At a glance: Stargardt Disease Symptoms: Vision loss in childhood or adolescence, light sensitivity, color blindness Diagnosis: Dilated eye exam, photos or scans of the retina Treatment: Low vision aids, wearing dark glasses outdoors, avoiding tobacco, occupational therapy What is Stargardt disease? Color fundus photography image from a Stargardt disease patient showing a central macular scar with some pigmentary changes and surrounding perimacular flecks. Stargardt disease is an inherited disorder of the retina — the tissue at the back of the eye that senses light. The disease typically causes vision loss during childhood or adolescence, although in some forms, vision loss may not be noticed until later in adulthood. It is rare for people with the disease to become completely blind. Stargardt disease is also called Stargardt macular dystrophy, juvenile macular degeneration, or fundus flavimaculatus.
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Inherited as an autosomal recessive trait, it is a severe form of MD that begins in late childhood, leading to legal blindness. Stargardt disease is symptomatically similar to age-related macular degeneration, and it affects approximately one in 10, children. Stargardt disease is usually diagnosed in individuals under the age of twenty, when decreased central vision is first noticed. It causes a progressive loss of central vision and, in the early stages, patients may have good visual acuity, but they may experience difficulty with reading and seeing in dim lighting.
Other common symptoms of Stargardt disease include blurriness and distortion. On examination, the ophthalmological findings vary significantly with the progression of the disease. In fundus photos, patients with early Stargardt disease appear to have simple macular degeneration.
Children with the disease typically begin experiencing dark adaptation problems and central vision loss between six and twelve years of age, but symptoms may also first appear in adulthood. As the disease progresses, lipid rich deposits accumulate in the retinal pigment epithelium RPE layer beneath the macula. The RPE is a layer of cells that lies between the retina and the choroid, where it serves the purpose of nourishing the photoreceptor cells.
In advanced Stargardt disease, the buildup of lipofuscin causes atrophy of the macula and the underlying RPE. In late stages of this disease, there may also be color vision impairment. Stargardt disease is almost always inherited as an autosomal recessive disorder, with only ten percent of cases resulting from a dominant mode of inheritance.
Autosomal recessive means that both parents are carriers, having one gene for the disease paired with one normal gene. As a consequence, each of their children has a 25 percent chance of inheriting the two copies of the Stargardt gene one from each parent needed to cause the disease.
Carriers are unaffected because they have only one copy. At this time, it is impossible to determine who is a carrier for Stargardt disease until after an affected child is diagnosed. In , researchers isolated the gene for Stargardt disease. The ABCA4 gene produces a protein involved in energy transport to and from photoreceptor cells in the retina.
Mutations in the ABCA4 gene, which cause Stargardt disease, produce a dysfunctional protein that cannot perform its transport function. As a result, photoreceptor cells degenerate, and vision loss occurs. One of nineteen mutations in the gene causing deletions and substitutions of amino acids has been identified to cause Stargardt disease.
The non-functional ABCA4 protein permits the accumulation of yellow fatty material to accumulate in the retina. This material causes flecks and, ultimately, loss of vision. Further research is needed to find out how the mutated ABCA4 genes affect the biochemistry of the retina and lead to vision loss. This discovery allows researchers to study the underlying biochemical interactions that result from mutations in this gene.
Understanding how genetic mutations lead to retinal degeneration is critical for the development of experimental therapies. Current research also shows that patients with Stargardt disease could slow its progression by wearing UV-protective sunglasses and avoiding exposure to bright light. Researchers have observed that mice which had a mutation of the ABCA4 gene, and which were reared in dark environments had virtually no lipofuscin deposits.
The disease is often misdiagnosed, or not diagnosed in the first few years of onset, and this could be the result of little evidence being found during eye examinations.
The discovery of the Stargardt gene could help in a test for the direct diagnosis of the disease. It is possible that the effect of this newly discovered gene may not be limited only to juvenile MD, in that it could also aid in the search for causes for age-related macular degeneration, the leading cause of vision loss in people over age Also, Advanced Cell Technology announced in November that the FDA approved injection of human embryonic stem cells into the eyes of 12 patients affected by the disease.
The work is based upon research led by Columbia geneticist Rando Allikmets, who discovered the Stargardt gene in Until treatments are developed, it is important that the learning and working environment be adapted for people with Stargardt disease. Appropriate low vision aids and lighting are two important considerations for helping both children and adults to function as normally as possible.
Enfermedad de Stargardt
The main symptom is loss of visual acuity, uncorrectable with glasses. This is manifest as the loss of the ability to see fine details when reading or seeing distant objects. There is a wide variation between individuals in the symptoms experienced as well as the rate of deterioration in vision. Peripheral vision is usually less affected than fine, central foveal vision. Since the advent of genetic testing , the picture has become more complex. What was thought to be one disease is, in fact, probably at least three different diseases, each related to a different genetic change. The severity of the disease is inversely proportional to ABCA4 function and it is thought that ABCA4 related disease has a role to play in other diseases such as retinitis pigmentosa, cone-rod dystrophies and age-related macular degeneration AMD.
Enfermedad de Stargardt