Maternally inherited nonsyndromic hearing loss

In this study we characterized clinically and evaluated molecularly a large family with maternally inherited hearing impairment, Relatives were evalua ted audiologically and clinically, the most likely pattern of inheritance w as deduced, and molecular DNA analysis for the known mitochondrial mutation s associated with hearing impairment was performed, Clinical examination of several relatives showed a normal general state of health, but in 14 of th e members tested variable degrees of sensorineural hearing loss were noted. The pedigree was established and demonstrated a clear pattern of maternal inheritance, with 34 of 38 offspring of deaf mothers being hearing impaired , but none of 22 offspring of deaf fathers having any hearing impairment, S ince by far the most likely explanation of such a maternal inheritance patt ern is a mitochondrial mutation, molecular testing for the three known mito chondrial mutations, A1555G, A7445G, and Cins7472, was performed an 27 of t he relatives, All of the individuals tested had the normal sequence at the sites tested. This family with nonsyndromic sensorineural hearing loss has an inheritance pattern strongly suggestive of a mitochondrial mutation, How ever, molecular testing for the three known mitochondrial mutations associa ted with nonsyndromic hearing impairment was negative, implying that additi onal molecular defects can lead to the same phenotype, The search for this novel molecular defect is underway, (C) 1999 Wiley-Liss, Inc.