GeneDx :: Tests :: Genetic Testing of the ABCA4 Gene in Stargardt Disease, Retinitis Pigmentosa and Cone-Rod Dystrophy

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Genetic Testing of the ABCA4 Gene in Stargardt Disease, Retinitis Pigmentosa and Cone-Rod Dystrophy

ABCA4

Stargardt disease (STGD) / Fundus Flavimaculatus (FFM) ) is the most common autosomal recessive macular dystrophy with an estimated prevalence of 1 in 10,000 individuals. STGD manifests in the first or second decade of life with decreased central vision, progressive bilateral atrophy of the retinal pigment epithelium, and the appearance of orange-yellow flecks distributed in the posterior pole, sometimes extending beyond the vascular arcade. A milder form of the same disorder, fundus flavimaculatus, has a later age at onset, slower progression, and more-widespread distribution of the flecks.

Cone-Rod Dystrophy (CORD) has an estimated prevalence of 1 in 40,000 individuals. Most patients experience visual loss, impaired color vision, and a central scotoma early in life. During the initial stage of disease, the fundus may be normal or show fine macular lesions and pallor of the optic disc. Cone-rod dystrophy is characterized by more severe cone degeneration, which in the electroretinogram (ERG), is distinguished by more distinctive reduction of the photopic cone b-wave amplitude than the scotopic (rod b-wave) amplitude, compared to rod degeneration.

Retinitis Pigmentosa (RP) is a disorder characterized by progressive peripheral vision loss and night vision difficulties (nyctalopia) that can lead to central vision loss. In many cases, the degeneration tends to be worse in the inferior retina. As RP affects predominantly the rod photoreceptors, the scotopic ERG is more severely reduced than the photopic ERG.

Using genomic DNA obtained from a venous blood sample (2-5 mL in EDTA), all 50 exons of the ABCA4 gene and their splice junctions are sequenced using a novel solid-state sequencing-by-synthesis process that allows sequencing a large number of amplicons in parallel. For analysis, DNA sequence is assembled and compared to the published genomic reference sequences. The presence of any potentially disease-associated sequence variant(s) is confirmed by conventional dideoxy DNA sequence analysis. The sequencing test performed at GeneDx is designed to detect all types of mutations found in ABCA4 with the exception of larger intragenic deletions. Targeted array CGH analysis with exon-level resolution (ExonArrayDx) is available to evaluate for a deletion or duplication of one or more exons of the ABCA4 gene.

Information Sheet, including prices and CPT codes
Consent Document
Genetic Test Sample Submission Form (Test Requisition Form) including Payment Options

ABCA4, ABCR, Stargardt disease, cone-rod dystrophy, retinitis pigmentosa, fundus flavimaculatus, macular dystrophy, cone dystrophy, yellow flecks, nyctalopia, night blindness, retina.