Coats disease

The cause of Coats disease is not currently known. It has been theorized that somatic mutations (acquired, not inherited) in the NDP gene may lead to isolated cases of Coats disease. However, this has not been proven.

Coats disease has been reported as one feature of several genetic syndromes. In these cases, the underlying cause of each syndrome may be responsible for Coats disease. When Coats disease occurs with additional abnormalities that affect the brain, bones, gastrointestinal system, and other parts of the body, it is called Coats plus syndrome and is caused by mutations in the CTC1 gene.

A diagnosis of Coats disease is often suspected based on the presence of signs and symptoms, and findings on a thorough eye examination. Specialized tests to confirm the diagnosis and rule out other conditions may include retinal fluorescein angiography, diagnostic echography, and in some cases, a CT scan of the orbits, and/or MRI.

Isolated Coats disease is not an inherited condition. Rarely, Coats disease can be a feature of an underlying, inherited genetic syndrome. For example, it is a key feature of a condition called Coats plus syndrome, which is characterized by Coats disease plus abnormalities of the brain, bones, gastrointestinal system, and other parts of the body. Coats plus syndrome is inherited in an autosomal recessive manner.

Coats disease is an eye disorder characterized by abnormal development of the blood vessels in the retina (retinal telangiectasia). Most people begin showing symptoms in childhood. Early signs and symptoms vary but may include vision loss, "crossed eyes" (strabismus), and a white mass in the pupil behind the lens of the eye (leukocoria). Over time, Coats disease may also lead to retinal detachment, glaucoma, and clouding of the lens of the eye (cataracts). In most cases, only one eye is affected. Coats disease is not inherited and the underlying cause is not known. It has been theorized that some cases may be due to somatic mutations (acquired, not inherited) in the NDP gene. Treatment depends on the symptoms present and may include cryotherapy and laser photocoagulation (alone or in combination), steroids for inflammation, and/or surgery for retinal detachment.

The most recently proposed staging classification for Coats disease was developed on based in a large series of affected people. This classification may help in choosing the most appropriate course of treatment as well as predicting the long-term outcome (prognosis) for people with Coats disease:

• Stage 1 - retinal telangiectasia only (dilation of capillaries in the retina)
• Stage 2 - telangiectasia and exudation (escape of fluids and material from blood vessels into surrounding tissues)
  • A - extrafoveal exudation (exudation outside of the fovea, which is a small area in the retina responsible for the acute vision)
  • B - foveal exudation (exudation in the fovea)
• Stage 3 - exudative retinal detachment
  • A - subtotal (partial) detachment
  • 1 - extrafoveal
  • 2 - foveal
  • B - total retinal detachment
• Stage 4 - total retinal detachment and glaucoma
• Stage 5 - advanced end-stage disease (defined as a blind, non-painful eye with a total retinal detachment, often with cataract and phthisis bulbi)

The prognosis varies in each case. Factors that effect the prognosis include the stage of disease at the time of diagnosis, the age at diagnosis, the rate of disease progression, and the effectiveness of treatment.

In some older children and young adults, spontaneous regression (improvement of symptoms) has been reported. Younger children typically have more aggressive disease and often have a total retinal detachment by the time they are diagnosed; these children usually have a poor visual outcome. Some people present with advanced disease which does not benefit from treatment, while others show disease progression despite treatment. While most people respond well to treatment, approximately 25% will become worse and require removal of the eye. An ophthalmologist with knowledge about Coats disease may be able to make a general prediction about the chances of retaining the eye and preserving vision.

The extent of visual impairment varies considerably from person to person. Favorable visual outcomes are more likely to be achieved with early detection and treatment, with combined therapies as needed. Even when treatment is not able to restore sight, it is beneficial in saving the eye.

Treatment for Coats disease depends on the severity in each person. The following treatments (used alone or in combination) may be tried:

• Laser photocoagulation (uses a laser to shrink or destroy blood vessels)
• Cryotherapy (a procedure that uses extreme cold to destroy abnormal blood vessels)
• Intravitreal corticosteroid injections to control inflammation
• Anti-vascular endothelial growth factor (anti-VEGF) injections

More advanced disease with extensive retinal detachment may also require surgical interventions such as vitrectomy, scleral buckling to correct a detached retina, and external drainage of fluids.