Retinitis Pigmentosa
1. What is Retinitis Pigmentosa?
Retinitis Pigmentosa (RP) is a general name for a
group of eye conditions, all of which are known to be hereditary.
In all cases RP affects the light sensitive nerve tissue at the
back of the eye, known as the retina, causing a progressive reduction
in the visual function.
There are three ways in which RP may be inherited:
Autosomal Dominant Inhertitance
Where RP is known to exist in both the male and female members
of a family, there is a 50% risk of a child inheriting RP from the
affected parent.
Autosomal Recessive Inheritance
Where there is no known history of RP in a family. However if two
carriers have a child there would be a 25% risk of the child developing
RP, even when neither parent shows any obvious signs of RP.
X-Linked Inheritance
This is a more complicated form of inheritance in which only the
males may develop the condition. Female members of the family become
carriers and may develop very mild forms of RP. In a typical case,
the sons of a man suffering from X-Linked RP will not develop the
condition, but all of his daughters will become carriers. These
daughters will each then have a 50% risk of producing an affected
son. Similarly they will have a 50% chance of producing a daughter
who is a carrier.
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