Hereditary and genetic deafness

Deafness can have many causes, from hair cell damage to a malformation of a part of the inner ear or damage to the auditory nerve. Is there a gene for deafness? Yes! Science has proved that it has been possible to find the gene responsible for this specific disease associated with a syndrome (deafness and pathology or malformation) in one hundred cases. These genes pass from parent to child when DNA is created, but some of them are recessive while others are dominant. Don’t forget that a dominant gene expresses itself more strongly, while a recessive gene must be linked to another recessive gene (father and mother) to be expressed.

Hereditary deafness: cases of transmission of a dominant gene

This occurs when a parent or sibling is affected.

Three syndromes have been identified:

Treacher Collings syndrome: deafness and deformity of the skull and face.
Branchio-oto-renal syndrome: deafness and deformity of the ear (outer, middle, or inner ear) and kidneys.
Waardenburg syndrome: deafness and disturbance of pigmentation (eyes, skin, hair, and hair growth).

For all these young patients, the degree of this disease varies according to the individual and the associated disorders. Some children have severe disease, while others have moderate hearing loss.

Genetic deafness: cases of transmission of a recessive gene

This occurs when both parents have perfect hearing and at least one child of the family is deaf.

Usher syndromes: progressive deafness and visual impairment.
Jervell and Lange-Nielsen syndrome: deafness and heart defects.
Pendred syndrome: deafness with malformation of the inner ear and thyroid abnormality.
Cockayne syndrome: deafness associated with 20% below average height and developmental delay.

Developments in genetics

Identifying the genetic mutations responsible for this specific disease is a recent area of research. These mutations affect genes that code for proteins involved in cochlear development or function. Genetic deafness is most often a single-gene disease, i.e., it involves the alteration of a single gene. One of them, DFNB1, discovered in 1997 by Christine Petit’s team at the Pasteur Institute’s Genetic Sensory Deafness Unit, is responsible for 50% of congenital deafness. Knowing these genes makes it possible to carry out molecular diagnoses and genetic counseling for the families concerned. In some cases, it also contributes to the choice of the rehabilitation method.

Gene therapy for hair cells

Scientists are looking at regenerating damaged hair cells through gene therapy. Promising results have already been obtained in the avian cochlea. The idea is to derive new, functional hearing cells from support cells that remain after the death of the hair cells.

Tech improvements

Technological developments are expected to improve the performance of hearing aids and implants. Today, cochlear implant patients have great difficulty with multiple sound sources or complex sounds such as music. Researchers are experimenting on increasing the number of electrodes, the number of electrical pulses per second or by considering rapid changes in frequency.