Phenotype of DFNA11: a nonsyndromic hearing loss caused by a myosin VIIA mutation.

OBJECTIVES/HYPOTHESIS: To characterize the audiovestibular phenotype of DFNA11, an autosomal dominant nonsyndromic hearing impairment caused by a mutation in the myosin VIIA gene (MYO7A), including whether DFNA11-affected subjects have retinal degeneration as is characteristic of Usher syndrome type 1B, caused by different MYO7A mutations.

STUDY

DESIGN

Retrospective study of audiovestibular and ophthalmological data in a Japanese family linked to DFNA11.

METHODS

Otoscopic examination and pure-tone audiometry were performed in all participants in the family. Selected subjects underwent additional examinations including speech discrimination scoring, acoustic reflex measurements, Békésy audiometry, evoked and distortion-product otoacoustic emissions, auditory brainstem responses, and bithermal caloric testing; visual acuity, ocular tonometry, slit-lamp examination, ophthalmoscopy, and electroretinography; and computed tomography of the temporal bone.

RESULTS

Most affected individuals had moderate cochlear hearing loss beginning in the second decade and progressing at all frequencies. Variable degrees of asymptomatic vestibular dysfunction were present. Computed tomography showed normal inner and middle ear structures. No evidence suggested retinitis pigmentosa.

CONCLUSIONS

The phenotype of DFNA11 is postlingual, nonsyndromic sensorineural hearing loss with gradual progression. Showing moderate hearing loss with asymptomatic variable vestibular dysfunction and no retinal degeneration, the DFNA11 phenotype is mildest among phenotypes caused by MYO7A mutations.