[Genotype--phenotype correlation limits in sensorineural hearing loss: case report of a three-year-old child with a bilateral cochleovestibular impairment and a molecular variant of the COCH gene]. / Les limites des relations phénotypes--génotypes dans les surdités neurosensorielles: a propos d'un enfant de 3 ans associant dysfonction cochléovestibulaire bilatérale et variant moléculaire du gène COCH.

ABSTRACT

Mutations of the COCH gene inherited in an autosomal dominant mode are responsible for late-onset cochleovestibular impairment on both sides. Our objective is to report the youngest patient (3 years) associating a molecular variant of the COCH gene and a cochleovestibular impairment on both sides. The clinical sequence has started with a vestibular dysfunction in a two-year-old child recurrent rotatory dizziness during 12 months. At the age of 3, a sensorineural hearing loss on both sides has occured associated with spontaneous variation during 6 months. The lack of mutation of the connexin 26, connexin 30 and pendrin genes has reorientated the genetic investigation. A molecular variant of the COCH gene was found in the vWFA2 domain. It was an in-frame deletion predicting the synthesis of an abnormal protein in which 21 aminoacid were missing. Others family members with mutation were asymptomatics. In this isolated case report, the study was in favor of a non pathogenic molecular variant of the COCH gene. For all that, mutations of the COCH gene could be searched in progressive cochleovestibular dysfunctions on both sides in children, even without family affect.