A new nonsyndromic X-linked sensorineural hearing impairment linked to Xp21.2

X-linked deafness is a rare cause of hereditary hearing impairment. We have identified a family with X-linked dominant sensorineural hearing impairment, characterized by incomplete penetrance and variable expressivity in carrier females, that is linked to the Xp21.2, which contains the Duchenne muscular dystrophy (DMD) locus. The auditory impairment in affected males was congenital, bilateral, profound, sensorineural, affecting all frequencies, and without evidence of radiographic abnormality of the temporal bone. Adult carrier females manifested bilateral, mild-to-moderate high-frequency sensorineural hearing impairment of delayed onset during adulthood. Eighteen commercially available, polymorphic markers from the X chromosome, generating a 10-15-cM map, were initially used for identification of a candidate region. DXS997, located within the DMD gene, generated a two-point LOD score of 2.91 at theta = 0, with every carrier mother heterozygous at this locus. Recombination events at DXS992 (located within the DMD locus, 3' to exon 50 of the dystrophin gene) and at DXS1068 (5' to the brain promoter of the dystrophin gene) were observed. No recombination events were noted with the following markers within the DMD locus: 5'DYS II, intron 44, DXS997, and intron 50. There was no clinical evidence of Duchenne or Becker muscular dystrophy in any family member. It is likely that this family represents a new locus on the X chromosome, which when mutated results in nonsyndromic sensorineural hearing loss and is distinct from the heterogeneous group of X-linked hearing losses that have been previously described.