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Leber congenital amaurosis 2(LCA2)

MedGen UID:
348473
Concept ID:
C1859844
Disease or Syndrome
Synonyms: AMAUROSIS CONGENITA OF LEBER II; Amaurosis congenita of Leber, type 2; LCA2; RPE65-Related Leber Congenital Amaurosis
 
Gene (location): RPE65 (1p31.3)
 
Monarch Initiative: MONDO:0008765
OMIM®: 204100

Definition

RPE65-related Leber congenital amaurosis / early-onset severe retinal dystrophy (RPE65-LCA/EOSRD) is a severe inherited retinal degeneration (IRD) with a typical presentation between birth and age five years. While central vision varies, the hallmark of this disorder is the presence of severe visual impairment with a deceptively preserved retinal structure. Vision is relatively stable in the first decade of life, but begins to decline in adolescence. Most affected individuals are legally blind (visual acuity 20/200 and/or visual fields extending <20 degrees from fixation) by age 20 years. After age 20 years, visual acuity declines further and by the fourth decade all affected individuals are legally blind and many have complete loss of vision (i.e., no light perception). Milder disease phenotypes have been described in individuals with hypomorphic alleles. [from GeneReviews]

Additional descriptions

From OMIM
Leber congenital amaurosis comprises a group of early-onset childhood retinal dystrophies characterized by vision loss, nystagmus, and severe retinal dysfunction. Patients usually present at birth with profound vision loss and pendular nystagmus. Electroretinogram (ERG) responses are usually nonrecordable. Other clinical findings may include high hypermetropia, photodysphoria, oculodigital sign, keratoconus, cataracts, and a variable appearance to the fundus (summary by Chung and Traboulsi, 2009). For a general description and a discussion of genetic heterogeneity of LCA, see 204000.  http://www.omim.org/entry/204100
From MedlinePlus Genetics
In very rare cases, delayed development and intellectual disability have been reported in people with the features of Leber congenital amaurosis. Because of the visual loss, affected children may become isolated. Providing children with opportunities to play, hear, touch, understand and other early educational interventions may prevent developmental delays in children with Leber congenital amaurosis.

A specific behavior called Franceschetti's oculo-digital sign is characteristic of Leber congenital amaurosis. This sign consists of affected individuals poking, pressing, and rubbing their eyes with a knuckle or finger. Poking their eyes often results in the sensation of flashes of light called phosphenes. Researchers suspect that this behavior may contribute to deep-set eyes in affected children.

Leber congenital amaurosis is also associated with other vision problems, including an increased sensitivity to light (photophobia), involuntary movements of the eyes (nystagmus), and extreme farsightedness (hyperopia). The pupils, which usually expand and contract in response to the amount of light entering the eye, do not react normally to light. Instead, they expand and contract more slowly than normal, or they may not respond to light at all.

Leber congenital amaurosis, also known as LCA, is an eye disorder that is present from birth (congenital). This condition primarily affects the retina, which is the specialized tissue at the back of the eye that detects light and color. People with this disorder typically have severe visual impairment beginning at birth or shortly afterward. The visual impairment tends to be severe and may worsen over time.

At least 20 genetic types of Leber congenital amaurosis have been described. The types are distinguished by their genetic cause, patterns of vision loss, and related eye abnormalities.  https://medlineplus.gov/genetics/condition/leber-congenital-amaurosis

Clinical features

From HPO
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.
Eye poking
MedGen UID:
115926
Concept ID:
C0233593
Mental or Behavioral Dysfunction
Repetitive pressing, poking, and/or rubbing in the eyes.
Cerebellar vermis hypoplasia
MedGen UID:
333548
Concept ID:
C1840379
Finding
Underdevelopment of the vermis of cerebellum.
Intellectual disability
MedGen UID:
811461
Concept ID:
C3714756
Mental or Behavioral Dysfunction
Intellectual disability, previously referred to as mental retardation, is characterized by subnormal intellectual functioning that occurs during the developmental period. It is defined by an IQ score below 70.
Keratoconus
MedGen UID:
44015
Concept ID:
C0022578
Disease or Syndrome
A cone-shaped deformity of the cornea characterized by the presence of corneal distortion secondary to thinning of the apex.
Night blindness
MedGen UID:
10349
Concept ID:
C0028077
Disease or Syndrome
Inability to see well at night or in poor light.
Nystagmus
MedGen UID:
45166
Concept ID:
C0028738
Disease or Syndrome
Rhythmic, involuntary oscillations of one or both eyes related to abnormality in fixation, conjugate gaze, or vestibular mechanisms.
Cataract
MedGen UID:
39462
Concept ID:
C0086543
Disease or Syndrome
A cataract is an opacity or clouding that develops in the crystalline lens of the eye or in its capsule.
Reduced visual acuity
MedGen UID:
65889
Concept ID:
C0234632
Finding
Diminished clarity of vision.
Absent foveal reflex
MedGen UID:
602333
Concept ID:
C0423420
Finding
Lack of the foveal reflex, which normally occurs as a result of the reflection of light from the ophthalmoscope in the foveal pit upon examination. The foveal reflex is a bright pinpoint of light that is observed to move sideways or up and down in response to movement of the opthalmoscope.
Blindness
MedGen UID:
99138
Concept ID:
C0456909
Disease or Syndrome
Blindness is the condition of lacking visual perception defined as a profound reduction in visual perception. On the 6m visual acuity scale, blindness is defined as less than 3/60. On the 20ft visual acuity scale, blindness is defined as less than 20/400. On the decimal visual acuity scale, blindness is defined as less than 0.05. Blindness is typically characterized by a visual field of no greater than 10 degrees in radius around central fixation.
Optic disc pallor
MedGen UID:
108218
Concept ID:
C0554970
Finding
A pale yellow discoloration of the optic disc (the area of the optic nerve head in the retina). The optic disc normally has a pinkish hue with a central yellowish depression.
Fundus atrophy
MedGen UID:
382226
Concept ID:
C2673929
Finding
Attenuation of retinal blood vessels
MedGen UID:
480605
Concept ID:
C3278975
Finding
Undetectable light- and dark-adapted electroretinogram
MedGen UID:
867212
Concept ID:
C4021570
Finding
Absence of the combined rod-and-cone response on electroretinogram.
Pigmentary retinopathy
MedGen UID:
1643295
Concept ID:
C4551715
Disease or Syndrome
An abnormality of the retina characterized by pigment deposition. It is typically associated with migration and proliferation of macrophages or retinal pigment epithelial cells into the retina; melanin from these cells causes the pigmentary changes. Pigmentary retinopathy is a common final pathway of many retinal conditions and is often associated with visual loss.

Recent clinical studies

Therapy

Ferraz Sallum JM, Godoy J, Kondo A, Kutner JM, Vasconcelos H, Maia A
Ophthalmic Genet 2022 Aug;43(4):550-554. Epub 2022 Apr 13 doi: 10.1080/13816810.2022.2053995. PMID: 35416119
Gruntman AM, Flotte TR
FASEB J 2018 Apr;32(4):1733-1740. doi: 10.1096/fj.201700982R. PMID: 31282760

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