Isolated hearing loss associated with T7511C mutation in mitochondrial DNA.
CONCLUSIONS
The T7511C mutation is considered responsible for maternally inherited, isolated sensorineural hearing loss of cochlear origin. This mutation should be screened for in cases of nonsyndromic, familial sensorineural hearing loss compatible with maternal transmission.


OBJECTIVE
To clarify the audiovestibular phenotype characteristics associated with a T7511C mutation in mitochondrial DNA and determine whether it causes isolated sensorineural hearing loss unaccompanied by other neuromuscular symptoms or signs.


METHODS
A proband and affected members of a Japanese family harboring a T7511C mutation in the mitochondrial tRNA(Ser(UCN)) gene were enrolled. Mutation analysis was done on genomic DNA extracted from blood samples. Auditory pathways involved were investigated in examinations that included pure-tone audiograms, acoustic reflexes, speech discrimination testing, distortion-product otoacoustic emissions, and auditory brainstem responses. The presence of other signs and symptoms, including vestibular ones, was investigated.


RESULTS
We identified a homoplasmic T7511C mutation in the mitochondrial tRNA(Ser(UCN)) gene in this family. No other pathogenic mutations associated with hearing loss or common mitochondrial diseases were found. Hearing loss of cochlear origin mainly developed at mid to high frequencies. Vestibular systems were well preserved. No symptoms or signs characteristic of mitochondrial diseases were present in any family members.
Yamasoba
Tatsuya
T
Department of Otolaryngology and Head and Neck Surgery, University of Tokyo, 7-3-1 Hongo, Bunkyou-ku, Tokyo, Japan. tyamasoba-tky@umin.ac.jp
Tsukuda
Katsunori
K
Suzuki
Mitsuya
M
D000328:Adult; D001301:Audiometry, Pure-Tone; D002150:Caloric Tests; D002648:Child; D016241:Child of Impaired Parents; D003051:Cochlea / Q000503:physiopathology*; D000072259:Connexin 26; D017630:Connexins / Q000235:genetics*; D004252:DNA Mutational Analysis; D004272:DNA, Mitochondrial / Q000235:genetics*; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*; D005260:Female; D015870:Gene Expression / Q000235:genetics*; D006319:Hearing Loss, Sensorineural / Q000175:diagnosis / Q000235:genetics* / Q000503:physiopathology*; D006801:Humans; D017084:Otoacoustic Emissions, Spontaneous / Q000502:physiology; D010375:Pedigree; D010641:Phenotype; D017354:Point Mutation / Q000235:genetics*; D011110:Polymorphism, Genetic / Q000235:genetics; D012343:RNA, Transfer / Q000235:genetics
D017630:Connexins; D004272:DNA, Mitochondrial; D000072259:Connexin 26; D012343:RNA, Transfer