Genetic condition causing vision impairment
Stargardt disease (STGD), or fundus flavimaculatus, is a rare, genetically inherited disease that directly affects the retina of the eye, often resulting in the slow progression of vision loss in children. It may also be referred to as Stargardt macular dystrophy or juvenile macular degeneration. STGD is the most prevalent cause of juvenile macular degeneration, affecting approximately 1 in 10,000 individuals worldwide(1). The most common form of STGD is caused by a genetic mutation of the ABCA4 gene, which results in the gradual deterioration of photoreceptors and vision within the eye. There are many symptoms a person with STGD may experience including spots in the vision, color vision deficits, distortion, blurriness, and loss of central vision in both eyes. Symptoms of STGD typically appear during childhood or adolescence, but in some cases difficulty with eyesight and vision loss may not be identified until later in life.
There are no approved treatments for Stargardt Disease
STGD is an aggressive, uncommon genetic disease with an estimated 150,000 diagnoses worldwide. With less than 40,000 patients in the U.S., STGD is recognized as an orphan disease, subject to the Orphan Drug Act in the U.S. Currently, there is no known therapy or method that exists to slow the advancement of STGD. The disease is recognized as a serious unmet medical need by the Foundation of Fighting Blindness and National Eye Institute.
STGD is characterized by an excessive build-up of toxic vitamin A byproducts (primarily A2E) in the retina. The retina is a thin layer of cells in the back of the eye that transforms light into electrical signals that are then sent to the brain, where vision is interpreted. About 95% of STGD cases are caused by mutations in the ABCA4 gene, which is only expressed in the retina. The ABCA4 gene product is responsible for transporting precursors of A2E to a cellular location where they can be degraded. Mutations of the ABCA4 gene result in accumulation of both the precursors of A2E as well as A2E itself. The build-up of toxic A2E results in the dysfunction and eventual death of specialized cells of the retina. The death of these cells, primarily near the center of the retina, results in the loss of central vision.
(1) Kaplan J, Gerber S, Larget-Piet D et al. A gene for Stargardt's disease (fundus flavimaculatus) maps to the short arm of chromosome 1. Nature Genetics 1993;5(3):308-311.