The Usher Syndromes

Usher syndrome is the most common cause of "deaf/blindness" in developed countries. Its presenting symptom is hearing loss, which means that the audiologist is often the first to see a child with Usher syndrome. Due to the marked heterogeneity of hearing loss, it is often difficult to confirm a diagnosis of Usher syndrome until the onset of visual symptoms. There are three clinical types (I, II, and III) based on severity and age at onset of hearing, visual, and vestibular symptoms. However, there are at least eight molecular subtypes as defined by the specific gene involved. Molecular diagnostic techniques are available on a limited basis to assist the clinician in early confirmation of the diagnosis and in defining specific Usher syndrome genetic subtypes. Furthermore, advances in the understanding of the molecular genetics of Usher syndrome indicate that most, if not all, of the Usher genes produce proteins that work together in a molecular complex. This not only helps explain why mutations in the different genes all produce similar phenotypes, but it offers hope for therapies that may mitigate the vision and hearing losses of all the Usher syndromes. Effective therapy is the ultimate goal and progress is being made toward that objective along several fronts.