title: Audiologic and genetic features of the A3243G mtDNA mutation.
abstract: BACKGROUND
  Mitochondrial mutations have been shown to be responsible for syndromic and nonsyndromic hearing impairment.
  
  
  OBJECTIVE
  To assess the genotypic-phenotypic correlation of mitochondrial DNA mutations in three generations of a single family.
  
  
  METHODS
  A single family with maternally inherited diabetes and hearing loss was recruited. Genomic DNA was subject to polymerase chain reaction-restriction fragment length polymorphism analysis (ApaI) for A3243G mutation detection and confirmation with direct DNA sequencing. The degree of heteroplasmy for the A3243G mutation in blood DNA samples was quantified. In addition, we reviewed audiological data of A3243G-associated hearing loss cases from the literature to provide details of audiologic features.
  
  
  RESULTS
  Six of 11 family members were recruited. All affected members harbored the A3243G mutation. Four of six members had diabetes. Five of five affected members demonstrated hearing loss ranging from mild to severe. The degree of heteroplasmy ranged from 5.51% to 27.74%.
  
  
  CONCLUSIONS
  Patients with a greater percentage of heteroplasmy have a trend toward more severe phenotypic presentations. Hearing loss is bilateral, sensorineural, and symmetric. The main audiogram shapes found were sloping. Additional studies are necessary to clarify the relationship between degree of heteroplasmy and phenotypic presentation.
authors.affiliation: Department of Otolaryngology, University of Miami Ear Institute, Miami, Florida 33136, USA.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Vivero
authors.forename: Xiaomei
authors.initials: X
authors.lastname: Ouyang
authors.forename: Yeunjung Grant
authors.initials: YG
authors.lastname: Kim
authors.forename: Wendy
authors.initials: W
authors.lastname: Liu
authors.forename: Lilin
authors.initials: L
authors.lastname: Du
authors.forename: Denise
authors.initials: D
authors.lastname: Yan
authors.forename: Xue Zhong
authors.initials: XZ
authors.lastname: Liu
mesh_terms: D000293:Adolescent; D000328:Adult; D001299:Audiometry; D004272:DNA, Mitochondrial / Q000235:genetics*; D005260:Female; D005838:Genotype; D034381:Hearing Loss / Q000235:genetics* / Q000473:pathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008928:Mitochondria / Q000235:genetics; D009154:Mutation; D010375:Pedigree; D010641:Phenotype; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012356:RNA, Transfer, Leu / Q000235:genetics*; D055815:Young Adult
chemical_list: D004272:DNA, Mitochondrial; D012356:RNA, Transfer, Leu