Prevalence of mitochondrial DNA mutations in childhood/congenital onset non-syndromal sensorineural hearing impairment

Genetic factors are the major causes of childhood hearing impairment. Where as autosomal recessive mutations account for the majority of prelingual non syndromic sensorineural hearing impairment (NSSHI), the relative contributi on of mitochondrial DNA (mtDNA) mutations to childhood onset NSSHI has not been established. We screened 202 subjects with congenital/ childhood onset NSSHI, consisting of 110 sporadic cases, 75 sib pairs, and 17 families with affected subject s in more than one generation, in order to determine the prevalence of mtDN A mutations associated with NSSHI. mtDNA mutations were found in three of 10 families (30%) in whom the affect ed members were related through the maternal lineage. One sporadic case (0. 9%) was also found to have a known mtDNA mutation but none was found in the sib pairs. Although the prevalence of mtDNA mutations was low in the group as a whole (2%), we suggest that screening should be considered in cases of childhood hearing impairment when it is progressive and particularly in families wher e transmission is compatible with maternal inheritance.