Leber's amaurosis: causes, symptoms, diagnosis, treatment

Leber's congenital amaurosis is the most severe manifestation of retinitis pigmentosa (generalized form), observed from birth; - a very rare and serious disease with systemic manifestations.

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What causes Leber's amaurosis?

The cause of the disease is the lack of differentiation of pigment epithelial cells and photoreceptors.

The disease is more commonly transmitted in an autosomal recessive manner and has recently been linked to two different genes, including a mutation in the rhodopsin gene. Leber's amaurosis is now considered a heterogeneous group of disorders that affect rods and cones.

Symptoms of Leber's amaurosis

Main symptoms: absence of central vision, unrecordable or sharply subnormal ERG, nystagmus. Diagnosis of congenital Leber's amaurosis is very difficult, since the symptoms detected in patients: strabismus, keratoconus, high hyperopia, neurological and neuromuscular disorders, hearing loss, mental retardation, can also be present in other systemic diseases. It manifests itself as blindness at birth or in the first few months of life. In many children, vision improves with brighter lighting.

In this disease, children are either born blind or lose their sight at about 10 years of age. During the first 3-4 months of life, most parents note that their children have no ability to fixate on objects or respond to light, and typical eye symptoms characteristic of children born blind: wandering gaze and nystagmus, which are noted already in the first months of life. In infants, the fundus may look normal, but pathological changes inevitably appear over time. Eye symptoms include various pigment changes in the posterior pole of the eye from hyperpigmented to non-pigmented salt-and-pepper lesions, retinal pigment migration and pigment clusters, atrophy of the pigment epithelium and choroidal capillaries, and, less commonly, multiple, unevenly distributed yellowish-white spots on the periphery and midperiphery of the retina. Pigment deposits in the form of bone bodies on the periphery of the fundus are found in almost all patients with Leber's amaurosis at the age of 8-10 years, but these deposits can be very small, resembling a rash with rubella. The optic disc is usually pale, the retinal vessels are narrowed. Changes in the fundus usually progress, but unlike typical pigment retinitis, functional changes (visual acuity, visual field, ERG) usually remain the same as at the initial examination. Over time, after 15 years, patients with Leber's amaurosis may develop keratoconus.

Diagnosis of Leber's amaurosis

Microscopic examination reveals subretinal inclusions consisting of rejected outer segments of photoreceptors and macrophages in areas corresponding to ophthalmoscopically visible white spots. The outer segments of the rods are absent, a small number of altered cones are preserved, other cellular elements are undifferentiated photoreceptors and embryonic cells of the pigment epithelium.

Differential diagnosis is carried out with dominant optic nerve atrophy, in which the prognosis regarding vision is significantly better, as well as with similar changes in rubella and congenital syphilis.

The main symptom of Leber's congenital amaurosis, on which differential diagnosis is based, is either unrecordable or significantly subnormal ERG, while in optic nerve atrophy, syphilis and rubella ERG is either normal or subnormal. In Leber's congenital amaurosis, various widespread neurological and neurodegenerative disorders, cerebral atrophy, mental retardation, and kidney disease are possible. However, the intellectual development of children with Leber's congenital amaurosis may be normal.

Diagnostic criteria for Leber's amaurosis:

• Pupillary reflexes are sluggish or absent.

• There may be no changes in the fundus, despite low visual acuity.
• The most common symptom is areas of peripheral chorioretinal atrophy and pigment redistribution.
• Other symptoms include papilledema, salt-and-pepper changes, diffuse white spots, macular coloboma, and bull's-eye maculopathy.
• Optic disc pallor and decreased arteriolar caliber appear simultaneously with ophthalmoscopic manifestations.

Other ophthalmologic symptoms:

• Hypermetropia, keratoconus and keratoglobus.
• Cataracts can occur in the 2nd decade of life.
• Nystagmus, wandering eye movements, strabismus.
• A characteristic symptom is oculofingual syndrome, in which frequent rubbing of the eyeballs leads to enophthalmos and resorption of orbital fat tissue.

Electroretinogram is usually not recorded even in the early stages with a normal fundus.

The prognosis is extremely unfavorable. It may be accompanied by mental retardation, deafness, epilepsy, CNS and kidney abnormalities, congenital skeletal malformations, and endocrine dysfunction.

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