Retinitis Pigmentosa 75
Patient Information
Characteristics
Background and History
Retinitis pigmentosa (RP) consists of a large group of disorders resulting from a progressive loss of the rods and cones in the retina. These are the cells that respond to light and send signals to the brain that enable us to see. More than 100 mutant genes have been identified as responsible for these hereditary disorders and there is considerable variation in onset and progression of symptoms. The disease usually is present as an isolated eye disease but syndromal forms also occur in which there is a similar disease of the retina in association with other problems elsewhere in the body.
Clinical Correlations
Symptoms of night blindness usually have their onset in the first decade of life. The field of vision is restricted by loss of the peripheral areas which results in ‘tunnel vision’. Inside the eye the retinal pigment is characteristically clumped in a recognizable pattern known as ‘bone spicule’ pigmentation. The retinal vessels are abnormally narrow which is described in the medical literature as ‘attentuation’. The optic nerve which connects the eye to the brain shows damage as well. Most patients are highly nearsighted.
Genetics
Inheritance
A gene change (mutation) in both members of a specific pair is responsible for this condition. The parents who only carry the change in a single member of the pair are clinically normal but if both carry this change, each of their children are born with a 25% risk of developing this form of retinitis pigmentosa.
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
Only the eyes demonstrate changes as the result of the mutation and patients are otherwise healthy. An eye physician can diagnose this condition based on the symptoms and the characteristic changes in the retina and optic nerve. There is no known treatment and no impact on general health or longevity.
Low vision aids could be beneficial, especially for school age children.
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