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Leber congenital amaurosis 9(LCA9)

MedGen UID:
325277
Concept ID:
C1837873
Disease or Syndrome
Synonyms: Amaurosis congenita of Leber, type 9; LCA 9; LCA9; LCA9 Leber Congenital Amaurosis; Leber Congenital Amaurosis; NMNAT1-Related Leber Congenital Amaurosis
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): NMNAT1 (1p36.22)
OMIM®: 608553

Definition

Leber congenital amaurosis (LCA), a severe dystrophy of the retina, typically becomes evident in the first year of life. Visual function is usually poor and often accompanied by nystagmus, sluggish or near-absent pupillary responses, photophobia, high hyperopia, and keratoconus. Visual acuity is rarely better than 20/400. A characteristic finding is Franceschetti's oculo-digital sign, comprising eye poking, pressing, and rubbing. The appearance of the fundus is extremely variable. While the retina may initially appear normal, a pigmentary retinopathy reminiscent of retinitis pigmentosa is frequently observed later in childhood. The electroretinogram (ERG) is characteristically "nondetectable" or severely subnormal. [from GTR]

Additional descriptions

From GeneReviews
Leber congenital amaurosis (LCA), a severe dystrophy of the retina, typically becomes evident in the first year of life. Visual function is usually poor and often accompanied by nystagmus, sluggish or near-absent pupillary responses, photophobia, high hyperopia, and keratoconus. Visual acuity is rarely better than 20/400. A characteristic finding is Franceschetti's oculo-digital sign, comprising eye poking, pressing, and rubbing. The appearance of the fundus is extremely variable. While the retina may initially appear normal, a pigmentary retinopathy reminiscent of retinitis pigmentosa is frequently observed later in childhood. The electroretinogram (ERG) is characteristically "nondetectable" or severely subnormal.  https://www.ncbi.nlm.nih.gov/books/NBK1298
From OMIM
Early-onset neurodegeneration in the human retina can lead to Leber congenital amaurosis (LCA), the most severe human form of inherited photoreceptor-neuron degeneration resulting in congenital blindness, with an incidence of approximately 1 in 80,000 (summary by Koenekoop et al., 2012). NMNAT1 (608700) mutations consistently cause severe and rapidly progressive macular degeneration leading to severe central atrophy with an appearance of congenital macular coloboma in the neonatal period, as well as an unusual early-onset atrophy of the optic nerve (Perrault et al., 2012).  http://www.omim.org/entry/608553
From GHR
Leber congenital amaurosis is an eye disorder that 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 in infancy. The visual impairment tends to be stable, although it may worsen very slowly over time.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. Additionally, the clear front covering of the eye (the cornea) may be cone-shaped and abnormally thin, a condition known as keratoconus.A specific behavior called Franceschetti's oculo-digital sign is characteristic of Leber congenital amaurosis. This sign consists of poking, pressing, and rubbing the eyes with a knuckle or finger. Researchers suspect that this behavior may contribute to deep-set eyes and keratoconus in affected children.In rare cases, delayed development and intellectual disability have been reported in people with the features of Leber congenital amaurosis. However, researchers are uncertain whether these individuals actually have Leber congenital amaurosis or another syndrome with similar signs and symptoms.At least 13 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://ghr.nlm.nih.gov/condition/leber-congenital-amaurosis

Clinical features

Hypermetropia
MedGen UID:
43780
Concept ID:
C0020490
Disease or Syndrome
A refractive error in which rays of light entering the eye parallel to the optic axis are brought to a focus behind the retina, as a result of the eyeball being too short from front to back. It is also called farsightedness because the near point is more distant than it is in emmetropia with an equal amplitude of accommodation. (Dorland, 27th ed)
Nyctalopia
MedGen UID:
10349
Concept ID:
C0028077
Disease or Syndrome
An inability to see clearly in dim light; due to a deficiency of vitamin A or to a retinal disorder.
Nystagmus
MedGen UID:
45166
Concept ID:
C0028738
Disease or Syndrome
Involuntary movements of the eye that are divided into two types, jerk and pendular. Jerk nystagmus has a slow phase in one direction followed by a corrective fast phase in the opposite direction, and is usually caused by central or peripheral vestibular dysfunction. Pendular nystagmus features oscillations that are of equal velocity in both directions and this condition is often associated with visual loss early in life. (Adams et al., Principles of Neurology, 6th ed, p272)
Optic atrophy
MedGen UID:
18180
Concept ID:
C0029124
Disease or Syndrome
A disorder characterized by loss of optic nerve fibers. It may be inherited or acquired. Acquired causes include ischemia, optic nerve neuropathy, glaucoma, trauma, radiation, brain tumors, and multiple sclerosis. It leads to vision disturbances.
Photophobia
MedGen UID:
43220
Concept ID:
C0085636
Sign or Symptom
Abnormal sensitivity to light. This may occur as a manifestation of EYE DISEASES; MIGRAINE; SUBARACHNOID HEMORRHAGE; MENINGITIS; and other disorders. Photophobia may also occur in association with DEPRESSION and other MENTAL DISORDERS.
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.
Coloboma of macula
MedGen UID:
342305
Concept ID:
C1852767
Congenital Abnormality
A congenital defect of the macula distinct from coloboma associated with optic fissure closure defects.
Attenuation of retinal blood vessels
MedGen UID:
480605
Concept ID:
C3278975
Finding
Attenuation of retinal blood vessels
MedGen UID:
480605
Concept ID:
C3278975
Finding
Photophobia
MedGen UID:
43220
Concept ID:
C0085636
Sign or Symptom
Abnormal sensitivity to light. This may occur as a manifestation of EYE DISEASES; MIGRAINE; SUBARACHNOID HEMORRHAGE; MENINGITIS; and other disorders. Photophobia may also occur in association with DEPRESSION and other MENTAL DISORDERS.
Coloboma of macula
MedGen UID:
342305
Concept ID:
C1852767
Congenital Abnormality
A congenital defect of the macula distinct from coloboma associated with optic fissure closure defects.

Recent clinical studies

Clinical prediction guides

Sasaki Y, Margolin Z, Borgo B, Havranek JJ, Milbrandt J
J Biol Chem 2015 Jul 10;290(28):17228-38. Epub 2015 May 27 doi: 10.1074/jbc.M115.637850. PMID: 26018082Free PMC Article

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