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HEREDITARY MONOGENIC DISEASES

           

Retinitis pigmentosa

Retinitis pigmentosa (RP) comprises a complex group of inherited dystrophies characterized by progressive degeneration and dysfunction of the retina, primarily affecting photoreceptor and pigment epithelial function. RP may occur alone or as part of a syndrome and may be inherited as a dominant, recessive, or X-linked trait or occur sporadically. The same genetic mutation may cause different symptoms in different individuals, and the same syndrome may be caused by different mutations.

Night and peripheral vision are lost progressively, leading to a constricted visual field and markedly diminished vision in some patients. Retinal degeneration can be seen on ophthalmoscopy as typical bone-spicule deposits or attenuated retinal vessels, or detected in early stages by special tests of retinal function.

A family history of RP is present in about 70 percent of patients. The worldwide prevalence of RP is estimated at 1 in 4000 to 5000. About 100,000 patients are affected in the United States.

Symptoms — The visual symptoms of retinitis pigmentosa (RP) arise primarily from the loss of retinal photoreceptors, both rods and cones.

Night blindness (nyctalopia) is one of the earliest symptoms. Patients may notice that they become disoriented in dim light, or that adaptation to dim light is slow, as in movie theaters. However, night blindness may go unrecognized until the disease is advanced, due to the insidious nature of RP and pervasive artificial light sources; some patients never recognize night blindness as a symptom. Once a patient is suspected of having RP, he should be referred to an ophthalmologist who specializes in hereditary eye disease or to a genetics professional.

Progressive constriction of the visual field is another common feature.

Age of symptom onset ranges from childhood to adulthood, but photoreceptor degeneration can be detected many years before affected individuals are aware of vision problems.

GENE OR REGION STUDIED


  • USH2A
  • FAM161A
  • PDE6B