Treatment of Morvan's Syndrome
Immunotherapy is the cornerstone of treatment for Morvan's syndrome, with plasma exchange, intravenous immunoglobulin (IVIG), and corticosteroids as first-line therapies, followed by rituximab in refractory cases. 1
Understanding Morvan's Syndrome
Morvan's syndrome is a rare autoimmune disorder characterized by:
- Peripheral nerve hyperexcitability (neuromyotonia, myokymia)
- Central nervous system involvement (encephalopathy, confusion, hallucinations)
- Autonomic dysfunction (hyperhidrosis, blood pressure fluctuations)
- Severe insomnia and agitation
- Association with antibodies against voltage-gated potassium channel (VGKC) complex proteins, particularly CASPR2 1
The condition is sometimes associated with thymoma (in approximately 50% of cases) and may present as a paraneoplastic syndrome 2.
Treatment Algorithm
First-line Therapies
Identify and treat underlying causes:
- Thymoma screening with chest imaging
- Thymectomy if thymoma is present (may be curative in some cases) 2
Acute immunotherapy (initiate promptly):
Second-line Therapy for Refractory Cases
- Rituximab: For cases not responding to first-line therapies 4
- Standard dosing: 375 mg/m² weekly for 4 weeks
- Has shown dramatic and lasting response in refractory cases
Maintenance Therapy
- Oral immunosuppressants:
- Azathioprine (2-3 mg/kg/day) with prolonged oral steroid taper 3
- Consider mycophenolate mofetil as an alternative
Symptomatic Management
- For neuromyotonia/myokymia: Anticonvulsants (carbamazepine, phenytoin, or sodium valproate)
- For insomnia: Benzodiazepines or other sleep aids
- For autonomic symptoms: Supportive care based on specific manifestations
Special Considerations
Monitoring and Follow-up
- Regular clinical assessment for symptom recurrence
- Monitoring of antibody titers (VGKC/CASPR2) where available
- Surveillance for thymoma recurrence if previously identified
Treatment Challenges
- Post-thymectomy flare: Some patients experience worsening of symptoms after thymoma removal, requiring intensive immunotherapy 3
- Relapses: May occur and typically respond to repeated courses of IVIG 3
Prognosis
The prognosis is variable and depends on:
- Presence of underlying malignancy
- Promptness of immunotherapy initiation
- Response to treatment
Clinical Pearls
- Early recognition and prompt treatment are crucial for better outcomes
- Testing for CASPR2 antibodies should be performed in suspected cases to confirm diagnosis 5
- Fatal outcomes have been reported, particularly in cases with delayed diagnosis or inadequate treatment 5
- Patients may require ICU management during severe exacerbations due to autonomic instability and encephalopathy 3
The treatment approach should be aggressive, particularly in cases with severe autonomic dysfunction or encephalopathy, as these features are associated with higher morbidity and mortality.