A 57-year-old female with a history of IgM lymphoplasmacytic lymphoma presented with malaise, blurred vision, confusion, and headaches.A lumbar puncture revealed lymphocytic pleocytosis,elevated protein,low glucose and positive PCR for HSV-2;she was started on acyclovir. Visual acuity (VA) was 20/40 right eye (OD) and 20/25 left eye (OS), with a trace relative afferent pupillary defect (rAPD) of the right eye and color vision of 2/11 OD and 4/11 OS with Ishihara plates. On hospital day five, her vision  worsened to counting fingers at two feet OD and 20/200 OS with increased disc swelling OU and a more prominent right rAPD. She was started on 1g methylprednisolone for three days. Repeat VA revealed 20/800 OD and 20/40 OS, with a 2+ right APD. Given minimal improvement of vision with steroids,she completed four days of 0.5g/kg/day IVIG, with significant improvement of vision to 20/50 OD and 20/30 OS. Two months later, she had VA 20/20 OU with no rAPD.  Ishihara plates were 11/11 OU. 

There have been two case reports of HSV-associated optic neuritis in the literature, both using corticosteroids alone as the treatment for optic neuritis. Our patient had minimal improvement with corticosteroids so a four-day course of IVIG was initiated, leading to a drastic improvement in her symptoms.

This case highlights that HSV-2 can potentially trigger an inflammatory and/or autoimmune reaction in the CNS leading to vision-threatening optic neuritis.  In such patients, the use of IVIG might be beneficial, especially in cases unresponsive to high dose IV steroid therapy.