Objective:

To report a case of Lambert-Eaton myasthenic syndrome (LEMS) associated with small cell lung cancer (SCLC) and highlight the diagnostic challenges and the critical role of anti-SOX1 antibodies in such cases.

Key Findings:

• The patient was seronegative for anti-VGCC antibodies but positive for anti-SOX1 antibodies, indicating a need for alternative diagnostic markers.
• LEMS can present atypically, complicating diagnosis when conventional serological markers are absent, highlighting the importance of anti-SOX1 testing.
• The DELTA-P score is useful for malignancy screening in high-risk patients presenting with LEMS-like symptoms, aiding early detection.

Interpretation:

This case emphasizes the necessity of testing for anti-SOX1 antibodies in patients with LEMS, especially when anti-VGCC antibodies are negative, to improve diagnostic accuracy.

Limitations:

• The study is based on a single case, limiting generalizability and necessitating further research to validate findings.
• Long-term outcomes and broader implications require further investigation to establish the reliability of anti-SOX1 as a diagnostic tool.

Conclusion:

The case highlights the importance of recognizing atypical presentations of LEMS and the role of specific antibody testing in diagnosing associated malignancies, which could lead to improved patient outcomes.