title: Deafness due to A1555G mitochondrial mutation without use of aminoglycoside.
abstract: OBJECTIVE
  The objective was to clarify the characteristics of deafness associated with the A1555G mutation within mitochondrial 12S ribosomal RNA gene in the absence of aminoglycoside exposure.
  
  
  METHODS
  Clinical and genetic studies in family members with the A1555G mitochondrial mutation were performed.
  
  
  METHODS
  The subjects were 123 maternally related members of a large Japanese family with the A1555G mutation. All subjects had no previous history of exposure to aminoglycosides. Hearing disability and handicap, tinnitus, and medical histories were analyzed by interviews in all of the subjects, genetic testing was performed in 41 subjects, and pure-tone audiometry was conducted in 26 subjects with hearing disability and handicap.
  
  
  RESULTS
  The A1555G mutation was detected in a homoplasmic form (meaning that all the mitochondrial DNA carries the mutation) in all 41 subjects who were screened. The risk for developing postlingual hearing loss was likely to be much higher in the present subjects than in the general population. Both the severity and age at onset of the phenotype were similar in affected subjects within the same sibling group. Pure-tone averages were significantly worse in subjects who developed hearing loss before age 10 years than in those who developed hearing loss later.
  
  
  CONCLUSIONS
  The present study demonstrated that the prevalence of deafness in individuals with the A1555G mitochondrial mutation was likely to be high even in the absence of aminoglycoside exposure and clearly showed the association of severe to profound hearing loss with the onset of hearing loss before age 10 years.
authors.affiliation: Department of Otolaryngology, National Tokyo Medical Center, Tokyo, Japan. tmatsuna@ntmc.hosp.go.jp
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Matsunaga
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kumanomido
authors.forename: Masae
authors.initials: M
authors.lastname: Shiroma
authors.forename: Akihiro
authors.initials: A
authors.lastname: Ohtsuka
authors.forename: Kenji
authors.initials: K
authors.lastname: Asamura
authors.forename: Shin-Ichi
authors.initials: S
authors.lastname: Usami
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001299:Audiometry; D002648:Child; D004272:DNA, Mitochondrial / Q000235:genetics*; D003638:Deafness / Q000453:epidemiology / Q000235:genetics* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009154:Mutation; D010375:Pedigree; D010641:Phenotype; D015995:Prevalence
chemical_list: D004272:DNA, Mitochondrial