Morvan syndrome is a rare autoimmune disorder involving both peripheral and central nervous systems. Patients typically present with continuous muscle twitching (myokymia), cramps, stiffness, fasciculations and autonomic dysfunction including hyperhidrosis, arrhythmias and blood pressure instability. Central nervous system involvement manifests as insomnia, psychiatric symptoms, memory impairment, and occasionally seizures. We report a 27-yearold man who presented with insomnia, severe myalgia, generalized myokymia, autonomic instability, and anxiety following anabolic steroid use. Nerve conductions revealed repetitive after-discharges and needle electromyography revealed myokymic discharges. Serum was strong positivity for CASPR2 and weak positivity for LGI [1] antibodies. The patient responded well to corticosteroids and intravenous immunoglobulin. This case report highlights a rare autoimmune neurological syndrome potentially triggered by anabolic steroid exposure.

Keywords:Morvan syndrome; CASPR2; Neuromyotonia; Anabolic steroids