GeneDx :: Tests :: Genetic Testing of the CRX Gene in Cone Rod Dystrophy, Leber Congenital Amaurosis and Retinitis Pigmentosa

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Genetic Testing of the CRX Gene in Cone Rod Dystrophy, Leber Congenital Amaurosis and Retinitis Pigmentosa

Leber Congenital Amaurosis (LCA) is a group of congenital inherited disorders of the retina that leads to severe early infantile blindness before the age of 1 year. Clinical findings include sensory nystagmus, amaurotic pupils, and a pigmentary retinopathy.

Cone-Rod Dystrophy (CORD) presents first as a macular disease or as a diffuse retinopathy with predominance of macular involvement. The clinical signs of CORD reflect the predominant involvement of cones, leading to decreased visual acuity in the first decade of life. However, in some cases, diffuse retinopathy affects simultaneously cones and rods, resulting in both night blindness and loss of visual acuity.

Retinitis Pigmentosa (RP) is a group of disorders involving progressive degeneration of the retina that leads to severe visual impairment in the 5th to 6th decade of life. The disorder usually manifests with decline and loss of night vision during adolescence, followed by loss of side vision in young adulthood, and loss of central vision in later life due to the progressive loss of rod and cone photoreceptors. Common symptoms include night blindness and a decreasing visual field, leading to tunnel vision, legal blindness or, in many cases, complete blindness.

Using genomic DNA obtained from a venous blood sample (1-5 mL in EDTA) or buccal swabs (GeneDx kit only), GeneDx will perform bi-directional sequence analysis of the coding exons and intron/exon boundaries of the CRX gene. The sequencing test performed at GeneDx is designed to detect all types of mutations found in the CRX gene. As mutations resulting in haploinsufficiency have been reported in the CRX gene, it is possible that deletions/duplications of one or more exons of any of these genes may play a role in this disorder. 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 CRX gene.

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