Objective:

To report a case of anti-IgLON5 disease presenting with generalized myokymia and to evaluate the response to a combined treatment regimen of an FcRn antagonist and oral glucocorticoids.

Approach:

• Patient Presentation: A 53-year-old male with an 8-month history of generalized myokymia, exacerbated by stress, was diagnosed with anti-IgLON5 disease.
• Diagnostic Tests: Laboratory tests showed positive anti-IgLON5 IgG antibodies in serum and CSF, with no significant MRI findings.
• Treatment Regimen: The patient received a combination of an FcRn antagonist (efgartigimod) and oral glucocorticoids after refusing high-dose glucocorticoids.

Key Findings:

• The patient experienced rapid alleviation of myokymia after treatment, with symptoms completely abating within 6 months.
• Antibody titers gradually declined, but mild symptom recurrence occurred at 7 months post-treatment, with positive antibody titers observed at 14 months.

Interpretation:

This case expands the clinical spectrum of anti-IgLON5 disease.

Limitations:

• The case report is based on a single patient, limiting generalizability.
• Long-term efficacy and safety of the treatment regimen remain to be established, and follow-up data is limited.

Conclusion:

The combination of FcRn antagonists and glucocorticoids may be effective in treating myokymia associated with anti-IgLON5 disease.