Discordant SOX-1 antibodies results in paraneoplastic Lambert-Eaton syndrome diagnosis by the clinical laboratory

• Published in: Clinical biochemistry Vol. 97; pp. 82 - 84
• Main Authors: Pozo-Giraldez, Adela, Rodríguez-Borja, Enrique, Diaz-Gimenez, Macarena, Carratala-Calvo, Arturo, Magro-Pose, Pablo, Perez-Griera, Jaume
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.11.2021
• Subjects: Aged; Antibodies - blood; Female; Humans; Lambert-Eaton Myasthenic Syndrome - blood; Lambert-Eaton Myasthenic Syndrome - diagnosis; Lambert-Eaton myasthenic syndrome. MeSH Unique ID: D015624; Paraneoplastic syndromes, Nervous system. MeSH Unique ID: D020361; Small cell lung carcinoma. MeSH Unique ID: D055752; SOX-1 antibodies; SOXB1 Transcription Factors - immunology; Lambert-Eaton myasthenic syndrome. MeSH Unique ID: D015624; Paraneoplastic syndromes, Nervous system. MeSH Unique ID: D020361; Small cell lung carcinoma. MeSH Unique ID: D055752; SOX-1 antibodies
• ISSN: 0009-9120; 1873-2933; 1873-2933
• DOI: 10.1016/j.clinbiochem.2021.08.004

Anti-Sry-like high mobility group box 1 (anti SOX-1) proteins are rare onconeural antibodies associated with paraneoplastic Lambert-Eaton myasthenic syndrome (LEMS). Few patients with anti-SOX-1 antibodies and negative anti-glial nuclear antibody reactivity have been described to date. Our case involves a 72-year-old female patient with progressive girdle weakness, sensation of heaviness in the lower limbs, predominantly distal and associated with circulatory problems together with instability when walking, with a high suspicion of an autoimmune myopathic disorder. Immunoblot test for autoimmune myopathies antibodies detection were all negative. Onconeuronal antibodies were determined in serum by indirect immunofluorescence being negative as well. Given the high suspicion, we also checked for the presence of other antineuronal antibodies whose patterns are not visible by IIF. Onconeuronal antibodies by immunoblot for the following antibodies: Hu, Ri, Yo, Zic4, Tr, PCA-2, MA-TA, CV2, GAD65, Zic4, Titin, SOX1, Recoverin and Amp, revealed an unexpected clear band in SOX-1, which are highly suggestive of paraneoplastic LEMS. We hypothesize that discordant onconeuronal antibodies results were due to the fact that positivity in IIF is associated with other SOX-B group proteins (normally related to cases of non-paraneoplastic neuropathy), while negativity in IIF and subsequent confirmed presence of specific SOX1 antibody by immunoblot could indicate an underlying tumor.