Coats disease

Coats disease is also known as Coats' disease, retinal telangiectasis, unilateral retinal telangiectasis, idiopathic retinal telangiectasia, primary (congenital) retinal telangiectasia, OMIM 300216.

It is a sporadic idiopathic disorder characterized by abnormal retinal vascular development (retinal telangiectasis) that results in vessel leakage, subretinal exudation, and retinal detachment.

Severity can range from slight vision loss to total retinal detachment and blindness. Coats disease belongs to the group of vitreoretinal dystrophies and was first reported by G. Coats in 1908.

Epidemiology

Coats disease is a very rare eye disorder. The exact prevalence is unknown. There is a clear male predominance (more than 75% of patients) and no ethnic predisposition.

Onset and clinical features

Onset

The onset of symptoms generally appears in the first decade of life and the mean age of onset is 5 years. Less common adult form with onset after the age of 35 years has also been described.

Clinical features

The classic "childhood/adolescent" form of Coats disease is isolated, unilateral and almost invariably seen in males. The typical presenting signs include blurred vision, unilateral decreased vision (visual acuity of 20/200 or worse), strabismus and/or leucocoria. Deterioration in either central or peripheral vision is the main symptom. Photopsia and floaters are common. Persistent color patterns may also be perceived.
Often, the unaffected eye compensates for the loss of vision in the other eye; however, this may result in some loss of depth perception and parallax.

The hallmark of the disease is the development of telangiectasia in the retinal periphery which can lead to massive subretinal exudation and retinal detachment. In more than 50 % of cases, the telangiectasias are found anterior to the equator, with predilection for the temporal and inferior quadrants. In addition to telangiectasis, there may be capillary nonperfusion, aneurysmal formation, and massive lipid deposition.

At advanced stages, retinal detachment is likely to occur. Secondary cataracts can also develop. The natural history is variable but typically progressive. Patients who develop extensive exudative retinal detachment commonly progress to total retinal detachment, neovascular glaucoma, and phthisis bulbi. It seems that the earlier age of presentation correlates with more severe disease course and progression. The presenting visual acuity also correlates with the long-term prognosis. Risk factors predictive of poor visual outcome include postequatorial, diffuse, or superior location of the telangiectasias and exudation, failed resolution of subretinal fluid after treatment, and presence of retinal macrocysts.

In rare cases, Coats disease can bee initially diagnosed in adulthood, with clinical manifestations similar to those diagnosed in childhood. These patients are often asymptomatic or present with good vision, and did not have leukocoria, extensive areas of exudation, or retinal detachment.
In adult patients, vascular abnormalities appeared in the equatorial and peripheral regions in all the patients and also in the juxtamacular region in the vast majority. Adult-onset cases are frequently associated with elevated serum cholesterol and generally have slower disease progression.

Coats disease is isolated in the majority of cases, although associations with facioscapulohumeral muscular dystrophy, Senior-Loken syndrome and multiple glomus tumors have been described.

Etiology and pathogenesis

The etiology remains poorly understood.

Recent data indicate the causative role of somatic mutation in the NDP gene. NDP mutations also give rise to other vitreoretinal diseases, including Norrie disease, familial exudative vitreoretinopathy (FEVR), and retinopathy of prematurity (ROP). Common to all four diseases are defects in the vascularization of the retina.

Diagnosis

Diagnosis is based on the clinical characteristics and careful funduscopic examination. Fluorescein angiography is a most helpful tool in making diagnosis. Ancillary testing, ultrasound, computed tomography and optical coherence tomography can be used for further evaluation.

Staging classification applicable to diagnosis, treatment and ocular prognosis has been proposed: Stage 1: Retinal telangiectasia only; Stage 2: Telangiectasia and exudation A. Extrafoveal exudation B. Foveal exudation; Stage 3: Exudative retinal detachment A. Subtotal detachment 1. Extrafoveal 2. Foveal B. Total retinal detachment; Stage 4: Total retinal detachment and glaucoma; Stage 5: Advanced end-stage disease approaching phthisis.

Differential diagnosis

Differential diagnosis may vary depending on the stage at presentation. The most important differential diagnosis is unilateral retinoblastoma, which occurs in the same age group and has some overlapping ophthalmoscopic and clinical manifestations.

Other differential diagnoses include Norrie disease, FEVR, ROP, persistent hyperplastic primary vitreous (PHPV), retinal capillary hemangioma, retinal cavernous hemangioma, incontinentia pigmenti, idiopathic juxtafoveal telangiectasis, and toxocariasis.

Management

The primary goal of treatment in Coats disease is to eradicate retinal telangiectasia, and preserve the globe and the vision.

Treatment should be tailored according to the disease's severity and staging. In children older than 15 years and in young adults, Coats disease is generally less aggressive; thus close observation only may be appropriate. In these patients, treatment should be considered in case of documented progression.

Argon laser photocoagulation is the treatment of choice in the early stages. Cryotherapy is also an important modality for treating peripheral telangiectasias associated with extensive exudation or subtotal retinal detachment. On an average, three to four sessions of treatment are required to control the disease process. Both techniques become less effective once the retina is detached and when more than two quadrants are affected.

In rare cases, a vitrectomy may be necessary to settle the detached retina. Steroid injection or vascular endothelial growth factor (VEGF) inhibitors (e.g. bevacizumab) may be used as adjunctive treatment.

Enucleation may be indicated in cases with extensive exudative retinal detachment and secondary neovascular glaucoma.ary hemangioma, retinal cavernous hemangioma, incontinentia pigmenti, idiopathic juxtafoveal telangiectasis, and toxocariasis.

Follow-up and prognosis

Follow-up

Regular life-long follow-up by an ophthalmologist every 6 months should be offered to all individuals with Coats disease.

Prognosis

Stabilization of the disease course or clinical improvement can be achieved in approximately 75 % of the cases, using a carefully selected therapy. However, recurrence of the telangiectasia and retinal exudation after successful treatment is possible, as found in 7 % of cases after a mean of 10 years in a retrospective consecutive series of 150 patients. This stresses the importance of a long-term follow-up of the affected patients.

References

Pomerleau D, Michael J. Coats' Disease: Diagnosis And Management. Rev Ophthalmol. 2009 December; 16:12.

Shields JA, Shields CL, Honavar SG, Demirci H, Cater J. Classification and management of Coats disease: the 2000 Proctor Lecture. Am J Ophthalmol. 2001 May;131(5):572-83.

Smithen LM, Brown GC, Brucker AJ, Yannuzzi LA, Klais CM, Spaide RF. Coats' disease diagnosed in adulthood. Ophthalmology. 2005 Jun;112(6):1072-8.

Sims, Katherine B. NDP-Related Retinopathies. July 23, 2009. NCBI Bookshelf GeneReviews. [http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene∂=Norrie].

Contributors:

Katia Marazova, MD, PhD (January 2010), Prof. José Alain Sahel, MD, PhD and Dr Caroline Laurent-Coriat, MD, PhD

Disclaimer: This document contains information based on published scientific articles and is for educational purposes only. It is in no way intended as a substitute for qualified medical professional help, advice, diagnosis or treatment.