Usher Syndrome Type II

Excerpt

Clinical characteristics: Usher syndrome type II (USH2) is characterized by the following:

1. Congenital, bilateral sensorineural hearing loss that is mild to moderate in the low frequencies and severe to profound in the higher frequencies

2. Intact or variable vestibular responses

3. Retinitis pigmentosa (RP); progressive, bilateral, symmetric retinal degeneration that begins with night blindness and constricted visual fields (tunnel vision) and eventually includes decreased central visual acuity; the rate and degree of vision loss vary within and among families.

Diagnosis/testing: The diagnosis of USH2 is established in a proband using electrophysiologic and subjective tests of hearing and retinal function. Identification of biallelic pathogenic variants in one of three genes – ADGRV1, USH2A, or WHRN – establishes the diagnosis if clinical features are inconclusive.

Management: Treatment of manifestations: Early fitting of hearing aids and speech training. Children with incomplete speech and sentence rehabilitation with hearing aids and older individuals with severe-to-profound hearing loss should be considered for cochlear implantation. Standard treatments for retinitis pigmentosa; vestibular rehabilitation.

Surveillance: Annual audiometry and tympanometry with hearing aids or cochlear implant to assure adequate auditory stimulation. Annual ophthalmologic evaluation from age 20 years to detect potentially treatable complications such as cataracts, refractive errors, and cystoid macular edema. Annual fundus photography, visual acuity, visual field, electroretinography, optical coherence tomography, and fundus autofluorescence from age ten years.

Agents/circumstances to avoid: Tunnel vision and night blindness can increase the likelihood of accidental injury. Competition in sports requiring a full range of vision may be difficult and possibly dangerous. Progressive loss of peripheral vision impairs the ability to safely drive a car.

Evaluation of relatives at risk: The hearing of at-risk sibs should be assessed as soon after birth as possible to allow early diagnosis and treatment of hearing loss.

Genetic counseling: USH2 is inherited in an autosomal recessive manner. Each subsequent pregnancy of a couple who have had a child with Usher syndrome type II has a 25% chance of resulting in an affected child, a 50% chance of resulting in an unaffected child who is a carrier, and a 25% chance of resulting in an unaffected child who is not a carrier. Prenatal testing and preimplantation genetic testing are possible for pregnancies at increased risk if the pathogenic variants have been identified in the family.