Connexin 26 mutation in keratitis-ichthyosis-deafness (KID) syndrome in mother and daughter with combined conductive and sensorineural hearing loss

Background: Keratitis-ichthyosis-deafness (KID) syndrome most commonly results from a mutation in the gap-junctional protein connexin 26 (Cx26) gene, GJB2. Most cases are sporadic and are associated with sensorineural hearing loss. Methods: We encountered a mother and daughter with KID syndrome, and pursued genetic analysis and an extensive hearing loss evaluation. Results: The analysis of genomic DNA of both affected patients revealed the mutation 148G → A in GJB2 (D50N). No mutation was found in an unaffected son. Auditory phenotype analysis showed a combined conductive and sensorineural hearing loss in both affected patients. Conclusions: This is the second vertical transmission of the D50N mutation. These are the first two cases with combined sensorineural and conductive hearing loss without any significant history of middle ear disease. This points to the possibility that the Cx26 D50N mutation can cause conductive hearing loss.