Macular Dystrophy, Fenestrated Type
Patient Information
Characteristics
Background and History
There are a large number of hereditary disorders of the retina (the light sensing tissue lining the inside of the eye). They may involve the entire retina but sometimes only specific areas. The central retina consists of an area called the macula in which the light sensing rods and cones are most highly concentrated. Hence, diseases of the macula usually cause the most disruption of vision but the disorder described here is an exception. Clinically apparent and physiologic changes in the retina can be documented but vision remains good throughout life. It has been reported in only two families.
Clinical Correlations
The earliest changes in the retina have been reported in a 4 year old child but older family members have more alterations in the retinal appearance. Thus this is a progressive disorder but symptoms of distorted vision do not seem to occur in until late midlife. Vision as measured on the usual eye charts is apparently normal throughout life. The normal pigmentation of the retina is disturbed and progressively so as well. It is possible to document mild abnormalities in function of the rods and cones with color vision tests and an electroretinogram (ERG).
Individuals with this disorder are otherwise healthy.
Genetics
Inheritance
The pattern of disease transmission is consistent with autosomal dominant inheritance in the two reported families. However, no mutation has been found. A parent with this condition can expect that half of his or her children will inherit the same disorder.
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
An ophthalmologist can make the diagnosis based on an eye examination and electrophysiologic studies. The disorder, while evidently progressive based on the appearance of the retina, does not cause reduced vision but may cause mild distortion of vision in older individuals. No treatment is available.
Longevity is normal.
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