title: [Frequency of the Connexin26/35delG mutation and its characteristic phenotype in patients with hearing impairment and controls in Northeastern Hungary].
abstract: BACKGROUND
  Hereditary hearing impairment is a heterogeneous disorder showing different pattern of inheritance and involving a multitude of different genes. Mutations in the GJB2 gene, especially the 35delG mutation, have been established as a major cause of inherited and sporadic non-syndromic deafness in different populations. Mutations in GJB2 gene, encoding gap junction protein (Connexin 26), may be responsible for up to 50% of cases of autosomal recessive non-syndromic hearing impairment and in 15-30% of sporadic cases.
  
  
  METHODS
  The authors analyzed 15 north east Hungarian families and 30 sporadic cases with nonsyndromic hearing impairment for the 35delG mutation.
  
  
  METHODS
  DNA were tested for the common 35delG mutation by a polymerase chain reaction based restriction enzyme assay (BsiYl).
  
  
  RESULTS
  Fifty two patients showing a homozygous 35delG mutation were audiological examined. Ordinarily these patients showed a prelingual, sensorineural, bilateral, symmetric hearing loss without progression. The audiograms were characterized by sloping or flat patterns. The carrier frequency of the 35delG mutation among control group was 5.1%.
  
  
  CONCLUSIONS
  The phenotypic manifestation varied in 30% of all analyzed patients, making genetic counseling extremely difficult. Due to this knowledge mutation analysis of GJB2 cannot distinctly predict the degree of hearing impairment.
authors.affiliation: Debreceni Egyetem Orvos- és Egészségtudományi Centrum, Altalános Orvostudományi Kar Fül-orr-gégeklinika, Debrecen.
authors.forename: Tímea
authors.initials: T
authors.lastname: Tóth
authors.forename: Susan
authors.initials: S
authors.lastname: Kupka
authors.forename: Nicolaus
authors.initials: N
authors.lastname: Blin
authors.forename: Markus
authors.initials: M
authors.lastname: Pfister
authors.forename: István
authors.initials: I
authors.lastname: Sziklai
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D000072259:Connexin 26; D017630:Connexins / Q000235:genetics*; D004252:DNA Mutational Analysis; D004200:Diseases in Twins / Q000235:genetics; D005260:Female; D006319:Hearing Loss, Sensorineural / Q000453:epidemiology / Q000235:genetics*; D006579:Heterozygote; D006801:Humans; D006814:Hungary / Q000453:epidemiology; D015994:Incidence; D008297:Male; D009154:Mutation; D010641:Phenotype; D011237:Predictive Value of Tests; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012720:Severity of Illness Index; D018433:Twin Studies as Topic
chemical_list: D017630:Connexins; C000607042:GJB2 protein, human; D000072259:Connexin 26