Case of the Month

Edited by Robert N. Johnson, MD

Figure 1: Color photo montage of the left eye. Note the circinate lipid temporal to the macula and areas of aneurysmal and telangiectatic vessels inferotemporally

Case History

A 57-year-old female presented with the complaint of recent onset blurry vision in the left eye. She had no past ocular history. Past medical history was unremarkable, including no history of systemic hypertension, diabetes mellitus, or radiation therapy. Family history and review of systems were noncontributory.

On examination, her best-corrected visual acuity was 20/20 in the right eye and 20/40 in the left eye. Ocular motility, pupillary examination, intraocular pressure, and anterior segment examinations were normal in both eyes.

The posterior segment examination of the right eye was unremarkable. In the left eye, however, there were multiple aneurysmal dilatations and telangiectatic changes located inferotemporally, with associated circinate lipid as well as macular edema (Figure 1).

Fluorescein angiography revealed normal retinal circulation in the right eye, and multiple telangiectatic and aneurysmal changes with diffuse leakage in the left eye (Figure 2). Optical coherence tomography (OCT) scan of the left eye revealed macular edema (Figure 3).

Figure 2: Fundus angiogram montage of the left eye. Note the aneurysmal and telangiectatic changes inferotemporal to the left fovea

Figure 3: SD-OCT of the left macula. Note the retinal edema with intraretinal hyperreflective changes secondary to lipid exudation.

Differential Diagnosis

Retinal vein occlusion, diabetic retinopathy, radiation retinopathy, hypertensive retinopathy, retinal vasculitis, Coats disease.

Clinical Course

Based on the classic clinical findings and lack of potentially associated ocular comorbidities or systemic conditions, a diagnosis of Coats disease was made. As the patient had vision loss due to exudation from abnormal telangiectatic vessels, focal laser treatment was recommended. Following focal laser treatment, vision improved and the exudation resolved over the course of several months. At 3-year follow up, vision was 20/20 in the left eye with no evidence of new exudation (Figure 4 and 5).

Figure 4: Optos photo of the left eye, 3 years following focal laser treatment to areas of leakage. Note the pigmented scar and resolution of the macular edema and lipid exudation.

Figure 5: Optos wide angle fluorescein angiogram. Note the laser scars inferotemporal. Very mild residual telangiectatic changes are seen further temporally.

Discussion

Coats disease was first described by in 1908 by George Coats, a Scottish ophthalmologist.¹ It is characterized by idiopathic retinal telangiectasias and exudation, which are most typically unilateral and more common in males.

Coats disease is usually diagnosed at a young age, often presenting with leukocoria or xanthocoria. In the Shields’ series of 150 patients with Coats disease, the mean age at diagnosis was 5 years, and it was 3 times more common in males than females and unilateral in 95% of cases.² Typical findings in children include telangiectatic and aneurysmal vascular abnormalities with surrounding capillary non-perfusion and associated intra-retinal exudation. Pediatric patients can also present with exudative retinal detachments and in these cases especially, Coats disease must be differentiated from retinoblastoma.

Coats disease in adults tends to be a milder. In the Smithen et al. series, which included patients diagnosed with Coats disease after the age of 35, the disease was again characterized by idiopathic telangiectasias, aneurysms, and retinal exudation.³ 92% of cases were male. The patients were often asymptomatic and presented with good visual acuity. They also often did not have extensive areas of exudation, as can be seen in pediatric cases. In typical pediatric cases of Coats, furthermore, the vascular abnormalities tend to be in the far periphery, whereas in the adult patients from this series, the abnormalities were typically equatorial. Few developed exudative retinal detachments. Interestingly, Coats disease patients at any age can develop macular fibrosis, sometimes referred to as a subfoveal nodule, which may represent a neovascular process.⁴

Coats disease in adults must be differentiated from what is sometimes referred to as “Coats response”, a retinal vascular condition which mimics Coats disease but is secondary to diseases such a retinal vascular occlusion, radiation, or intraocular inflammation.¹

The etiology of Coats disease is unknown, however investigations have suggested a genetic basis. A mutation in the Norrie disease pseudoglioma (NDP) gene—which encodes Norrin, a retinal protein—has been implicated.⁵ Coats disease in adults has also been reported in association with hypercholesterolemia.⁶

In the Yannuzzi and Blodi classification system of idiopathic macular telangiectasia,⁷ which represents a revision of the model proposed by Gass,^8-9 Type 1 macular telangiectasia (aneurysmal telangiectasia) is considered to be a form of Coats disease limited to the macula. Type 2 macular telangiectasia (perifoveal telangiectasia), in contrast, is bilateral, limited to the perifoveal area, and lacks prominent aneurysms or lipid accumulation.

Adult Coats patients presenting without exudation can be monitored without treatment. If exudation develops, treatment strategies include ablation of telangiectatic vessels and areas of non-perfusion with focal laser or cryotherapy.¹ Anti-VEGF therapy, alone or in combination with photodynamic therapy, has also been used with reported success.^10-11

References

1. Ryan S. Retina, 5th ed. 2013:1058-1070.
2. Shields JA, Shields CL, Honavar SG, et al. Clinical variations and complications of Coats disease in 150 cases: the 2000 Sanford Gifford Memorial Lecture. Am J Ophthalmol 2001;131:561-571.
3. Smithen LM, Brown GC, Brucker AJ, et al. Coats disease diagnosed in adulthood. Ophthalmology 2005;112:1072-1078.
4. Jumper JM, Pomerleau D, McDonald HR, et al. Macular fibrosis in Coats disease. Retina 2010;30:S9-14.
5. Black GC, Perveen R, Bonshek R, et al. Coats disease of the retina (unilateral retinal telangiectasis) caused by somatic mutation in the NDP gene: a role for norrin in retinal angiogenesis. Hum Mol Genet 1999;8:2031-2035.
6. Yeung J, Harris GS. Coats disease: A study of cholesterol transport in the eye. Can J Ophthalmol 1976;11:61-68.
7. Yannuzzi LA, Bardal AMC, Freund KB, et al. Idiopathic macular telangiectasia. Arch Ophthalmol. 2006;124:450-460.
8. Gass JD, Owakawa RT. Idiopathic juxtafoveolar retinal telangiectasis. Arch Ophthalmol. 1982;100:769-780.
9. Gass JD, Blodi BA. Idiopathic juxtafoveolar retinal telangiectasis: update of classification and follow-up study. Ophthalmology. 1993;100:1536-1546.
10. Goel N, Kumar V, Seth A, et al. Role of intravitreal bevacizumab in adult onset Coats disease. Int Ophthalmol 2011;31:183-190.
11. Kim J, Park KH, Woo SJ. Combined photodynamic therapy and intravitreal bevacizumab injection for the treatment of adult Coats disease: a case report. Korean J Ophthalmol 2010;24:374-376.