Retinal Dystrophy With Or Without Extraocular Anomalies
Patient Information
Characteristics
Background and History
There are many types of inherited retinal disease. Most do not have abnormalities outside of the eye but this one is an exception. The retina in the back of the eye contains rods and cones that normally respond to light and transmit the information to the brain which allows us to see but in this condition these progressively deteriorate causing visual problems.
Clinical Correlations
Visual symptoms begin in the first decade or two of life when there is difficulty seeing at night. Abnormality of pigmentation in the retina is also a common finding. Most individuals also have some mild intellectual disability but other abnormalities outside of the eye are highly variable. Nodules or goiter of the thyroid are often present and females may have amenorrhea and other evidence of ovary malfunction. One family had hearing loss and one patient had scarring of the lungs.
Genetics
Inheritance
This condition follows an autosomal recessive pattern of inheritance in which two mutations in a specific gene must be present. One mutation is contributed by each parent. The parents with a single mutation each are clinically normal. However, each of their children have a 25% risk of inheriting 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 disorder is unlikely to be diagnosed at birth since there are no external signs. Some developmental delay and intellectual disability may be evident during childhood but the signs are nonspecific. Visual symptoms later may lead to additional evaluations that point to this condition. Pediatricians, ophthalmologists, obstreticians, and psychologists may collaborate on the diagnosis and care of patients that have this condition.
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