This is a disorder of the eye primarily affecting the retina that detects the light and color. Individuals with this disorder present severe visual impairment in infancy. Different subtypes of Leber Congenital Amaurosis are identified that is caused by various genetic mutations. These sub-types are also based on the pattern of vision problem and associated eye abnormalities. It is estimated that around 10-18% of all congenital blindness or severe vision problems are caused by Leber Congenital Amaurosis.
Causes
There are around 14 different genetic mutations that are identified to cause this disorder. The common genetic mutations occur in the CEP290, CRB1, GUCY2D and RPE65 genes. All the 14 genes are important for the development and the normal function of the retina. Some of the genes associated with this condition are necessary for the production of light-detecting cells known as photoreceptors and others for the production of phototransduction which processes the light into the electrical signal that is delivered to the brain. Other genes are involved in the normal function of cilia which are essential for the various types of sensory input such as vision. Mostly, the Leber Congenital Amaurosis is inherited in an autosomal recessive pattern meaning both the copies of the genes from the parents have mutations. In some cases, the new genetic mutation can cause this disorder with no history of this condition in the family.
Symptoms
Children with this disorder are born with the absence of functioning rods and cones of the retina. The initial sign is the decrease in visual response at the birth of the infant. The absence of the electrical activity of the retina helps with the diagnosis of this condition. Additional symptoms can include crossed eyes (strabismus), involuntary movement of the eye (nystagmus), clouding of the eye lenses (cataracts), sensitivity to light (photophobia) and the abnormal protrusion of the front (anterior). The affected children may also exhibit mental retardation, developmental delay and hearing loss.
Diagnosis
Leber Congenital Amaurosis is diagnosed by the ophthalmologist based on the symptoms and physical findings during the examination. An electroretinogram may be necessary to evaluate the function of the rods and the cones of the retina. Infants with this condition have the absent or reduced activity of the retina. In around 50% of the cases, the molecular genetic test can detect the genes that are responsible for causing this disorder. It can also help identify the carrier of the disorder among the siblings and the parents.
Treatment
There are no treatments available for most types of Leber Congenital Amaurosis. The treatment is usually symptomatic and supportive. Routine examinations are recommended for individuals with this condition to diagnose the other eye problem. Educational programs can be helpful for the patients with Leber Congenital Amaurosis. Genetic counseling is recommended for the affected individuals and their family.
References
https://rarediseases.org/rare-diseases/leber-congenital-amaurosis/
https://ghr.nlm.nih.gov/condition/leber-congenital-amaurosis#inheritance
https://www.aapos.org/terms/conditions/66
https://rarediseases.info.nih.gov/diseases/634/leber-congenital-amaurosis
