INTRODUCTIONEpiretinal gliosis and retinal vascular tortuosity.1 These

INTRODUCTIONEpiretinal membrane is an avascular, fibrocellular membrane that proliferates on internal limiting membrane (inner layer of retina).

Complex epiretinal membranes occur secondary to an ocular disease and show features of retinal contraction and pigmentation. Combined hamartoma of retina and retinal pigment epithelium (CHRRPE) is a benign endophytic tumor of neurosensory retina and retinal pigment epithelium, and show variable degree of pigmentation. It contains abnormal appearing retinal blood vessels, variable degree of traction at the vitreoretinal interface, prominent pre-retinal gliosis and retinal vascular tortuosity.1 These features of CHRRPE can sometimes be confused with the clinical appearance of complex ERM causing a situation of diagnostic dilemma.We herein report an unusual case of complex epiretinal membrane mimicking as CHRRPE lesion associated with sea fan neovascularisation in a case of healed Eales’ vasculitis, highlighting the role of multimodal imaging and histopathology for understanding disease process.

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CASE REPORTA 49-year-old male patient of Indian origin presented with complaints of diminution of vision in both eyes for 1 month, associated with floaters. There was no history of associated trauma. No history of any systemic illness is present. There was no family history of retinitis pigmentosa and hemoglobinopathies like sickle cell anemia. The recorded vision in the left eye (OS) is always lower than the right eye (OD) since early childhood. On examination the visual acuity was 20/30 and 20/200 in right and left eye respectively. Intraocular pressure  was 14 and 12 mm mercury  in right and left eye respectively.

Significant metamorphopsia was present in left eye. On slit lamp examination, the anterior segment was normal in both eyes. There was no evidence of neovascularisation of iris.Fundus examination revealed healthy discs with cup :disc ratio of 0.4:1 and healthy neuroretinal rim in both eyes. Sclerosis of vessels was present in both eyes.

In right eye, retinal neovascularisation elsewhere (NVE) lesions with associated fibrovascular proliferation, were noted temporally and superonasally, associated with resolving pre-retinal hemorrhage. The neovascularisation had a characteristic sea fan configuration. In left eye, a greyish white, elevated, gliotic macular lesion was noted at the fovea associated with multiple sea fan NVEs temporally at posterior pole with old inferior vitreous hemorrhage. There was no evidence of activity of vasculitis process like edema, cuffing and fresh hemorrhage. On fundus fluorescein angiography showed bilateral temporal multiple capillary drop out areas with leaking neovascularisation lesions in sea fan shaped configuration were noted in both eyes. There was associated sclerosis of peripheral vessels.

Swept source optical coherence tomography of the left eye macular region showed distorted vitreoretinal interface with presence of epiretinal membrane. Disorganisation of inner retinal layers associated with thickening of retinal layers was also found. The outer plexiform layer has also altered configuration resembling saw tooth appearance. There was no disturbance in outer retinal layers (external limiting membrane and ellipsoid zone) and retinal pigment epithelium. Right eye showed normal foveal contour with normal foveal thickness. Systemic investigations for finding the etiology of vasculitis like hemogram, montoux test, HRCT chest, TPHA, VDRL, ANA titres, ANCA titres, serum ACE levels and serum calcium were  within normal limits.

A diagnosis of healed vasculitis sequale (most likely Eales’ vasculitis) was made for both eyes with associated complex epiretinal membrane in left eye. Scatter laser was done in both eyes to reduce neovascularisation activity and patient was kept on regular close follow up. The patient underwent left eye intraoperative OCT guided pars plana vitrectomy with epiretinal membrane removal, internal limiting membrane peeling and gas tamponade for his complaints of significant metamorphopsia leading to poor quality of life. Histopathological analysis of peeled membrane revealed glial cells, fibrocytes, macrophages, retinal pigment epithelial cells and collagen fibrils suggesting a diagnosis of complex ERM. DISCUSSIONCombined hamartoma of retina and retinal pigment epithelium (CHRRPE) is a rare benign, congenital lesion which is mostly unilateral. It was first described by Gass in 1973 as a grey lesion usually slightly elevated, involving the RPE, retina and overlying vitreous.3 It is often covered by grey white retinal or pre retinal tissue showing contraction of the inner retinal surface.

.3 They can be macular, peripapillary or peripheral in location. The fluorescein angiography and optical coherence tomography aids in establishing the diagnosis.1,11 Hypofluorescence may be observed in early phase due to blockage in hyperpigmented areas. Microaneurysms and abnormal dilated capillary network may be visible on arterial-venous phase. In late phase, leakage from dilated vessels may be visible. OCT features include retinal disorganisation with saw tooth appearance of the inner retina classically described as ‘mini peaks’ without outer retinal layers disturbance, also known as ‘maxi peaks.’7 Histopathologically the lesion is composed of disorganised glial tissue with proliferating RPE cords or tubules intermixed with blood vessels.

12Epiretinal membranes may be primary (idiopathic) or secondary (associated with inflammation, intraocular surgery, etc.). Foos et al classified  ERM into simple, intermediate and complex based on clinical appearance and etiology. Complex ERM are usually associated with ocular conditions like inflammation, intraocular surgery, old retinal detachment. OCT helps in diagnosis. Fluorescein angiography may show macular dragging, straightening of vessels and vascular tortuosity.

  Sea fan configuration neovascularisation is classically described for proliferative sickle cell retinopathy.2 It may be found in other conditions like retinal vasculitis, retinitis pigmentosa,14 sarcoidosis,15 thrombocytosis16 and rarely chronic old rhegmetogenous retinal detachments.17 In our case, the patient had an grayish, elevated  lesion in macular region of  left eye. Swept Source OCT of the lesion showed features like disorganisation of inner retinal layers with saw tooth configuration of outer plexiform layer with normal outer retinal layer and RPE. The clinical appearance and OCT features are in favour of CHRRPE. However, peripheral fundus evaluation was suggestive of healed vasculitis sequale.  Diagnosis of Eales’ vasculitis was made after ruling out the secondary causes of vasculitis. The patient developed peripheral retinal neovascularisation characteristically sea fan shape in configuration due to retinal ischemia.

The diagnosis of complex ERM is more likely than CHRRPE as CHRRPE  usually present early in first or second decade of life and is not associated with secondary causes like inflammation, retinal detachment, exudation, hemorrhage or choroidal involvement. The histopathological analysis was suggestive of complex ERM post operatively.Shield et al observed that epiretinal membrane with secondary retinal folds and striae was present almost in all cases of CHRRPE.

1 Similar to CHRRPE, ERMs are associated with retinal surface gliosis with retinal vascular tortuosity. Thus, it becomes challenging to differentiate childhood ERMs from CHRRPE lesions since fluorescein angiograms do not assess the intraretinal component of CHRRPE. OCT findings may help in distinguishing CHHRPE lesions from ERMs by presence of omega-shaped disorganization of inner retinal layers, posteriorly bounded by the outer plexiform layer in case of macular CHRRPE lesions.13No reports are available in literature highlighting sea fan neovascularisation in an Eales’ disease patient associated with  secondary complex ERM mimicking as CHRRPE. This report brings out the importance of multimodal imaging in a case of vasculitis which helps in distinguishing closely related disease processes. CHRRPE lesion should be identified as they can mimic posterior segment tumours like retinoblastoma, melanoma.

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