Clinical features: Congenital sensorineural deafness is most commonly isolated (80%), but can also occur as part of a large number of syndromes involving other organ systems (20%). A number of investigations are indicated to try and identify the underlying cause, but even so a precise genetic diagnosis may be difficult. In the absence of a family history, empiric recurrence risk and offspring risk figures are available.
Incidence: Congenital sensorineural deafness affects about 1 in every 1,000 children and in half of these the cause is genetic.
Inheritance : Single gene disorders account for half of all cases. 6% follow an autosomal dominant inheritance pattern and 43.5% an autosomal recessive pattern. X-linked recessive inheritance accounts for 0.5% of cases, whilst 30% of cases can be attributed to environmental factors. In 20% of cases there is no identifiable cause.
Gene: Several hundred deafness genes exist . The commonest cause of non-syndromic prelingual hearing loss in American and European populations is due to a mutation in the autosomal recessive gene, GJB2 gene (connexin 26 or Cx26) on chromosome 13. Mutations in this gene cause about 20% of childhood deafness. The carrier frequency is about 1 in 30.
If you would like to access specialist information on congenital sensorineural deafness please go to:- Genetests - Congenital sensorineural deafness
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