About 1 in 1,000 children in the United States is born with profound deafness. By age 9, about 3 in 1,000 children have hearing loss that affects the activities of daily living. More than half of these cases are caused by genetic factors. Most cases of genetic deafness (70% to 80%) are nonsyndromic; the remaining cases are caused by specific genetic syndromes. In adults, the chance of developing hearing loss increases with age; hearing loss affects half of all people older than 80 years.

The recurrence of DOOR in siblings and the finding of DOOR syndrome in a few families with consanguinity suggest that the condition is an autosomal recessive genetic condition. Mutations in TBC1D24 have been identified in 9 families.

The actual incidence of this disease is not known, but only 243 cases have been reported in the scientific literature, suggesting an incidence of on the order of one affected person in ten million people.

The frequency is unknown, but the disease is considered to be very rare.

These are much more common in premature babies, particularly those under 1500 g at birth. Premature birth can be associated with problems that result in sensorineural hearing loss such as anoxia or hypoxia(poor oxygen levels), jaundice, intracranial haemorrhages, meningitis. Fetal alcohol syndrome is reported to cause hearing loss in up to 64% of infants born to alcoholic mothers, from the ototoxic effect on the developing fetus, plus malnutrition during pregnancy from the excess alcohol intake.

The first symptom is typically diabetes mellitus, which is usually diagnosed around the age of 6. The next symptom to appear is often optic atrophy, the wasting of optic nerves, around the age of 11. The first signs of this are loss of colour vision and peripheral vision. The condition worsens over time, and people with optic atrophy are usually blind within 8 years of the first symptoms. Life expectancy of people suffering from this syndrome is about 30 years.

Some over-the-counter as well as prescription drugs and certain industrial chemicals are ototoxic. Exposure to

these can result in temporary or permanent hearing loss.

Some medications cause irreversible damage to the ear, and are limited in their use for this reason. The most important group is the aminoglycosides (main member gentamicin). A rare mitochondrial mutation, m.1555A>G, can increase an individual's susceptibility to the ototoxic effect of aminoglycosides. Long term hydrocodone (Vicodin) abuse is known to cause rapidly progressing sensorineural hearing loss, usually without vestibular symptoms. Methotrexate, a chemotherapy agent, is also known to cause hearing loss. In most cases hearing loss does not recover when the drug is stopped. Paradoxically, methotrexate is also used in the treatment of autoimmune-induced inflammatory hearing loss.

Various other medications may reversibly degrade hearing. This includes loop diuretics, sildenafil (Viagra), high or sustained dosing of NSAIDs (aspirin, ibuprofen, naproxen, and various prescription drugs: celecoxib, etc.), quinine, and macrolide antibiotics (erythromycin, etc.).

Prolonged or repeated environmental or work-related exposure to ototoxic chemicals can also result in sensorineural hearing loss. Some of these chemicals are:

- butyl nitrite - chemical used recreationally known as 'poppers'

- carbon disulfide - a solvent used as a building block in many organic reactions

- styrene, an industrial chemical precursor of polystyrene, a plastic

- carbon monoxide, a poisonous gas resulting from incomplete combustion

- heavy metals: tin, lead, manganese, mercury

- hexane, an industrial solvent and one of the significant constituents of gasoline

- ethylbenzene, an industrial solvent used in the production of styrene

- toluene and xylene, highly poisonous petrochemical solvents. Toluene is a component of high-octane gasolne; xylene is used in the production of polyester fibers and resins.

- trichloroethylene, an industrial degreasing solvent

- Organophosphate pesticides

The clinical course of BVVL can vary from one patient to another. There have been cases with progressive deterioration, deterioration followed by periods of stabilization, and deterioration with abrupt periods of increasing severity.

The syndrome has previously been considered to have a high mortality rate but the initial response of most patients to the Riboflavin protocol are very encouraging and seem to indicate a significantly improved life expectancy could be achievable. There are three documented cases of BVVL where the patient died within the first five years of the disease. On the contrary, most patients have survived more than 10 years after the onset of their first symptom, and several cases have survived 20–30 years after the onset of their first symptom.

Families with multiple cases of BVVL and, more generally, multiple cases of infantile progressive bulbar palsy can show variability in age of disease onset and survival. Dipti and Childs described such a situation in which a family had five children that had Infantile PBP. In this family, three siblings showed sensorineural deafness and other symptoms of BVVL at an older age. The other two siblings showed symptoms of Fazio-Londe disease and died before the age of two.

Presence of inner ear abnormalities lead to Delayed gross development of child because of balance impairment and profound deafness which increases the risk of trauma and accidents.

- Incidence of accidents can be decreased by using visual or vibrotactile alarm systems in homes as well as in schools.

- Anticipatory education of parents, health providers and educational programs about hazards can help.

There is no known direct treatment. Current treatment efforts focus on managing the complications of Wolfram syndrome, such as diabetes mellitus and diabetes insipidus.

DOOR (deafness, onychdystrophy, osteodystrophy, and mental retardation) syndrome is a genetic disease which is inherited in an autosomal recessive fashion. DOOR syndrome is characterized by mental retardation, sensorineural deafness, abnormal nails and phalanges of the hands and feet, and variable seizures. A similar deafness-onychodystrophy syndrome is transmitted as an autosomal dominant trait and has no mental retardation. Some authors have proposed that it may be the same as Eronen Syndrome, but since both disorders are extremely rare it is hard to make a determination.

Tietz syndrome, also called Tietz albinism-deafness syndrome or albinism and deafness of Tietz, is an autosomal dominant congenital disorder characterized by deafness and leucism. It is caused by a mutation in the microphthalmia-associated transcription factor (MITF) gene. Tietz syndrome was first described in 1963 by Walter Tietz (1927–2003) a German Physician working in California.

Björnstad syndrome is an autosomal recessive congenital condition involving pili torti and nerve deafness and hair abnormalities.

It was first characterized in 1965, in Oslo, by prof. Roar Theodor Bjørnstad (1908–2002).

It has been mapped to BCS1L. Hearing disabilities related to Björnstad syndrome are congenital, and the severity of the deafness varies from person to person. Pili torti is recognized in early childhood and is characterised by twisted hair shafts and brittle hair.

Nonsyndromic deafness is hearing loss that is not associated with other signs and symptoms. In contrast, syndromic deafness involves hearing loss that occurs with abnormalities in other parts of the body. Genetic changes are related to the following types of nonsyndromic deafness.

- DFNA: nonsyndromic deafness, autosomal dominant

- DFNB: nonsyndromic deafness, autosomal recessive

- DFNX: nonsyndromic deafness, X-linked

- nonsyndromic deafness, mitochondrial

Each type is numbered in the order in which it was described. For example, DFNA1 was the first described autosomal dominant type of nonsyndromic deafness. Mitochondrial nonsyndromic deafness involves changes to the small amount of DNA found in mitochondria, the energy-producing centers within cells.

Most forms of nonsyndromic deafness are associated with permanent hearing loss caused by damage to structures in the inner ear. The inner ear consists of three parts: a snail-shaped structure called the cochlea that helps process sound, nerves that send information from the cochlea to the brain, and structures involved with balance. Loss of hearing caused by changes in the inner ear is called sensorineural deafness. Hearing loss that results from changes in the middle ear is called conductive hearing loss. The middle ear contains three tiny bones that help transfer sound from the eardrum to the inner ear. Some forms of nonsyndromic deafness involve changes in both the inner ear and the middle ear; this combination is called mixed hearing loss.

The severity of hearing loss varies and can change over time. It can affect one ear (unilateral) or both ears (bilateral). Degrees of hearing loss range from mild (difficulty understanding soft speech) to profound (inability to hear even very loud noises). The loss may be stable, or it may progress as a person gets older. Particular types of nonsyndromic deafness often show distinctive patterns of hearing loss. For example, the loss may be more pronounced at high, middle, or low tones.

Nonsyndromic deafness can occur at any age. Hearing loss that is present before a child learns to speak is classified as prelingual or congenital. Hearing loss that occurs after the development of speech is classified as postlingual.

Michel aplasia, also known as complete labyrinthine aplasia (CLA), is a congenital abnormality of the inner ear. It is characterized by the bilateral absence of differentiated inner ear structures and results in complete deafness (anacusis).

Michel aplasia should not be confused with michel dysplasia. It may affect one or both ears.

"Aplasia" is the medical term for body parts that are absent or do not develop properly. In Michel aplasia, the undeveloped (anaplastic) body part is the bony labyrinth of the inner ear. Other nearby structures may be underdeveloped as well.

The disorder has been associated with various mutations in the SLC52A2 and "SLC52A3" genes. This gene is thought to be involved in transport of riboflavin.

BVVL is allelic and phenotypically similar to Fazio–Londe disease and likewise is inherited in an autosomal recessive manner.

The overall incidence is ~1/42,000 to 1/50,000 people. Types I and II are the most common types of the syndrome, whereas types III and IV are rare. Type 4 is also known as Waardenburg‐Shah syndrome (association of Waardenburg syndrome with Hirschsprung disease).

Type 4 is rare with only 48 cases reported up to 2002.

About 1 in 30 students in schools for the deaf have Waardenburg syndrome. All races and sexes are affected equally. The highly variable presentation of the syndrome makes it difficult to arrive at precise figures for its prevalence.

Weissenbacher-Zweymüller syndrome affects males and females in the same numbers. About 30 cases have been reported in medical literature. This disorder can be underdiagnosed causing no true frequency in the population. Only 30 cases have been reported in medical literature.

ODD is typically an autosomal dominant condition, but can be inherited as a recessive trait. It is generally believed to be caused by a mutation in the gene GJA1, which codes for the gap junction protein connexin 43. Slightly different mutations in this gene may explain the different way the condition manifests in different families. Most people inherit this condition from one of their parents, but new cases do arise through novel mutations. The mutation has high penetrance and variable expression, which means that nearly all people with the gene show signs of the condition, but these signs can range from very mild to very obvious.

Worth syndrome is caused by a mutation in the LRP5 gene, located on human chromosome 11q13.4. The disorder is inherited in an autosomal dominant fashion. This indicates that the defective gene responsible for a disorder is located on an autosome (chromosome 11 is an autosome), and only one copy of the defective gene is sufficient to cause the disorder, when inherited from a parent who has the disorder.

Autosomal dominant porencephaly type I is rare and its prevalence and incidence are unknown. It affects males and females equally.

Dominant genetic disorders can be caused by just a single copy of an abnormal gene. This abnormal gene can be the result of being inherited from either parent or be a new mutation. Most cases are caused by a de novo (new) mutation in the gene that occurs during the formation of the egg or sperm. These cases occur when there is no history of the disorder in the family.

The COL11A2 gene is responsible for providing instructions on making one component of the type XI collagen. Type XI collagen is a complex molecule that helps give structure and strength to the connective tissues. Collagen is found in bone. It is also found in cartilage that makes up most of the skeleton during early development. The mutation of COL11A2 in Weissenbacher-Zweymüller syndrome disrupts the assembly of the type XI collagen molecules. The malfunctioning collagen weakens the connective tissue causing impaired bone development.

COL11A2 is also associated with autosomal dominant non-syndromic hearing loss (ADNSHL). All mutations of COL11A2 in ADNSHL are missense mutations.

Genetic factors are thought to cause more than 50% of all incidents of congenital hearing loss. Genetic hearing loss may be autosomal dominant, autosomal recessive, or X-linked (related to the sex chromosome).

If the Hirschsprung's disease is treated in time, ABCD sufferers live otherwise healthy lives. If it is not found soon enough, death often occurs in infancy. For those suffering hearing loss, it is generally regressive and the damage to hearing increases over time. Digestive problems from the colostomy and reattachment may exist, but most cases can be treated with laxatives. The only other debilitating symptom is hearing loss, which is usually degenerative and can only be treated with surgery or hearing aids.

Myhre syndrome is a rare genetic disorder inherited in an autosomal dominant fashion. It is caused by mutation in SMAD4 gene.