Expanding the spectrum of SOX1-antibodies in neuropathy: the coexistence of anti-SOX1 and Guillain-Barré syndrome—a case report

Background and aims: Antibodies against SOX1 (or anti-glial nuclear antibody, AGNA) are partially characterized onconeural antibodies, firstly described in association with small cell lung cancer (SCLC). Lambert-Eaton myasthenic syndrome is the most frequent paraneoplastic syndrome (PNS) found in patients with anti-SOX1-antibody positivity. Other associations are chronic axonal polyneuropathy, paraneoplastic limbic encephalitis, and paraneoplastic cerebellar degeneration. Methods: We describe a case of Guillain-Barré syndrome (GBS) with classical demyelinating phenotype associated with a positivity for anti-SOX1-antibodies. Results: A therapy with intravenous immunoglobulin led to progressive clinical improvement. After 12 months, clinical and neurophysiological pictures showed complete recovery. A thorough paraneoplastic screening was negative for underlying tumors. Conclusions: This is the first case of GBS associated with anti-SOX1-antibodies described in literature. Although the concept of paraneoplastic GBS is controversial, different cases have been reported and GBS is considered a non-classical paraneoplastic syndrome. Our case expands the anti-SOX1-antibody clinical spectrum with relevant implications for the clinical practice.