Retinitis pigmentosa (RP) is a group of inherited eye disorders characterized by progressive degeneration of the light-sensitive cells in the retina, leading to vision loss. The retina is the tissue at the back of the eye that converts light into electrical signals, which are then sent to the brain for visual processing. In retinitis pigmentosa, the photoreceptor cells, namely rods and cones, are affected. The worldwide prevalence of this disease is about 1 in 4.000 people.
Retinitis pigmentosa genetic testing is included in Diagnostiki Athinon Monogenic Diseases Genetic Testing along with approximately 100 other inherited diseases, including cystic fibrosis (71 mutations) and hereditary breast cancer (genes BRCA1 415 mutations & BRCA2 419 mutations).
The key points about retinitis pigmentosa are:
- Symptoms: The symptoms of retinitis pigmentosa typically begin with difficulty seeing in low light conditions (night blindness) and the gradual loss of peripheral vision. Over time, central vision may also be affected, leading to significant visual impairment or blindness.
- Genetic Basis: Retinitis pigmentosa is primarily caused by genetic mutations, and it can be inherited in an autosomal dominant, autosomal recessive, or X-linked manner. The genetic diversity of retinitis pigmentosa contributes to variations in the age of onset, rate of progression, and specific symptoms among affected individuals.
- Diagnosis: An ophthalmologist can diagnose retinitis pigmentosa based on a thorough eye examination, visual field testing, electroretinography (ERG) to measure the electrical responses of the retina, and genetic testing to identify specific mutations.
- Treatment: There is no cure for retinitis pigmentosa, but ongoing research explores various therapeutic approaches. Some treatments aim to slow down the progression of the disease, manage symptoms, or provide support for individuals with retinitis pigmentosa. This may include low-vision aids, orientation and mobility training, and genetic counseling. Researchers are investigating potential treatments such as gene therapy, stem cell therapy, and other approaches to address the underlying genetic causes of RP. Clinical trials are ongoing to test the safety and efficacy of these experimental treatments.
Retinitis pigmentosa is a heterogeneous group of inherited ocular disorders that result in progressive retinal degeneration. Mutations in several genes can cause this disorder. This test analyzes several mutations in the USH2A (where the most frequent retinitis pigmentosa-causing mutations occur), FAM161A, and PDE6B genes.
The USH2A gene encodes for the usherin protein, a protein essential for maintaining the function of the retina's photoreceptors and the inner ear's cells. The c.2299delG mutation in the USH2A gene accounts for 16-44% of all variants identified in patients with nonsyndromic RP. The allele frequency of this mutation is 0.34% in individuals of Latin origin and 0.08% in individuals of non-Finnish European origin. This variant, together with p. Cys759Phe or c.2276 G>T in the USH2A gene, is the most frequent in European patients. The p.Cys3358Tyr or c.10073 G>A mutation has also been observed in several patients, and its allele frequency is 0.05% in Europeans.
Another mutation in the USH2A gene is the p.Cys3358Tyr or c.10073 G>A.
Another gene implicated in the development of retinitis pigmentosa is FAM161A. The function of the protein encoded by the FAM161A gene is not yet known, but it is known to be found in the retina at high levels. The pathogenic mutation c.1355_1356del or p.Thr452fs has been identified in homozygosity and compound heterozygosity in different families. This mutation has been considered a founder mutation in the Israeli Jewish population. Perhaps the most common mutation in the Israeli Jewish population.
Lastly, the PDE6B gene encodes one of the subunits of the PDE6 protein complex, which is involved in transmitting and amplifying visual signals. The mutation c.2419Tgt;A or p.Trp807Arg was described in a large Tunisian inbred family. The family members also had Usher II syndrome, and it was observed that the members who were homozygous for the c.2419Tgt;A mutation and for the Usher II syndrome-causing mutation in the GPR98 gene had a more severe ocular phenotype.
Retinitis pigmentosa genetic testing analyzes the 52 most frequent pathogenic mutations of the USH2A gene, the 2 most frequent pathogenic mutations of the FAM161A gene, and the 5 most frequent pathogenic mutations of the PDE6B gene.
The technique used for genetic testing analyzes only the gene's specific mutations, which are the most important and frequent in the literature. However, it should be noted that there are likely other gene or chromosomal mutations in the gene to be tested that cannot be identified with this method. Different analysis techniques, such as next-generation sequencing (NGS), can be used for these cases.
