Characteristics of the test: (includes 1 gene)

ABCA4 (OMIM #601691)

Basic characteristics of the clinical phenotype
Stargardt disease (STGD, OMIM #248200) is a juvenile-onset form of macular dystrophy (MD) characterized by degeneration of photoreceptor cells in the macula. As a result, there is severe impairment of central vision and a variable phenotype in terms of age of onset and severity. STGD is among the most common childhood macular degenerations, accounting for about 7% of all retinal degeneration cases and an incidence of 1 in 10,000. The carrier rate is approximately 2%.

The clinical picture in those affected includes a wide range of pathological changes such as progressive bilateral macular degeneration, distinctive pale yellow spots called drusen, disorders in the retinal pigment epithelium, choroidal neovascularization. Macular degeneration develops as part of the body's natural aging process.
STGD is a genetically heterogeneous disease that is usually inherited in an autosomal recessive pattern, but autosomal dominant mutations have also been found. The first gene identified, as well as the gene with the most mutations leading to macular degeneration, is the ABCA4 gene. ABCA4 encodes the retinospecific ATP-binding transmembrane transporter found in photoreceptor outer segment discs and is responsible for the transport of retinoids from photoreceptors to the retinal pigment epithelium. Mutations in this gene lead to disturbances in transortion and accumulation of lipofuscin, toxic to the pigment epithelium, resulting in degeneration of photoreceptors.

Accumulation of lipofuscin in the macular region is characteristic of aging eyes and is a hallmark of both STGD.
Mutations in the ABCA4 gene are also responsible for other retinopathies, such as Cone-rod dystrophy (CORD), Retinitis pigmentosa, RP.

Reasons for referring:
All patients with symptoms of MD, STGD, CORD, RP.

Interpretation of results:
· Identification of point mutations and small deletions/insertions in the ABCA4 gene will allow a genetic diagnosis of ABCA4-related retinopathy (MD, STGD, CORD, RP).
· 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 involves bi-directional DNA sequencing of all coding exons and intron-exon boundaries of the ABCA4 gene. The laboratory offers single exon or exon pair sequencing in the patient's relatives to determine the 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.