A fifth locus for otosclerosis, OTSC5, maps to chromosome 3q22-24

Otosclerosis is caused by abnormal bone homeostasis of the otic capsule leading to bony fixation of the stapedial footplate in the oval window. Because the transmission of sound waves from outer to inner ear is disturbed by this fixation, the disease is characterised by conductive hearing impairment. In some cases, an additional sensorineural component develops across all frequencies, leading to mixed hearing impairment. The conductive component of the hearing impairment can be restored by stapes replacing microsurgery; however, the sensorineural component cannot surgically be corrected. Otosclerosis has a prevalence of 0.3–0.4% in the Caucasian population. The etiology of the disease is unknown, but epidemiological studies indicate the involvement of genetic as well as environmental factors. However, large families segregating otosclerosis are very rare, whereas there are frequent sporadic cases and smaller families with only a few affected members. Based on these findings, otosclerosis can be considered a genetically complex disease, ..