Retinitis Pigmentosa (pigmentosis) is a progressive degenerative disorder of the photoreceptors and/or epithelium pigment of the retina that can cause a profound loss of vision. Various hereditary patterns have been reported. This disease affects 1 out of 3700 people.
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The typical symptoms include decreased night vision and peripheral vision, usually starting in the first or second decade of life. Marked loss of vision occurs over many years but may develop slowly. The diagnosis is made by a thorough eye examination and a special test called an electroretinogram, or "ERG".
- poor adaption in adjusting from light to dark or dark to light.
- poor night vision
- poor peripheral vision
- poor color detection
- errors in color vision in both red-green and blue-yellow ranges
Retinitis pigmentosa is caused by rod and cone photoreceptor or retinal pigment epithelium mutations or abnormalities in the retina.
Retinitis pigmentosa often runs in families. The disorder can be caused by a number of genetic defects.
Many genes can mutate and result in the characteristic retinitis pigmentosa. One mutation is of the gene controlling rhodopsin, a pigment with a critical role in the vision process, that allows vision to work in low-light conditions. Since this discovery, in 1989, 100 other mutations have been found, that account for variations of retinal deterioration. Most of those mutations are recessively inherited - that is, the mutated gene must come from both parents.
Hundreds of different mutations of rods and cones have been identified, more than 100 of the mutations occurring in the rhodopsin molecule alone. For example:
- Rhodopsin overexpression
- Rhodopsin mutations such as RNA splice involving rhodopsin protein filiments or mutation of a single nucleotide in the genetic code, changing the protein
- Rhodopsin C-terminal mutations, wherein the protein tail mutates
- Rhodopsin molecule is engulfed by other cells
- Non retinal cell mutations.
- Deterioration of cone cells
- Deterioration of rod cells
Retinitis pigmentosa usually affects the eye, but there are several other rare conditions that may be be correlated.
- Usher syndrome wherein hearing is affected. The condition is associated with gene mutation.
- Leber's in which mitochondria, the energy producers of retinal nerve cells, malfunction.
- Bardet-Viedl syndrome is often associated with obesity present at childhood and other problems evident at childhood.
- Senior Loken syndrome and Alport syndrome are severe forms of retinitis pigmentosa associated with kidney problems
- Cohen syndrome, Cockayne syndrome and Jeune syndrome connect retinitis pigmentosa with body structure disorders.
- There are a number of diseases that associate retinitis pigmentosa with a wide variety of conditions involving metabolism of vitamins, proteins, lipids, etc.
- Other conditions associate RP with various neurological conditions.
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