title: Postlingual hearing loss as a mitochondrial 3243A>G mutation phenotype.
abstract: BACKGROUND
  The prevalence of isolated hearing loss (HL) associated with the m.3243A>G mutation is unknown. The aim of this study was to assess the frequency and heteroplasmy level of the m.3243A>G mutation in a large group of Polish patients with postlingual bilateral sensorineural HL of unidentified cause.
  
  
  RESULTS
  A molecular search was undertaken in the archival blood DNA of 1482 unrelated patients with isolated HL that had begun at ages between 5 and 40 years. Maternal relatives of the probands were subsequently investigated and all carriers underwent audiological tests. The m.3243A>G mutation was found in 16 of 1482 probands (an incidence of 1.08%) and 18 family members. Of these 34 individuals, hearing impairment was detected in 29 patients and the mean onset of HL was at 26 years. Some 42% of the identified m.3243A>G carriers did not develop multisystem symptomatology over the following 10 years. Mean heteroplasmy level of m.3243A>G was lowest in blood at a level of 14% and highest in urine at 58%. These values were independent of the manifested clinical severity of the disease.
  
  
  CONCLUSIONS
  A single m.3243A>G carrier can usually be found among each 100 individuals who have postlingual hearing loss of unknown cause. Urine samples are best for detecting the m.3243A>G mutation and diagnosing mitochondrially inherited hearing loss.
authors.affiliation: Institute of Physiology and Pathology of Hearing, Warsaw, Poland.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Iwanicka-Pronicka
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Pollak
authors.forename: Agata
authors.initials: A
authors.lastname: Skórka
authors.forename: Urszula
authors.initials: U
authors.lastname: Lechowicz
authors.forename: Magdalena
authors.initials: M
authors.lastname: Pajdowska
authors.forename: Mariusz
authors.initials: M
authors.lastname: Furmanek
authors.forename: Maciej
authors.initials: M
authors.lastname: Rzeski
authors.forename: Lech
authors.initials: L
authors.lastname: Korniszewski
authors.forename: Henryk
authors.initials: H
authors.lastname: Skarżyński
authors.forename: Rafał
authors.initials: R
authors.lastname: Płoski
mesh_terms: D000225:Adenine / Q000737:chemistry; D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D001921:Brain / Q000473:pathology; D004247:DNA / Q000032:analysis; D004252:DNA Mutational Analysis; D004272:DNA, Mitochondrial / Q000235:genetics; D005260:Female; D006147:Guanine / Q000737:chemistry; D006319:Hearing Loss, Sensorineural / Q000453:epidemiology / Q000235:genetics*; D006579:Heterozygote; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009154:Mutation; D011044:Poland; D012737:Sex Factors
chemical_list: D004272:DNA, Mitochondrial; D006147:Guanine; D004247:DNA; D000225:Adenine