Background <p>Optic neuritis (ON) is an inflammatory optic neuropathy characterized by acute vision loss. Primary anti-PLA2R-positive membranous nephropathy, an autoimmune disease, has been reported to be related to neurological diseases. However, the co-occurrence of ON and primary membranous nephropathy (PMN) has not been reported.</p> Case presentation <p>A 57-year-old male presented with acute bilateral vision loss. Laboratory tests indicated proteinuria, hypoalbuminemia, hyperlipidemia, and a significantly increased level of anti-phospholipase A2 receptor antibody (PLA2RAb). Orbital MRI revealed inflammatory changes in the posterior segments of both optic nerves. Following treatments with corticosteroids and immunosuppressants, there was a significant improvement in the patient’s vision and proteinuria.</p> Conclusion <p>This case suggests that early identification and intervention for multisystem autoimmune damages are crucial for improving patient prognosis.</p>