[Frequency of the Connexin26/35delG mutation and its characteristic phenotype in patients with hearing impairment and controls in Northeastern Hungary].

INTRODUCTION

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.

STUDY DESIGN

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%.

CONCLUSION

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.