Coats disease was first described in 1908 and is a rare disorder characterized by abnormal development of the blood vessels in the retina. The retina is a nerve-rich tissue lining the back of the eye that transmits light images to the brain, which allows a person to see. Therefore affected individuals may experience loss of vision due to changes in the retina and, in severe cases, retinal detachment. In almost all cases of Coats disease, only one eye is affected. Rarely, both eyes may be exhibit symptoms however one eye is often affected more than the other. The specific cause of Coats disease is not known.
Coats disease affects males more often than females in a ratio of 3:1. The disorder may occur at any age, but the majority of cases are diagnosed in the first two decades of life. Individuals affected with Coats disease may display few or no symptoms while others may have severe involvement. The most common features at presentation of Coats disease include loss of vision, misalignment of the eyes (strabismus), and/or the development of a white mass in the pupil behind the lens of the eye so that the pupil appears white (leukocoria).
Over time, Coats disease may cause detachment of the retina and substantial loss of vision. Additional signs may appear as Coats disease progresses, including elevated pressure inside the eye (glaucoma), clouding of the lens of the eye (cataract), reddish discoloration in the iris due to the growth of new blood vessels in the iris (rubeosis iridis or neovascular glaucoma), shrinking of the affected eyeball (phthisis bulbi), and/or inflammation of eye (uveitis).
Eye symptoms result from a developmental malformation, known as telangiectasia, of the blood vessels in the retina. Telangiectasia (tele equals far or end, angio means blood vessel, and ectasia refers to dilation) occurs when there is abnormal widening of groups of small blood vessels, resulting in the leakage of proteins and lipids from the blood. When this occurs in the retina, it is termed exudative retinopathy. This leakage can lead to retinal detachment and the other symptoms discussed above.
The specific cause of Coats disease is not known. One hypothesis in the literature is that a mutation of the Norrie disease protein (NDP) gene leads to Coats disease. This gene is an attractive candidate because it has been shown to play a vital role in retinal blood vessel development. One study showed some promise for involvement of the NDP gene in Coats disease, however further studies have not been able to verify this hypothesis. In general, Coats disease is considered a non-genetic, non-heritable condition.
It is estimated that about 69% of those affected are male. The average age at diagnosis is 8-16 years, although the disease has been diagnosed in patients as young as 4 months. About two-thirds of juvenile cases present before age 10. Approximately one-third of patients are 30 years or older before symptoms begin.
A diagnosis of Coats disease is made based upon a thorough clinical ophthalmic evaluation, a detailed patient history, and specialized tests, including retinal fluorescein angiography, diagnostic echography, and in some cases computed tomography imaging of the orbits.
The treatment of Coats disease is directed toward the specific signs present in each individual. A procedure that uses extreme cold to create a scar around the abnormal blood vessels (cryotherapy), and/or a procedure that uses laser energy to heat and destroy abnormal blood vessels (photocoagulation) are used singly or in combination to treat Coats disease. In conjunction with these procedures, steroids or other medicines such as bevacizumab may be injected into the eye to control inflammation and leaking from blood vessels. Surgery to reattach the retina may also be necessary.
Genetic counseling is not necessary if the diagnosis is accurate since this is a non-genetic malformation and the recurrence risk is the same as the background rate in the general population.
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