In affected members of a Chinese family with nonsyndromic sensorineural hearing loss showing maternal inheritance (500008), Xing et al. (2006) identified a homoplasmic 827A-G transition in the MTRNR1 gene in a highly conserved A-site. The severe to profound hearing loss showed an early onset before age 3 years. However, there was incomplete penetrance (43.5%), suggesting that the mutation was not sufficient for development of the disorder and implying the existence of modifying factors.
Xing et al. (2006) identified 827A-G mutation in 3 affected members of a Chinese family with aminoglycoside-induced deafness (580000). Family members who carried the mutation and were not exposed to aminoglycosides did not develop hearing loss.
Chaig et al. (2008) identified a homoplasmic 827A-G mutation in 2 Argentinian sisters with aminoglycoside-induced hearing loss. Four additional maternal family members reportedly had moderate deafness without aminoglycoside exposure, but they were not examined by the authors.
