What is Coats disease (Coats syndrome)?

Coats' Disease (Coats Syndrome)

Coats' disease is an idiopathic, non-hereditary retinal vascular disorder characterized by retinal telangiectasia, aneurysms, and abnormal leakage from these vessels leading to intraretinal and subretinal exudation, typically presenting unilaterally in young males during the first decade of life. 1, 2

Epidemiology and Clinical Characteristics

• Coats' disease predominantly affects males with no significant ethnic disparities, classically presenting between ages 4-8 years, though most cases are diagnosed in the first and second decade of life. 1, 3
• The condition is sporadic and isolated, with no associated systemic abnormalities or hereditary pattern. 2, 4
• Unilateral involvement is typical, though bilateral cases can rarely occur. 1, 2
• Younger patients at presentation have more severe disease and poorer visual outcomes. 2

Pathophysiology

• The pathogenesis is multifactorial, involving inflammatory, vascular, and potentially genetic components. 3
• Ischemic retinal areas elevate VEGF levels, promoting angiogenesis and impairing the blood-retinal barrier, leading to the characteristic vascular abnormalities and exudation. 3
• The disease involves abnormal development of retinal vessels (telangiectasia) with progressive deposition of intraretinal or subretinal exudates, which can lead to exudative retinal detachment. 1

Clinical Presentation

• Early stages are asymptomatic, but the disease progresses to reduced visual acuity, strabismus, and leukocoria. 3
• Advanced presentations include extensive lipid exudation in the macula, telangiectatic vessels with microaneurysms, and vascular malformations. 4
• Severe cases can lead to blindness, painful red eye, or ocular atrophy, particularly with early childhood onset. 3
• Adult-onset cases are rare but have been documented, presenting as late as the third decade of life. 4

Diagnostic Evaluation

Essential Imaging Studies

• Fundus photography and fluorescein angiography are diagnostic, demonstrating leakage from telangiectatic vessels and the extent of vascular abnormalities. 5, 4
• Optical coherence tomography (OCT) detects macular edema and vitreoretinal interface changes with high resolution. 4
• OCT angiography (OCTA) identifies reduced blood flow density in capillary networks, providing additional diagnostic information. 3
• Ultrasonography, CT scan, and MRI are reserved for advanced stages when differentiation from retinoblastoma is necessary. 1

Key Differential Diagnoses

According to the American College of Radiology, Coats' disease shows absence of calcification and occurs in normal-sized globes, distinguishing it from retinoblastoma (which shows calcification) and Persistent Hyperplastic Primary Vitreous (which shows microphthalmia). 6

Management Strategy

Early-Stage Disease

• Laser photocoagulation of abnormal leaking retinal vessels is the primary treatment for early stages. 1, 2
• Cryotherapy is effective for peripheral vascular abnormalities in early disease. 1, 2
• Limiting treatment only to the primary Coats lesions is a minimally invasive strategy that preserves normal capillaries, as diffuse exudation from normal retinal capillaries resolves with treatment of focal primary lesions. 5

Advanced Disease

• Intravitreal anti-VEGF agents (bevacizumab, ranibizumab) serve as important adjuvant treatment for macular edema alongside traditional management options. 2, 4
• Surgical techniques including pars plana vitrectomy and transscleral drainage are required for retinal detachment in advanced stages. 1, 3
• Combined therapy with intravitreal anti-VEGF injections and sectoral laser photocoagulation achieves good outcomes in cases with significant macular edema and peripheral vascular abnormalities. 4

Prognosis

• Prognosis depends heavily on the stage at presentation, with early detection and intervention preserving vision. 3
• Younger age at presentation, advanced stage, and severe manifestations are associated with more aggressive progression and poorer outcomes. 3
• Stabilization or clinical improvement can be achieved using carefully selected therapy based on disease stage. 1
• Over the decades, management has shifted from enucleation to conservative approaches, achieving good outcomes with modern treatment modalities. 2