Retinitis pigmentosa

It is included in a heterogeneous group of hereditary eye diseases that result in progressive degeneration of the retina and cause night blindness.

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

Here we study autosomal recessive non-syndromic RP, which presents with vision disorders and hearing loss. The worldwide prevalence of this disease ranges from 1 in 4,000 to 1 in 3,745 people.

Symptoms

The age of onset of symptoms varies from infancy to adulthood, but photoreceptor degeneration can be detected many years before affected individuals are aware of vision problems.

The visual symptoms of RP arise primarily from the loss of photoreceptors in the retina, both rods and cones. One of the first symptoms to appear is night blindness or nyctalopia, patients may notice that they become disoriented in dim light, or that adaptation to dim light is slow. However, in some cases night blindness may go unnoticed as the disease progresses. RP also produces so-called tunnel vision caused by loss of peripheral vision that causes the field of vision to be significantly reduced over time until only central vision is maintained. However, as the disease develops, central vision is also eventually lost. Other symptoms include sensitivity to bright light, loss of color vision and reduced contrast sensitivity.

Disease management

There is no cure for retinitis pigmentosa. However, there are measures that can help control symptoms and slow the progression of the disease. There are retinal implants that perform the functions of the affected photoreceptor cells. On the other hand, vitamin A supplementation can help slow vision loss; however, high levels of vitamin A can cause liver damage. Fish oil and lutein supplements can also slow vision loss. It is important to protect the retina from ultraviolet rays with sunglasses.

Devices such as magnifiers, telescopes and electronic aids are tools that can assist people with RP, as well as orientation and mobility training can be useful for people with RP to function safely and confidently in their environment.

Genes analyzed

FAM161A PDE6B USH2A

Bibliography

Bandah-Rozenfeld, D., Mizrahi-Meissonnier, L., Farhy, C., et al. Homozygosity mapping reveals null mutations in FAM161A as a cause of autosomal-recessive retinitis pigmentosa. American journal of human genetics. 2010 Sep 10;87(3):382-91.

Hmani-Aifa, M., Benzina, Z., Zulfiqar, F., et al. Identification of two new mutations in the GPR98 and the PDE6B genes segregating in a Tunisian family. European journal of human genetics : EJHG. 2009 Apr;17(4):474-82.

Lenassi, E., Vincent, A., Li, Z., et al. A detailed clinical and molecular survey of subjects with nonsyndromic USH2A retinopathy reveals an allelic hierarchy of disease-causing variants. European journal of human genetics : EJHG. 2015 Oct;23(10):1318-27.

McGee, T. L., Seyedahmadi, B. J., Sweeney, M. O., et al. Novel mutations in the long isoform of the USH2A gene in patients with Usher syndrome type II or non-syndromic retinitis pigmentosa. Journal of medical genetics. 2010 Jul;47(7):499-506.

Pérez-Carro, R., Blanco-Kelly, F., Galbis-Martínez, L., et al. Unravelling the pathogenic role and genotype-phenotype correlation of the USH2A p.(Cys759Phe) variant among Spanish families. PloS one. 2018 Jun 18;13(6):e0199048.

Rivolta, C., Sweklo, E. A., Berson, E. L., et al. Missense mutation in the USH2A gene: association with recessive retinitis pigmentosa without hearing loss. American journal of human genetics. 2000 Jun;66(6):1975-8.

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