Usher syndrome is a form of syndromic RP – that is to say retinitis pigmentosa with extra ocular/systemic involvement.  In addition to retinitis pigmentosa, patients with Usher syndrome develop hearing loss, and account for up to 50% of deaf-blindness. There are 3 types of Usher syndrome, each with a different level of severity of both visual and auditory deficits.

Usher type I

Usher type I is the most common and most severe form of the syndrome. Affected patients have profound congenital hearing loss (hearing loss at birth) and as such often do not develop speech, unless early intervention (e.g. cochlear implants) is provided. Retinitis pigmentosa in Usher type I usually becomes apparent in early life, and by adulthood patients may have progressed to tunnel vision with impaired visual acuity. Usher type I is inherited in an autosomal recessive pattern, and currently 6 genes are known to cause this condition.

Usher type II

Like Usher type I, Usher type II causes congenital hearing loss and retinitis pigmentosa. However, in general patients with Usher type II are less severely affected than those with Usher type I. That being said, wide variation in disease severity has been documented for Usher type II; children with the syndrome may still benefit from hearing aids in order to help speech development and visual impairment can still be significant. Usher II is also autosomal recessive with 3 causative genes identified.

Usher Type III

Usher type III is the least common but most mild form of Usher syndrome. Patients with this form of the disease tend to develop progressive hearing loss starting later in childhood (usually after learning to speak). The progressive retinal disease in Usher type III is also more mild and often presents only in adulthood. Usher type III can be caused by mutations in 2 genes and is inherited in an autosomal recessive fashion.

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