Two large Spanish pedigrees with nonsyndromic sensorineural deafness and the mtDNA mutation at nt 1555 in the 12s rRNA gene: evidence of heteroplasmy

Neurology. 1997 Feb;48(2):453-6. doi: 10.1212/wnl.48.2.453.


We describe two unrelated Spanish families with isolated sensorineural hearing loss. In both pedigrees, the deafness was transmitted maternally, which suggested a mitochondrial, DNA (mtDNA) defect. Within the same pedigree, some relatives showed aminoglycoside-induced deafness, whereas others were not exposed to aminoglycosides before the onset of hearing loss. Molecular genetic analysis in both families showed the A-to-G transition at nt 1555 (A1555G) in the mitochondrial 12S rRNA gene. In one pedigree, the mutation was homoplasmic; in the other, it was heteroplasmic. To assess the frequency of this mutation, we screened 42 patients of various ethnic backgrounds with isolated sensorineural hearing loss; none harbored the A1555G mutation. This is the first report of heteroplasmy in a family with isolated sensorineural deafness associated with the A1555G mutation.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • DNA, Mitochondrial / genetics*
  • Deafness / genetics*
  • Female
  • Hispanic Americans
  • Humans
  • Maternal-Fetal Exchange / genetics
  • Middle Aged
  • Molecular Sequence Data
  • Mutation*
  • Oligonucleotide Probes
  • Pedigree
  • Pregnancy
  • RNA, Ribosomal / genetics*


  • DNA, Mitochondrial
  • Oligonucleotide Probes
  • RNA, Ribosomal
  • RNA, ribosomal, 12S