most common GJB-2 deafness-associated mutation in Europeans is rs80338939.[PMID 18804553]
- The most common dominant syndromic forms of hearing impairment include Stickler syndrome and Waardenburg syndrome.
- The most common recessive syndromic forms of hearing impairment are Pendred syndrome, Large vestibular aqueduct syndrome and Usher syndrome.
- The congenital defect microtia can cause full or partial deafness depending upon the severity of the deformity and whether or not certain parts of the inner or middle ear are affected.
- Mutations in PTPRQ Are a Cause of Autosomal-Recessive Nonsyndromic Hearing Impairment.[PMID 20346435]
The paragraphs above are based on information in Wikipedia.
The tables below combine SNPedia data with data from the Hereditary Hearing Loss website, an excellent resource for detailed information.