# Anti-CV2 Antibody-Positive Sensorimotor Polyneuropathy Following Bacillus Calmette-Guérin Intravesical Infusion Therapy

## TL;DR

A man developed nerve-related weakness after a bladder cancer treatment, possibly due to an immune response causing temporary antibody positivity.

## Contribution

This case highlights a rare immune-related side effect of BCG therapy, involving transient onconeural antibody positivity and polyneuropathy.

## Key findings

- A 70-year-old man developed demyelinating sensorimotor polyneuropathy after BCG therapy.
- Anti-CV2 antibodies were transiently positive despite no malignancy detected.
- Symptoms improved with immunoglobulin therapy, and antibody levels normalized six months later.

## Abstract

Bacillus Calmette-Guérin (BCG) intravesical infusion therapy is widely used to control recurrence after transurethral resection of bladder tumors. Herein, we report a case of polyneuropathy with transiently positive onconeural antibodies after BCG bladder infusion therapy. A man in his 70s presented with upper and lower extremity weakness 11 weeks after BCG intravesical infusion therapy, a postoperative therapy for superficial bladder cancer. Nerve conduction studies revealed findings that were consistent with demyelinating sensorimotor polyneuropathy. Anti-CV2 antibody was positive; however, contrast-enhanced computed tomography and positron emission tomography revealed no malignancy. The patient’s symptoms improved with immunoglobulin therapy. Contrast-enhanced computed tomography showed no malignancy, and the anti-CV-2 antibody test result was negative six months after discharge. The immune response to BCG bladder infusion therapy may have caused the transient CV2 antibody positivity and polyneuropathy. The possibility of transiently positive onconeural antibodies after BCG intravesical infusion therapy should be considered.