Retinal Dystrophy and Obesity
Patient Information
Characteristics
Background and History
This is a rare heritable condition so far reported in one family in which obesity was associated with a progressive retinal degeneration (dystrophy).
Clinical Correlations
Night blindness and a progressive reduction in vision are features. Examination of the retina shows a loss of pigmentation with narrowing of retinal blood vessels. Color vision testing reveals mild but nonspecific alterations in color vision. An ERG (electroretinogram) test shows a generalized malfunction of the rods and cones. Peripheral vision is more severely affected than central vision. Patients may not have symptoms until the second or third decade of life.
Obesity and an elevated body mass index (BMI) seem to be the only systemic findings in this disorder.
Genetics
Inheritance
A gene mutation is responsible for this autosomal recessive condition. Affected individuals must have both copies of the mutation while carriers (such as parents with only one copy) are normal. Such parents can expect that 1 in 4 of their children will inherit both copies and suffer from this condition.
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 is most likely made by an eye doctor based on an eye examination. Little is known of the natural history of this condition but it likely does not impact longevity. Low vision aids may be helpful to achieve reading vision.
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