Characteristics of the test: (includes 3 genes and one hotspot region)

USH2A (OMIM #608400)

CRB1 (OMIM #604210)

RHO (OMIM #180380)

RPGR-ORF15 (OMIM #312610)

Main features of the clinical phenotype
Retinitis pigmentosa (Retinitis pigmentosa, RP, OMIM #268000) is a group of hereditary retinal dystrophies with a worldwide incidence of 1:4000. In this disease, initially the rods are affected, and later the cones. Clinical features associated with most cases of RP include night blindness (nyctalopia), waxy pallor of the optic disc, narrowed blood vessels, presence of pigmentary masses, followed by progressive loss of peripheral vision in daylight and eventual blindness.

Nonsyndromic pigmentary degeneration of the retina is genetically and clinically heterogeneously presented. At least four forms are known so far, depending on the mode of inheritance. This includes autosomal dominant form of RP (adRP), autosomal recessive (arRP), X-linked and digenic. Also, RP may also be inherited in a mitochondrial pattern. Patients with adRP account for about 15–25% of RP cases; arRP – 30%; X-linked RP is the rarest inherited form and is responsible for 10-20% of cases. The most common mutations leading to arRP, such as those in the USH2A and CRB1 genes, account for 10% and 6.5%, respectively. The rhodopsin gene (RHO) is also a good candidate for screening in patients with arRP and established stationary night blindness (CSNB).

Mutations in RPGR cause approximately 80% of cases of X-linked RP. The ORF15 exon is mainly expressed in the retina, and most mutations in RPGR (60%) are found in this exon.

Reasons for referring:

All patients with symptoms of autosomal recessive (arRP) or X-linked retinal pigment degeneration.

Interpretation of results:

· Detection of point mutations and small deletions/insertions in genes from the panel will allow a genetic diagnosis of autosomal recessive or X-linked retinal pigment degeneration.

· Presence of large deletions and insertions cannot be detected by this method. A combination with a suitable CNV analysis (MLPA, aCGH) is recommended for their detection.

· The genetic counselor will interpret and answer all questions about your result.

Method: Sanger sequencing.

The method includes bi-directional DNA sequencing of all coding exons and intron-exon boundaries of USH2A, CRB1, RHO genes, as well as a region of RPGR-ORF15. The laboratory offers single exon or exon pair sequencing in the patient's relatives to determine carrier status in cases where the mutation is known (Test #182).

Sensitivity of the method: 99.5%

What does the test involve?
· DNA isolation and sample storage.
· Direct sequencing of target genes/gene regions to detect pathogenic mutations.
· Forming a written result of the genetic test.
· Diagnostic interpretation of results and genetic counseling.

Biological material: Venous blood or DNA

For more information, please read the "Biological material requirements and shipping information" carefully.