Autonomic nervous system dysfunction leading to hyperactivity of the sympathetic nervous system can result in excessive sweating. This case report is about a gentleman who presented with acute hyperhidrosis, a symptom of autonomic dysfunction, which turned out to be a relapse of anti-leucine-rich glioma-inactivated 1 (LGI1) antibody encephalitis. This evidence concerns the gene LGI1 and Abnormal autonomic nervous system physiology.