An unusual case of unilateral chorioretinitis and blind spot enlargement associated with asymptomatic West Nile virus infection

PURPOSE: To report a case of unilateral chorioretinitis and acute blind spot enlargement occurring in a patient with asymptomatic West Nile virus (WNV) infection. OBSERVATIONS: A 28-year-old Hispanic woman, residing in Puerto Rico, presented with an 18-month history of photopsia and a visual field disturbance of the left eye. She had no history of other neurologic symptoms or viral-like illness concurrent with the onset of her symptoms. Corrected visual acuity was 20/20 on both eyes. The left fundus revealed multifocal chorioretinitis, at different stages of evolution, several creamy orange lesions on the mid-periphery along with multiple small punched out lesions, some of which were following a curvilinear pattern distribution. Visual field testing revealed physiological blind spot enlargement on the left eye. Serum WNV antibody serology revealed negative IgM (<0.90) and positive IgG (1.58, <1.30 reference). The patient was treated with oral prednisone, 60mg for two weeks, followed by a 13-week taper of therapy, which resulted in normalization of the visual field defect. CONCLUSION AND IMPORTANCE: Our case raises the possibility that ophthalmic manifestations may occur in some patients with asymptomatic WNV infection. It also suggests that acute blind spot enlargement may also be part of the myriad of ophthalmic manifestations present in WNV patients. In such instances where acute blind spot enlargement is present, oral prednisone may result in improvement and subsequent normalization of the visual field defect. Besides, our case provides evidence to suggest that primary WNV transmission is possible in Puerto Rico.