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Usher syndrome type 3B(USH3B)

MedGen UID:
482696
Concept ID:
C3281066
Disease or Syndrome
Synonym: USHER SYNDROME, TYPE IIIB
 
Gene (location): HARS1 (5q31.3)
 
Monarch Initiative: MONDO:0013788
OMIM®: 614504

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., 1983; Pakarinen et al., 1995). For a discussion of genetic heterogeneity of type III Usher syndrome, see USH3A (276902). [from OMIM]

Additional description

From MedlinePlus Genetics
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 develop vestibular abnormalities that cause problems with balance.

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.

Researchers have identified three major types of Usher syndrome, designated as types I, II, and III. These types are distinguished by the severity of hearing loss, the presence or absence of balance problems, and the age at which 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. Worsening 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 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 break down. Loss of night vision 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.  https://medlineplus.gov/genetics/condition/usher-syndrome

Clinical features

From HPO
Hearing impairment
MedGen UID:
235586
Concept ID:
C1384666
Disease or Syndrome
A decreased magnitude of the sensory perception of sound.
Photophobia
MedGen UID:
43220
Concept ID:
C0085636
Sign or Symptom
Excessive sensitivity to light with the sensation of discomfort or pain in the eyes due to exposure to bright light.
Hyperactive patellar reflex
MedGen UID:
66003
Concept ID:
C0240116
Finding
Truncal ataxia
MedGen UID:
96535
Concept ID:
C0427190
Sign or Symptom
Truncal ataxia is a sign of ataxia characterized by instability of the trunk. It usually occurs during sitting.
Delayed gross motor development
MedGen UID:
332508
Concept ID:
C1837658
Finding
A type of motor delay characterized by a delay in acquiring the ability to control the large muscles of the body for walking, running, sitting, and crawling.
Horizontal nystagmus
MedGen UID:
124399
Concept ID:
C0271385
Disease or Syndrome
Nystagmus consisting of horizontal to-and-fro eye movements.
Optic disc pallor
MedGen UID:
108218
Concept ID:
C0554970
Finding
A pale yellow discoloration of the optic disk (the area of the optic nerve head in the retina). The optic disc normally has a pinkish hue with a central yellowish depression.
Bull eye maculopathy
MedGen UID:
321812
Concept ID:
C1828210
Finding
Progressive maculopathy characterized by concentric regions of hyper- and hypo-pigmentation.
Attenuation of retinal blood vessels
MedGen UID:
480605
Concept ID:
C3278975
Finding
Visual impairment
MedGen UID:
777085
Concept ID:
C3665347
Finding
Visual impairment (or vision impairment) is vision loss (of a person) to such a degree as to qualify as an additional support need through a significant limitation of visual capability resulting from either disease, trauma, or congenital or degenerative conditions that cannot be corrected by conventional means, such as refractive correction, medication, or surgery.

Term Hierarchy

CClinical test,  RResearch test,  OOMIM,  GGeneReviews,  VClinVar  

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