The objective of this study was to characterize hearing loss in individuals with deletions of distal chromsome18q and to identify the smallest region of overlap of their deletions, thereby identifying potential causative genes.
The clinical data were collected via a retrospective case study. Molecular data were obtained via high-resolution chromosome microarray analysis.
The study was conducted as a component of the ongoing research protocols at the Chromosome 18 Clinical Research Center at the University of Texas Health Science Center at San Antonio.
Thirty-eight participants with a deletion of the distal portion of the long arm of chromosome 18 were recruited to this study.
The participants underwent an otologic examination as well as a basic audiometry evaluation. Blood samples were obtained, and high-resolution chromosome microarray analysis was performed.
Main Outcomes Measures
Pure tone averages and speech discrimination scores were determined for each participant. The region of hemizygosity for each participant was determined to within 2 Kb each of their breakpoints.
Twenty-four participants (63%) had high-frequency hearing loss, similar to the pattern seen in presbycusis. Comparison of microarray results allowed identification of eight genes, including the candidate gene for dysmyelination (MBP).
Individuals with a deletion of a 2.8 Mb region of 18q23 have a high probability (83%) of high-frequency sensorineural hearing loss.