Paraneoplastic cerebellar degeneration combined with Lambert-Eaton myasthenia gravis syndrome in a patient positive for SOX1 antibody

Abstract

A paraneoplastic syndrome (PNS) is a complex condition that worsens the quality of life of patients. It presents diverse clinical manifestations and can be challenging to diagnose. The role of the SOX1 antibody in PNS has been gaining attention, but clinicians frequently lack an understanding of PNS cases with positive antibody results and complex symptoms. This lack of understanding can lead to misdiagnosis and missed diagnoses. In this report, we present a typical case to highlight the importance of considering PNS when patients present with cerebellar lesions, symptoms resembling Lambert-Eaton myasthenic syndrome (LEMS), signs of peripheral nerve injury, or subclinical evidence. Recognizing these indicators of PNS is crucial for improving early diagnosis and patient prognosis. By sharing this case, our goal is to increase awareness of these unique PNS cases and provide insight for diagnosis and treatment.

Keywords: Lambert-Eaton myasthenia gravis syndrome; Paraneoplastic syndromes; SOX1 antibody; paraneoplastic cerebellar degeneration; small cell lung cancer.

Figure 1

Cranial MRI findings. Mild demyelinating changes in the white matter of the brain. A-D. DWI. E-H. FLAIR.

Figure 2

Repetitive electrical nerve stimulation (RNS). A-H. Low-frequency decreasing and High-frequency increasing in the bilateral ulnar nerve. I, J. Low-frequency decreasing in the right axillary nerve.

Figure 3

Chest CT findings. A. Space-occupying lesion in the right upper lung (2021. 6. 28). B. Disappearance of right upper lung lesion (2022. 6. 5).

Figure 4

Representative immunostaining of cancer biomarkers in lung tissue. A. Ki67-positive. B. TTF1-positive. C. SYN-positive. D. LCA-positive. E. CD56-positive. F. CK7-positive. Original magnification, 100×.