Non-syndromic hearing impairment in a multi-ethnic population of Northeastern Brazil

Int J Pediatr Otorhinolaryngol. 2013 Jul;77(7):1077-82. doi: 10.1016/j.ijporl.2013.04.001. Epub 2013 May 15.

Abstract

Objective: There are many hearing impaired individuals in Monte Santo, a rural municipality in the state of Bahia, Brazil, including multiple familial cases strongly suggestive of a genetic aetiology.

Methods: The present study investigated 81 subjects with hearing impairment (HI) recruited from 36 families. Mutations often associated with HI, i.e. the DFNB1 mutations c.35delG in GJB2, deletions del(GJB6-D13S1830) and del(GJB6-D13S1854), and A1555G in the mitochondrial gene MTRNR1 were initially analyzed, with additional mutations in GJB2 identified by sequencing the coding region of the gene.

Results: Seven different mutations were present in GJB2 with mutations c.35delG and p.Arg75Gln, which are known to be pathogenic, identified in 37.0% of the subjects. Individuals homozygous for the c.35delG mutation were diagnosed in eight families, corresponding to 24.7% of unrelated individuals with nonsyndromic hearing impairment (NSHI), and an additional heterozygote for this mutation was present in a single family. Ten individuals (12.4%) in another family were heterozygous for the mutation p.Arg75Gln.

Conclusions: Significant heterogeneity was observed in the alleles and patterns of NSHI inheritance among the subjects studied, probably due to the extensive inter-ethnic admixture that characterizes the peoples of Brazil, together with a high prevalence of community endogamy and consanguineous marriage.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Brazil / epidemiology
  • Child
  • Child, Preschool
  • Connexin 26
  • Connexin 30
  • Connexins / genetics*
  • Consanguinity
  • Ethnicity / genetics*
  • Female
  • Hearing Loss / ethnology*
  • Hearing Loss / genetics*
  • Humans
  • Male
  • Middle Aged
  • Mutation*
  • Orphan Nuclear Receptors / genetics
  • Polymerase Chain Reaction
  • Polymorphism, Restriction Fragment Length
  • Rural Population / statistics & numerical data*
  • Young Adult

Substances

  • Connexin 30
  • Connexins
  • GJB2 protein, human
  • GJB6 protein, human
  • NR2E3 protein, human
  • Orphan Nuclear Receptors
  • Connexin 26