Cataracts, Congenital, with Intellectual Disability
Patient Information
Characteristics
Background and History
A cataract is an opacification of the lens in the eye. This is one of numerous inherited congenital cataract conditions but specifically associated with learning and movement problems.
Clinical Correlations
A consanguineous Tunisian family with three affected children has been reported with this disorder. The opacification is of a specific type in which the opacification occurs in the posterior portion of both lenses. It is presumably present at birth and vision is good following surgical removal of the lenses.
Developmental milestones are delayed. Children do not walk until about 2 years of age and speech begins at about 5 years. They may have some learning difficulties as well. The parents are normal.
Genetics
Inheritance
This condition follows an autosomal recessive inheritance pattern in which both copies of a gene are mutated. The parents are carriers, i.e., they carry a single copy of a gene mutation and do not have cataracts but each of their children have a 25% chance of inheriting the mutation from each of their parents and therefore to have this disorder.
Pedigree
Autosomal recessive
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
Diagnosis and Prognosis
The diagnosis can be made by an ophthalmologist, probably at birth. The developmental delay may not be evident until several years of age and might be detected by a pediatrician or a neurologist.
The cataracts can be surgically removed with restoration of eyesight. Special education might enable better adaptation and learning. There is no evidence of an impact on longevity or of other physical disabilities. Studies of the brain have been normal.
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