Stargardt's disease
Stargardt's disease, also known as fundus flavimaculatus, is the most prevalent form of inherited juvenile macular degeneration. It is primarily inherited through an autosomal recessive pattern, although a smaller percentage of cases may follow an autosomal dominant pattern. Generally diagnosed between the ages of six and twenty, the disease leads to bilateral central vision loss, often identified as central scotomas, while peripheral and night vision usually remain intact. Genetic factors play a significant role, with mutations in the ABCA4 gene linked to the autosomal recessive form and the ELOVL4 gene related to the autosomal dominant form.
Currently, there is no known cure for Stargardt's disease, and individuals are encouraged to avoid bright lights and ultraviolet rays, which may exacerbate the condition. Genetic screening is recommended for families with a history of the disease, as early detection can aid in managing the condition. Diagnostic methods include fluorescein angiography and electrooculography, which help in identifying characteristic retinal changes. Despite the challenges posed by the condition, individuals are encouraged to utilize low vision services to enhance their quality of life.
Stargardt's disease
ALSO KNOWN AS: Fundus flavimaculatus
DEFINITION Stargardt’s disease is the most common form of inherited juvenile macular degeneration. It is almost always inherited through an autosomal recessive mode of inheritance, but up to 10 percent of cases may be inherited in an autosomal dominant mode.
Risk Factors
Stargardt’s disease is an inherited disease; there are no steps that can be taken to avoid developing the disease.
Etiology and Genetics
Stargardt’s disease is usually diagnosed after the age of six but before the age of twenty; however, in some cases, the vision loss may not be noticed until age thirty or forty. According to 2023 statistics from the online journal StatPearls, about 10 to 12.5 people per 100,000 had Stargardt's disease in the United States. In the United Kingdom, the rate was 0.110 to 0.128 per 100,000 people. Men and women are affected with Stargardt’s disease equally. The gene for the autosomal recessive form of Stargardt’s disease was found on the short arm of chromosome 1 and is called the ABCR or ABCA4 gene. The specific gene has been localized to 1p22. This gene produces an ATP-binding transport protein; with the mutated gene, the defective protein is unable to perform its transport function. This protein is expressed in the inner rod segments, and the defect leads to degeneration of these cells in the retina and vision loss.
However, only 60 percent of people with Stargardt’s, or fundus flavimaculatus, have a mutation in the ABCA4 gene. Further research has shown that this locus is involved in the development of age-related macular degeneration, autosomal recessive retinitis pigmentosa, and autosomal recessive rod-cone dystrophy. It is thought that these diseases are part of a continuum.
In autosomal dominant Stargardt’s disease, the defect has been mapped to chromosome 6q16.6 and is associated with the mutation located on the ELOVL4 gene. This gene codes for a membrane-bound protein that is involved in long-chain fatty acid biosynthesis. Other retinal diseases have been traced back to chromosome 6, such as recessive retinitis pigmentosa, Leber congenital amaurosis, and North Carolina macular dystrophy.
Symptoms
The main symptom is bilateral decreased central vision starting in childhood and young adulthood. This vision loss manifests itself as bilateral central scotomas. Color vision is also impacted, but it usually is not noticeable until the later stages of the disease. People with Stargardt’s disease generally do not have any decrease in peripheral vision or any problems with night vision.
Screening and Diagnosis
For people whose parents or genetically related siblings have a diagnosed inherited macular dystrophy, there should be a genetic screening test done to rule out Stargardt’s disease or one of the other related conditions. For many patients, however, this may not be an option, and the disease may be misdiagnosed in the early stages because of lack of changes in the retina. As the disease progresses, there may be yellowish “pisciform” flecks at the level of the retinal pigment epithelium at the posterior pole; a bull’s-eye type pattern of retinal degeneration may also become evident later in the disease. Areas of regional geographic atrophy also give the macula what is known as a “beaten bronze” appearance.
Diagnostic tests that may be used to diagnose Stargardt’s disease include fluoroscein angiography (FA) and electrooculography. In Stargardt’s disease, the FA shows what is known as a dark or silent choroid, irregular hyperfluorescent spots, and the bull’s-eye pattern of retinal degeneration. The electrooculography test tends to be subnormal. Occasionally, visual field tests will be obtained to create a map of the visual field.
Treatment and Therapy
At this time, there is no known treatment for Stargardt’s disease. Because of the role of ABCA4 in the processing of vitamin A, some researchers feel that excess vitamin A might make the disease worse.
Prevention and Outcomes
Genetic screening in couples where one person is known to have the disease or where family members are known to have the disease may help determine if any future children are at risk of developing the disease. It is thought that bright lights and ultraviolet rays may accelerate the progression of Stargardt’s disease, so it is suggested that people with Stargardt’s disease should avoid bright lights and wear UV-blocking sunglasses as much as possible.
An important factor in improving outcomes in people with Stargardt’s disease is to learn about available low vision services and aids that can help a person live a full and functional life.
Bibliography
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Hartnett, Mary Elizabeth, et al. Pediatric Retina: Medical and Surgical Approaches. Illustrated ed. Philadelphia: Lippincott, 2004. Print.
Ho, Allen C., et al. Retina: Color Atlas and Synopsis of Clinical Ophthalmology. Illustrated ed. New York: McGraw-Hill Professional, 2003. Print.
Kohli, Piyush, Koushik Tripathy, and Kirandeep Kaur. "Stargardt Disease." StatPearls, 8 Jan. 2024, www.ncbi.nlm.nih.gov/books/NBK587351/. Accessed 6 Sept. 2024.
Oluleye, Tunji S., et al. "Stargadt's Disease in Two Nigerian Siblings." Intl. Medical Case Reports Journ. 6 (2013): 13–15. Print.
Regillo, Carl D., Gary C. Brown, and Harry W. Flynn. Vitreoretinal Disease: The Essentials. Illustrated ed. New York: Thieme Medical, 1999. Print.
Westenen-van Haaften, Sarah C., et al. "Clinical and Genetic Characteristics of Late-Onset Stargardt's Disease." Ophthamology 119.6 (2012): 1199–210. Print.
Yanoff, Myron, Jay S. Duker, and James J. Augsburger. Ophthalmology. 3d ed. New York: Elsevier Health Sciences, 2009. Print.