Peripheral Inflammatory Yellow Exudative Retinal Coats-Like Vitreoretinopathy Misdiagnosed as Acute Retinal Necrosis in a Retinitis Pigmentosa Patient after Cataract Surgery

We would like to describe a case with Coats-like exudative vitreoretinopathy after cataract surgery in a patient with retinitis pigmentosa (RP) misdiagnosed as acute retinal necrosis (ARN). A patient with RP underwent cataract surgery that was complicated by macular oedema. Following sub-Tenon's injection of triamcinolone acetonide, evolution was initially favourable. However, 2 months later, after 2 sub-Tenon's injections, the patient complained again of floaters and a drop of visual acuity. Aqueous flare measured by laser flare photometry was increased and posterior segment examination showed vitreitis, posterior haemorrhages and a temporal-inferior peripheral white-yellowish area in left eye. Serology (IgGs) for varicella-zoster virus (VZV) was slightly elevated and more so for toxoplasmosis. The whole clinical context strongly evoked ARN not excluding completely ocular toxoplasmosis. Valacyclovir and clindamycin were introduced without benefit. When examining the extreme periphery of the right fellow eye, discreet yellow lesions were also detected rendering the infectious hypothesis less probable. A vitrectomy finally excluded infectious causes and the diagnosis of Coats-like exudative vitreoretinopathy in a RP patient was retained. Increased flare despite 2 sub-Tenon's injections, the presence of micro-haemorrhages, and peripheral yellow retinal necrotic areas drew our attention away from a well-known albeit rare condition of Coats-like response in RP patients, a diagnosis which has to be considered in such circumstances.