Genetic hearing loss can be present at birth (congenital) or develop later in life (acquired).
There are two forms of genetic hearing loss: syndromic and non-syndromic.
Syndromic means that the hearing loss occurs in conjunction with other clinical findings, such as malformations of the ear or abnormalities of other organ systems.
Non-syndromic means that the hearing loss is the only clinical finding and there are no other related medical problems. Non-syndromic genetic hearing loss is much more common than syndromic.
Genetic hearing loss can be broken down further into autosomal recessive inheritance (about 75% of cases), autosomal dominant inheritance (about 15% of cases) and other inheritance (X-linked and Mitochondrial).
Recessive inheritance means that the child’s parents are carriers of the gene in question, but are not affected by the impairment themselves.The gene Connexin 26 (CX26) is known to be responsible for 50% of the cases of recessive inheritance. There is a 25% chance that a child of two carriers will have hearing loss.
Syndromes such as Usher, Pendred, Jervell and Lange-Nielsen have an autosomal recessive inheritance.
Dominant inheritance means that a single copy of the mutated gene of hearing loss is needed to cause the impairment. One parent is usually affected by the impairment and there is a 50% chance that the child will have hearing loss.
Syndromes such as Waardenburg, Branchio-Oto-Renal, Stickler, and Treacher-Collins have an autosomal dominant inheritance pattern.
X-linked inheritance is a mutation of the gene on the X chromosome that affects males more severly than females. Syndromes such as Alport have a X-linked inheritance.
Mitochondrial inheritance comes from the mother, through a defect in the mitochondria DNA.
How is genetic hearing loss diagnosed?
Genetic testing can be used to diagnose whether the hearing loss is caused by a genetic factor. Genetic testing is limited, but will most likely become routine for many genes associated with hearing loss in the near future.
How is it treated?
Genetic hearing loss will be treated depending on the type and degree of the hearing loss. Surgical treatments may be used for certain conductive and mixed genetic hearing loss, as well as hearing devices and implantable devices for rehabilitation of all types of hearing loss.
The future of genetic testing will help to determine whether the hearing loss is syndromic or non-syndromic, which may guide the rehabilitation method used for management of the hearing loss.
Does genetic hearing loss cause lasting problems?
If left untreated or managed, genetic hearing loss can cause significant speech and language delays in a child, and communication difficulties later in life.