Coats Disease: Symptoms, Types, Causes and Treatment

Coats disease is a rare, eye disorder that can cause significant vision loss, especially in children but also in adults. It’s characterized by abnormalities in the retinal blood vessels, leading to fluid leakage, fatty deposits, and sometimes retinal detachment. Understanding its symptoms, types, causes, and treatment options is vital for patients, families, and clinicians. This comprehensive article synthesizes current research and expert consensus to provide a clear, accessible overview of Coats disease.

Symptoms of Coats Disease

Coats disease can present with a range of visual symptoms, which often depend on the stage and severity of the disease at diagnosis. Early symptoms may be subtle or even absent, but as the disease progresses, vision problems become more pronounced.

Symptom	Description	Prevalence/Notes	Source(s)
Decreased Vision	Blurred or reduced central vision	Most common presenting symptom	1,6
Strabismus	Misalignment of the eyes	Frequent in young children	1,8
Leukocoria	White pupillary reflex (white pupil)	May mimic retinoblastoma	1,8
Asymptomatic	No obvious symptoms	Sometimes found incidentally	1
Retinal Detachment	Separation of retina with vision loss	Advanced disease	1,3,7
Eye Pain/Redness	Discomfort, especially with complications	Associated with glaucoma	8

Table 1: Key Symptoms

Common Presenting Symptoms

Decreased vision is the leading initial symptom in Coats disease, reported in about a third of patients. It occurs when exudates or fluid leakage disrupt the retina’s normal function, especially if the macula (the central part of vision) is involved. Children may not always articulate vision loss, so parents might notice behavioral changes, such as squinting or favoring one eye 1,6.

Strabismus and Leukocoria

Strabismus—misalignment of the eyes—is often noticed by caregivers and may prompt medical attention. Leukocoria, or a white reflection from the pupil, is a particularly concerning sign, as it can resemble retinoblastoma, a childhood eye cancer. This similarity underscores the importance of thorough examination and imaging for accurate diagnosis 1,8.

Advanced Symptoms and Complications

If untreated, Coats disease can lead to severe complications:

• Retinal detachment: Occurs in nearly half of cases, leading to significant vision loss or blindness.
• Neovascular glaucoma: Abnormal blood vessel growth can increase eye pressure, causing pain and redness.
• Other findings: Macular edema (swelling), retinal macrocysts, and sometimes eye pain if secondary glaucoma develops 1,3,8.

Asymptomatic Cases

A minority of patients, particularly in the early stages or with localized disease, may have no symptoms. These cases are often detected during routine eye exams or screenings for other concerns 1.

Types of Coats Disease

Coats disease is not a one-size-fits-all diagnosis. Its presentation, progression, and prognosis can vary widely depending on age, extent of retinal involvement, and severity. Classification helps guide treatment and predict outcomes.

Type/Stage	Features	Typical Age/Onset	Source(s)
Childhood-Onset	Unilateral, progressive, severe in young boys	1st–2nd decade	1,3,7
Adult-Onset	Slower, localized, less vision loss	>35 years	2,11
Stage 1	Retinal telangiectasia only	Any	3,6
Stage 2	Telangiectasia + exudation (2A: extrafoveal, 2B: foveal)	Any	3,6
Stage 3	Exudative retinal detachment (3A: subtotal, 3B: total)	Any	3,6
Stage 4	Total detachment + secondary glaucoma	Any	3,6
Stage 5	Advanced end-stage (phthisis bulbi)	Any	3,6

Table 2: Types and Stages

Childhood-Onset Coats Disease

The classic and most common form of Coats disease presents in children—typically boys in their first or second decade of life. It is usually unilateral and tends to progress more quickly, often leading to severe vision loss if not identified early 1,3,7. Young children may have more extensive retinal involvement and are at greater risk for complications like retinal detachment and neovascular glaucoma.

Adult-Onset Coats Disease

Adult-onset Coats disease is less common but increasingly recognized. It tends to be milder, more localized, and progresses slowly. In adults, vision loss is often less severe, and end-stage complications are rare. The disease typically involves less than half the retina and is more responsive to conservative treatments 2,11.

Clinical Staging

Accurate staging is essential for treatment planning and prognosis. The most widely used classification (Shields) divides Coats disease into five stages 3,6:

• Stage 1: Isolated retinal telangiectasia (abnormal blood vessels), without exudation.
• Stage 2: Telangiectasia with exudation. Subdivided into extrafoveal (2A) and foveal (2B) exudation, indicating whether the macula is involved.
• Stage 3: Exudative retinal detachment. Subtotal (3A) or total (3B) detachment of the retina due to fluid accumulation.
• Stage 4: Total retinal detachment with secondary (often painful) glaucoma.
• Stage 5: Advanced, end-stage disease with a shrunken, non-functional eye (phthisis bulbi).

Visual outcomes worsen with advancing stage at presentation. Early-stage disease responds best to treatment, while advanced stages often lead to poor vision or require removal of the eye 3,6,7.

Causes of Coats Disease

Despite more than a century of clinical observation, the precise cause of Coats disease remains incompletely understood. However, research has provided valuable insights into its underlying mechanisms.

Cause/Mechanism	Description	Evidence/Notes	Source(s)
Idiopathic	No clear systemic or hereditary cause	Majority of cases	1,7,14
Somatic NDP Mutation	Mutation in NDP gene affecting retinal vessels	Identified in some cases	4
Retinal Angiogenesis Defect	Abnormal vessel development/leakage	Leads to exudation	1,4,7
Inflammation/Lipid Metabolism	Possible role in some adults	Rare; not primary cause	9

Table 3: Causes and Mechanisms

Idiopathic Nature

Coats disease is classified as an idiopathic retinal vascular disorder—meaning its cause is not fully known and it occurs sporadically, with no strong evidence for inheritance or systemic association. Most patients have no relevant family history or systemic abnormalities 1,7,14.

Genetic Factors and the NDP Gene

Recent studies have uncovered a possible genetic mechanism in some patients. Somatic (non-inherited) mutations in the NDP gene, which encodes the norrin protein, have been detected in affected retinal tissue. Norrin is vital for normal retinal blood vessel development (angiogenesis). A deficiency can disrupt vascular formation, leading to the leaky, abnormal vessels seen in Coats disease 4.

Notably, these mutations are somatic—meaning they arise after conception and are confined to retinal cells. This explains why Coats disease is typically unilateral and sporadic, as opposed to inherited systemic diseases.

Retinal Vascular Abnormalities

Regardless of the cause, the hallmark of Coats disease is abnormal development and function of the retinal blood vessels. These vessels become dilated, twisted (telangiectasia), and leaky, allowing serum and lipids to seep into and beneath the retina. Over time, this leakage causes exudation, retinal swelling, and eventually separation (detachment) of the retina 1,4,7.

Inflammation and Lipid Metabolism (Rare)

Some rare adult cases have been associated with chronic inflammation, uveitis, or systemic lipid metabolism abnormalities, but these are exceptions and not considered primary causes 9.

Treatment of Coats Disease

Treatment aims to halt disease progression, preserve vision, and prevent complications. The approach depends greatly on the stage and severity at diagnosis, as well as the patient’s age and overall health.

Treatment	Indication/Stage	Notes/Outcomes	Source(s)
Observation	Early, asymptomatic, stable	Close monitoring	3,12,13
Laser Photocoagulation	Early–mid stage, localized	Destroys abnormal vessels	3,6,7,13
Cryotherapy	Mid–advanced, peripheral	Freezes and seals leaky vessels	3,6,7,13
Anti-VEGF Therapy	Adjunct for edema/exudates	Reduces leakage and swelling	7,14,15
Surgery (Vitrectomy/Retinal Detachment Repair)	Advanced detachment	For severe cases	3,7,15
Enucleation	End-stage, painful, blind eye	Removes eye, rare with early Rx	3,7

Table 4: Treatment Modalities

Observation

In very early-stage or minimally symptomatic cases, especially in adults with localized disease, observation with regular follow-up may be appropriate. The goal is to detect any progression early and intervene if necessary 3,12.

Laser Photocoagulation

This is the mainstay for treating abnormal retinal vessels in early to moderate stages. Laser burns seal and destroy the leaking vessels, preventing further exudation and stabilizing vision. It is most effective when the exudation does not involve the central macula or when detachment is not extensive 3,6,7,13.

Cryotherapy

For more advanced cases, or where the abnormal vessels are in the retinal periphery and inaccessible by laser, cryotherapy (freezing treatment) is used. It causes controlled destruction of abnormal vessels and is often combined with other modalities 3,6,7,13.

Anti-VEGF Therapy

Anti-VEGF (vascular endothelial growth factor) agents are newer treatments that reduce vascular leakage and promote absorption of exudates and fluid. They are especially useful in cases with significant macular edema or as adjuncts to laser/cryo. Anti-VEGF therapy can also help manage retinal neovascularization and reduce the risk of secondary glaucoma 7,14,15.

Surgery

Surgical intervention, such as vitrectomy (removal of the vitreous gel) and retinal detachment repair, is reserved for advanced cases with extensive subretinal fluid or total retinal detachment. Surgery aims to reattach the retina and preserve any remaining vision 3,7,15.

Enucleation

Removal of the eye (enucleation) is now rarely required, thanks to modern treatments. It is reserved for blind, painful eyes with no potential for vision, often in advanced stages with neovascular glaucoma or phthisis bulbi 3,7.

Treatment Outcomes and Prognosis

• Early diagnosis and intervention offer the best chance for preserving vision.
• Advanced stages often result in poor vision despite aggressive treatment.
• Long-term follow-up is essential, as recurrences and new areas of telangiectasia can develop 3,6,7,15.

Conclusion

Coats disease is a complex, rare retinal disorder with variable presentation and outcomes. Key takeaways include:

• Symptoms: Early signs include decreased vision, strabismus, and leukocoria; advanced disease can cause retinal detachment and pain.
• Types: Typically seen in young boys as a unilateral, progressive disease, but can present in adults with milder features. Staging guides management and prognosis.
• Causes: Primarily idiopathic, with emerging evidence for somatic NDP gene mutations affecting retinal vascular development.
• Treatment: Individualized based on stage—ranging from observation and laser/cryo to anti-VEGF therapy and, rarely, surgery or enucleation.

Summary Points:

• Coats disease predominantly affects young males and usually involves one eye.
• Early detection and treatment are crucial for preserving vision.
• Staging and classification help tailor management and predict outcomes.
• Advances in laser, cryotherapy, and anti-VEGF treatments have improved prognosis.
• Lifelong monitoring is recommended due to the risk of recurrence or progression.

Understanding the nuances of Coats disease empowers patients, families, and clinicians to recognize symptoms early, pursue appropriate care, and optimize visual outcomes.