Familial Exudative Vitreoretinopathy, EVR1
Patient Information
Characteristics
Background and History
Vitreoretinopathy refers to a condition in the back of the eye in which a primary retinal disease also impacts the vitreous, the jelly-like material that fills much of the eye. It is believed to begin at birth when the retinal vessels are interrupted in development causing the retina to be starved of oxygen. This sets into motion a chain of events that leads to the growth of new abnormal vessels which subsequently bleed causing scarring of the retina and vitreous that may ultimately cause a retinal detachment and blindness. EVR1 is one of several disorders that result from this process.
Clinical Correlations
There is considerable clinical variability in the signs and symptoms, even within families. It usually affects both eyes but can be quite asymmetrical. The condition begins at birth and may progress rapidly to blindness in infants and young children. More frequently, the disease process is arrested at some point and many adults are asymptomatic and the diagnosis is only made during a routine eye examination. Cataracts may develop. The most serious result from the disease process is a retinal detachment which, if untreated, leads to blindness.
Genetics
Inheritance
Familial exudative vitreoretinopathy can be inherited in autosomal dominant, autosomal recessive, and X-linked patterns as a result of mutations in at least 3 and possibly 4 genes.
In EVR1, the pattern of inheritance is vertical, or autosomal dominant, as the disorder is passed directly from parent to child. Only one mutation is required for the disease to become manifest.
Pedigree
Autosomal dominant
Autosomal dominant disorders require only one mutation for the disease to be expressed. Since an affected parent has two chromosomes, only one of which has the mutant gene, parents can expect that half (50%) of their children will receive that one and inherit the disease. It is common for individuals that inherit the mutation, however, to not have evidence of the disease (nonpenetrance).
Autosomal dominant inheritance leads to a vertical pattern of transmission
Diagnosis and Prognosis
The diagnosis can only be made by an ophthalmologist by direct examination of the eye. The prognosis is unpredictable for some patients have minimal or no symptoms while other eyes become blind. Various surgical treatments for cataracts and retinal disease can be beneficial in the restoration of vision.
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