Usher Syndrome

Usher syndrome, an autosomal recessive genetic disorder, is the most common cause of deaf-blindness, estimated to account for more than 50% of cases of dual sensory impairment, 18% of cases of retinitis pigmentosa, and approximately 3% to 6% of cases of congenital deafness. The frequency of Usher syndrome in the United States is approximately 4.4/100,000.

The major symptoms of Usher syndrome include visual and hearing loss, as well as vestibular dysfunction. There are three discrete clinical categories of Usher syndrome: Type I, Type II, and Type III. The three categories are distinguished primarily by severity and age of onset of the various symptoms. Type I Usher syndrome is characterized by congenital severe to profound hearing impairment, progressive retinal degeneration beginning in childhood, and vestibular dysfunction. Type II Usher syndrome is characterized by moderate to severe hearing impairment, typical vestibular functioning, and a later onset of retinal degeneration. Type III Usher syndrome is the rarest form, and is characterized by progressive hearing impairment with variable retinal and vestibular symptoms.

The specific genes involved in the expression of the various types of Usher syndrome, as well as means of prevention and treatment, are currently under investigation. It is recommended that all children exhibiting hearing impairment be screened for Usher syndrome.

References

Astuto, L.M., Bork, J.M., Weston, M.D., Askew, J.W., Fields, R.R., Orten, et al. (2002). CDH23 mutation and phenotype heterogeneity: A profile of 107 diverse families with Usher syndrome and nonsyndromic deafness. American Journal of Human Genetics, 71, 262-275.

Usher Syndrome. Retrieved on February 7, 2006 from http://www.nidcd.nih.gov/health/hearing/usher.asp