There are three genetic forms of Usher Syndrome known today (1998):

  • Usher Type I, which also includes balance disturbance. Hearing loss is profound and retinitis pigmentosa becomes symptomatic before school age.

  • Usher Type 2 in which hearing loss is moderate to severe and retinitis pigmentosa may become symptomatic first in young adults. There is no balance disturbance in Usher Type 2.

  • Usher Type 3, in which hearing loss may not be present before school age, is progressive and leads to severe hearing loss. Retinitis pigmentosa varies in severity.

The different types of Usher Syndrome are related to different genes. Most Usher Type 1 families have the deviant gene on chromosome 11, Usher Type 2 families on chromosome 1 and Usher Type 3 families on chromosome 3.

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