What Is Coats Disease?
Source: Genetic and Rare Diseases (GARD) Information Center
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Coats Disease
Retinal Telangiectasia; Exudative Retinitis; Leber Miliary Aneurysm
Coats disease is an eye disorder characterized by abnormal development of the blood vessels in the retina (retinal telangiectasia). This rare disorder was first described by a Scottish ophthalmologist, George Coats, in 1908. Learn about causes, symptoms and treatment.
Coats' disease
Image by Fernandes BF et al.
Coats' disease
Image by Fernandes BF, Odashiro AN, Maloney S, Zajdenweber ME, Lopes AG, Burnier MN Jr.
Source: Genetic and Rare Diseases (GARD) Information Center
Mutation
Image by National Human Genome Research Institute (NHGRI)
Source: Genetic and Rare Diseases (GARD) Information Center
Ideogram of human chromosome X
Image by Office of Biological and Environmental Research of the U.S. Department of Energy Office of Science, the Biological and Environmental Research Information System, Oak Ridge National Laboratory.
The NDP gene provides instructions for making a protein called norrin. Norrin participates in chemical signaling pathways that affect the way cells and tissues develop. Studies suggest that norrin may play a role in Wnt signaling, which is important for cell division (proliferation), attachment of cells to one another (adhesion), cell movement (migration), and many other cellular activities.
Norrin is one of many proteins, or ligands, that can attach (bind) to other proteins called frizzled receptors. These receptors are embedded in the outer membranes of cells. Norrin binds with the receptor frizzled-4 (produced from the FZD4 gene), fitting together like a key in a lock. When a ligand binds to a frizzled receptor, it initiates a multi-step process that regulates the activity of certain genes.
The norrin protein and its receptor frizzled-4 participate in developmental processes that are believed to be crucial for normal development of the eye and other body systems. In particular, norrin seems to play critical roles in the specialization of cells in the retina (the thin layer at the back of the eye that senses light and color) and the establishment of a blood supply to the retina and the inner ear.
Several NDP gene mutations have been found to cause the eye disorder familial exudative vitreoretinopathy. These mutations change single protein building blocks (amino acids) in the norrin protein, altering the normal folding of norrin or preventing it from binding to frizzled-4. The defective norrin disrupts chemical signaling in the developing eye, which interferes with the formation of blood vessels at the edges of the retina. The resulting abnormal blood supply to this tissue leads to retinal damage and vision loss in some people with familial exudative vitreoretinopathy.
More than 115 mutations in the NDP gene have been identified in people with Norrie disease. Norrie disease is an inherited eye disorder that leads to blindness in male infants at birth or soon after birth. NDP gene mutations that cause this condition affect the ability of the norrin protein to bind with frizzled-4, interfering with the specialization of retinal cells for their unique sensory function. As a result, masses of immature retinal cells accumulate in the back of the eyes. Disruption of norrin's role in the establishment of blood vessels supplying the eye eventually causes some of the tissues to break down.
Norrin is also expressed in other systems of the body, and the effects of the disorder can be widespread, including intellectual disability, seizures, behavioral problems, and delayed development. Specific abnormalities and their severity depend on the type and location of the NDP gene mutation. Mutations that delete portions of the NDP gene prevent production of norrin and result in severe problems affecting many body systems in addition to the eyes. Mutations that delete or change single amino acids usually result in less widespread effects.
NDP gene mutations may cause other disorders that affect the retina. One mutation is associated with a disorder called Coats disease. This disorder causes leakage of blood vessels in the retina and retinal detachment, a condition in which layers of the retina separate, resulting in vision loss. Persistent hyperplastic primary vitreous (PHPV) is another retinal disorder that may be caused by NDP gene mutations. In persistent hyperplastic primary vitreous, a remnant of a blood vessel found in the eye before birth remains as a fibrous white stalk between the back of the eye and the lens. Persistent hyperplastic primary vitreous can cause vision loss through retinal detachment, cloudiness of the lens (cataract), or increased pressure inside the eye (glaucoma) that can damage the optic nerve.
In addition, NDP gene mutations may influence the course of a retinal disorder that affects some premature infants. Retinopathy of prematurity is a condition in which abnormal blood vessels appear in the retina and can cause retinal detachment. Babies with retinopathy of prematurity may experience improvement of the condition over time, but some NDP gene mutations have been associated with a worsening of the condition.
Source: MedlinePlus Genetics
Baby and chromosomes - Inheritance
Image by TheVisualMD
Source: Genetic and Rare Diseases (GARD) Information Center
A young child with the yellow eye of coats' disease - still in an early stage. Only visible with a flash camera.
Image by Peter Puype
Source: Genetic and Rare Diseases (GARD) Information Center
Coats' disease
Image by Fernandes BF et al.
Source: Genetic and Rare Diseases (GARD) Information Center
Fluorescein Angiography
Also called: Fluorescein Eye Angiogram, Fundus Fluorescence Photography
Fluorescein eye angiography is a diagnostic procedure that uses orange fluorescent dye (fluorescein) and a special camera to look at blood vessels and the flow of blood inside the eye. The test is particularly useful in the management of diabetic retinopathy and macular degeneration.
Eye Examinations
Also called: Eye Exams, Routine Eye Examination, Standard Ophthalmic Exam, Vision Tests
A standard eye exam is a series of tests done to check your vision and the health of your eyes. Key elements of an eye examination include dilation, tonometry, visual field test and a visual acuity test.
Visual Acuity Test
Also called: Snellen Test
A visual acuity test is an eye exam that checks the smallest letters you can read on a standardized chart (Snellen chart) or a card held 20 feet (6 meters) away. Visual acuity refers to your ability to recognize the shapes and details of the things you see.
Visual Field Test
Also called: Perimetry, Tangent screen exam, Automated perimetry exam, Goldmann visual field exam, Humphrey visual field exam
A visual field test is an eye examination that can detect dysfunction in central and peripheral vision which may be caused by various medical conditions such as glaucoma, stroke, pituitary disease, brain tumors or other neurological deficits.
Color Vision Testing
Also called: Color Blindness Test, Color Perception Test, Ishihara Color Test
Eye care professionals use a variety of tests to diagnose color blindness. These tests can quickly diagnose specific types of color blindness. People with color blindness aren’t aware of differences among colors that are obvious to the rest of us.
Eye Pressure Test
Also called: Intraocular Pressure (IOP) Measurement, Tonometry
Eye pressure, also called intraocular pressure (IOP), is a measurement of the fluid pressure inside the eye. Measuring it is like measuring blood pressure using a method called tonometry. Having eye pressure that’s too low or too high can damage your vision.
Slit-Lamp Exam
Also called: Biomicroscopy, Slit Lamp Exam, Slit Lamp Test
A slit lamp exam is an eye examination using an instrument that combines a low-power microscope with a light source that makes a narrow beam of light. The instrument may be used to examine the retina, optic nerve, and other parts of the eye.
Schirmer Test
Also called: Basal Secretion Test, Dry Eye Test, Tearing Test
A Schirmer test tells your eye doctor how quickly your eyes make tears. Your eye doctor will put a small piece of paper on the edge of your eyelid and see how long it takes for your body to make tears.
Tear Break-Up Time Test
Also called: TBUT
A tear break-up time (TBUT) test checks how long your tear film (layer of tears on your eyes) lasts after you blink. If your tear film does not last long, you may have dry eye.
Ophthalmoscopy
Also called: Funduscopy, Retinal Examination
Ophthalmoscopy is an exam that uses a magnifying lens and a light to check the fundus of the eye (back of the inside of the eye, including the retina and optic nerve). Ophthalmoscopy may be used to check for eye problems, such as glaucoma, macular degeneration, eye cancer, optic nerve problems, or eye injury.
Retinoscopy
Also called: Ret, Shadow Test, Skiametry, Skiascopy
Retinoscopy is an objective determination of the refractive state of the eye (nearsightedness, farsightedness, astigmatism). By using a retinoscope, the amount of correction and the power of lens needed can be determined.
Routine eye exam, rare diagnosis
Image by Courtesy photo
Source: Genetic and Rare Diseases (GARD) Information Center
Photocoagulation
Image by BruceBlaus
Source: Genetic and Rare Diseases (GARD) Information Center
Eye Exam
Image by David Mark
Source: Genetic and Rare Diseases (GARD) Information Center
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