Morvan Syndrome Decoded: Rare Autoimmune Disorder Attacks Brain and Nerves

Morvan syndrome represents one of medicine's rarer autoimmune challenges, combining peripheral and central nervous system hyperexcitability in a potentially fatal clinical picture. Originally attributed to infections and later heavy metal toxicity, the disorder's autoimmune basis was only clarified in 1999 when CASPR2 antibodies were identified, fundamentally reshaping understanding of the condition.

The syndrome presents across three overlapping domains. Central nervous system involvement includes confusion, behavioral changes, hallucinations, myoclonus, and profound insomnia. Autonomic features encompass hyperhidrosis, labile blood pressure, hemodynamic instability, and cardiac arrhythmias. Peripheral manifestations include neuromyotonia, myokymia, and painful muscle cramps. Most patients experience only a subset of these symptoms, complicating timely diagnosis.

Diagnosis is confirmed by elevated serum titers for CASPR2 and LGI1 antibodies. MoS is frequently paraneoplastic, with malignant thymoma being the most commonly associated malignancy. Clinicians must distinguish MoS from acquired neuromyotonia and limbic encephalitis, conditions that share overlapping features but require distinct management approaches.

Treatment with therapeutic plasma exchange, often combined with immunosuppression, represents the current standard of care. Outcomes vary considerably: a landmark 2012 case series by Irani et al. reported death in approximately 20% of patients, while a more recent Indian cohort reported only 1 death in 8 patients, suggesting potential improvements in recognition and management.

Epidemiologically, MoS is poorly characterized due to chronic underreporting. Prevalence is under one per million, and the condition displays a striking male predominance, with male-to-female ratios reaching 19:1 in some studies. Improved awareness among neurologists and internists is essential for earlier diagnosis and better survival outcomes.