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Usher syndrome, type 3A(USH3A)

MedGen UID:
339336
Concept ID:
C1568248
Disease or Syndrome
Synonyms: USH3A; Usher Syndrome, Type III; USHER SYNDROME, TYPE IIIA
Modes of inheritance:
Autosomal recessive inheritance
MedGen UID:
141025
Concept ID:
C0441748
Intellectual Product
Sources: HPO, OMIM, Orphanet
A mode of inheritance that is observed for traits related to a gene encoded on one of the autosomes (i.e., the human chromosomes 1-22) in which a trait manifests in homozygotes. In the context of medical genetics, autosomal recessive disorders manifest in homozygotes (with two copies of the mutant allele) or compound heterozygotes (whereby each copy of a gene has a distinct mutant allele).
Autosomal recessive inheritance (HPO, OMIM, Orphanet)
 
Gene (location): CLRN1 (3q25.1)
OMIM®: 276902
Orphanet: ORPHA231183

Definition

Usher syndrome type III is characterized by postlingual, progressive hearing loss, variable vestibular dysfunction, and onset of retinitis pigmentosa symptoms, including nyctalopia, constriction of the visual fields, and loss of central visual acuity, usually by the second decade of life (Karjalainen et al., 1985; Pakarinen et al., 1995). For a discussion of phenotypic heterogeneity of Usher syndrome, see USH1 (276900). Genetic Heterogeneity of Usher syndrome Type III Usher syndrome type IIIB (614504) is caused by mutation in the HARS gene (142810) on chromosome 5q31.3. [from OMIM]

Additional description

From GHR
Usher syndrome is a condition characterized by partial or total hearing loss and vision loss that worsens over time. The hearing loss is classified as sensorineural, which means that it is caused by abnormalities of the inner ear. The loss of vision is caused by an eye disease called retinitis pigmentosa (RP), which affects the layer of light-sensitive tissue at the back of the eye (the retina). Vision loss occurs as the light-sensing cells of the retina gradually deteriorate. Night vision loss begins first, followed by blind spots that develop in the side (peripheral) vision. Over time, these blind spots enlarge and merge to produce tunnel vision. In some cases, vision is further impaired by clouding of the lens of the eye (cataracts). However, many people with retinitis pigmentosa retain some central vision throughout their lives.Researchers have identified three major types of Usher syndrome, designated as types I, II, and III. These types are distinguished by their severity and the age when signs and symptoms appear. The types are further divided into subtypes based on their genetic cause.Most individuals with Usher syndrome type I are born with severe to profound hearing loss. Progressive vision loss caused by retinitis pigmentosa becomes apparent in childhood. This type of Usher syndrome also causes abnormalities of the vestibular system, which is the part of the inner ear that helps maintain the body's balance and orientation in space. As a result of the vestibular abnormalities, children with the condition have trouble with balance. They begin sitting independently and walking later than usual, and they may have difficulty riding a bicycle and playing certain sports.Usher syndrome type II is characterized by hearing loss from birth and progressive vision loss that begins in adolescence or adulthood. The hearing loss associated with this form of Usher syndrome ranges from mild to severe and mainly affects the ability to hear high-frequency sounds. For example, it is difficult for affected individuals to hear high, soft speech sounds, such as those of the letters d and t. The degree of hearing loss varies within and among families with this condition, and it may become more severe over time. Unlike the other forms of Usher syndrome, type II is not associated with vestibular abnormalities that cause difficulties with balance.People with Usher syndrome type III experience hearing loss and vision loss beginning somewhat later in life. Unlike the other forms of Usher syndrome, type III is usually associated with normal hearing at birth. Hearing loss typically begins during late childhood or adolescence, after the development of speech, and becomes more severe over time. By middle age, most affected individuals have profound hearing loss. Vision loss caused by retinitis pigmentosa also develops in late childhood or adolescence. Some people with Usher syndrome type III have vestibular abnormalities that cause problems with balance.  https://ghr.nlm.nih.gov/condition/usher-syndrome

Clinical features

Sensorineural hearing loss
MedGen UID:
9164
Concept ID:
C0018784
Disease or Syndrome
Hearing loss resulting from damage to the COCHLEA and the sensorineural elements which lie internally beyond the oval and round windows. These elements include the AUDITORY NERVE and its connections in the BRAINSTEM.
Vestibular dysfunction
MedGen UID:
334848
Concept ID:
C1843865
Finding
An abnormality of the functioning of the vestibular apparatus.

Term Hierarchy

CClinical test,  RResearch test,  OOMIM,  GGeneReviews,  VClinVar  
Follow this link to review classifications for Usher syndrome, type 3A in Orphanet.

Professional guidelines

PubMed

Bolz HJ, Roux AF
Eur J Hum Genet 2011 Aug;19(8) Epub 2011 Mar 9 doi: 10.1038/ejhg.2011.15. PMID: 21697857Free PMC Article

Recent clinical studies

Etiology

Malm E, Ponjavic V, Möller C, Kimberling WJ, Stone ES, Andréasson S
Eur J Ophthalmol 2011 Jan-Feb;21(1):30-8. PMID: 20544672

Prognosis

Malm E, Ponjavic V, Möller C, Kimberling WJ, Stone ES, Andréasson S
Eur J Ophthalmol 2011 Jan-Feb;21(1):30-8. PMID: 20544672

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