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Retinitis pigmentosa (RP) is an inherited retinal dystrophy leading to progressive loss of the photoreceptors and retinal pigment epithelium and resulting in blindness usually after several decades.
ORPHA:791Classification level: Disorder
- Synonym(s): -
- Prevalence: 1-5 / 10 000
- Inheritance: Autosomal dominant or Autosomal recessive or X-linked recessive or Mitochondrial inheritance
- Age of onset: Childhood, Adolescent, Adult
- ICD-10: H35.5
- OMIM: 180100 180104 180105 180210 268000 268025 268060 300029 300155 300424 300605 312600 312612 400004 600059 600105 600132 600138 600852 601414 601718 602594 602772 604232 604393 606068 607921 608133 608380 609913 609923 610282 610359 610599 611131 612095 612165 612572 612712 612943 613194 613341 613428 613464 613575 613581 613582 613617 613660 613731 613750 613756 613758 613767 613769 613794 613801 613809 613810 613827 613861 613862 613983 614180 614181 614494 614500 615233 615434 615565 615725 615780 615922 616188 616394 616469 616544 616562 617023 617123 617304 617433 617460 617781 618173 618195 618220 618345 618613 618697 618826
- UMLS: C0035334
- MeSH: D012174
- GARD: 5694
- MedDRA: 10038914
Prevalence of RP is reported to be 1/3,000 to 1/5,000. No ethnic specificities have been reported although founder effects are possible.
Retinitis pigmentosa is slowly progressive but relentless. There is however broad variability in age of onset, rate of progression and secondary clinical manifestations. Affected individuals generally first develop night blindness (nyctalopia) due to loss of rod function, often in adolescence or earlier. They then develop peripheral visual field impairment, and over time loss of central vision, usually at late stages, often around midlife. Central visual acuity loss may occur at any age as a result of cystoid macular edema or photoreceptor loss. Posterior subcapsular cataracts are common and severity is age dependent. Reduced color vision may also be found. Fundus examination reveals bone spicule pigment deposits, attenuated retinal vessels, retinal atrophy and waxy optic nerve pallor. Severity is partly correlated with the pattern of inheritance with X-linked cases having the most severe course, autosomal recessive and single occurrence cases having intermediate severity, and autosomal dominant the most favorable course.
More than 3,000 mutations in over 57 different genes or loci are currently known to cause non-syndromic RP.
The diagnosis of RP is based on peripheral visual field loss, pigment deposits in fundus, loss of photoreceptors at the optical coherence tomography (OCT) scan of the retina and decreased or abolished responses as measured by electroretinography (ERG). Molecular genetic testing using single-gene testing, an RP multi-gene panel or exome sequencing allows for genetic subtype classification.
Besides non syndromic forms, there are syndromic forms of RP of which the most frequent are Usher syndrome (RP and deafness) and BardetBiedl syndrome (RP and metabolic impairment). RP is to be distinguished from macular dystrophies (peripheral visual field is normal) and Leber congenital amaurosis (congenital retinal dystrophy) (see these terms).
Prenatal diagnosis for at-risk pregnancies is possible by DNA analysis following amniocentesis or chorionic villus sampling.
RP may be inherited in an autosomal dominant, autosomal recessive, or X-linked manner. X-linked RP mutations generally only affect men. Genetic counseling should be provided to affected individuals and their families once the mode of inheritance has been determined through family history or molecular testing. Identical mutations may however produce different clinical manifestations. In X-linked familial cases, carrier testing for female relatives can be performed.
Management and treatment
Treatment is primarily aimed at slowing progression of the disease. Vitamin A palmitate and lutein-DHA may be provided as protecting antioxydants. Oral acetazolamide or topical dorzolamide are used to reduce cystoid macular edema. Lens extraction is required when cataracts reduce visual acuity. Sunglasses with short wavelength filtering improve visual performance and optical aids are recommended. Rehabilitation for reading and moving can be proposed in end-stage patients.
Except for mild cases or sectorial RP, most cases progress to legal blindness (visual acuity < 1/20 and visual field < 5 degrees).