{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,9]],"date-time":"2026-07-09T05:15:14Z","timestamp":1783574114848,"version":"3.55.0"},"reference-count":29,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,7,9]],"date-time":"2026-07-09T00:00:00Z","timestamp":1783555200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Cell. Neurosci."],"abstract":"<jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>\n                      Paraneoplastic autoimmune encephalitis (PAE) is most commonly associated with small cell lung cancer (SCLC). Anti\u2013\n                      <jats:italic>\u03b3<\/jats:italic>\n                      -aminobutyric acid B receptor (GABABR) antibodies underlie a treatable limbic syndrome, whereas anti\u2013SRY-box transcription factor 1 (SOX1) antibodies serve as high-specificity onconeural biomarkers of SCLC-driven autoimmunity. The sequential emergence of these two antibodies during the longitudinal course of a single patient has rarely been documented.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Case presentation<\/jats:title>\n                    <jats:p>\n                      A 75-year-old man presented with episodic impaired consciousness, behavioural disturbance and rapid cognitive decline. Brain MRI showed bilateral hippocampal signal abnormalities. A cell-based assay (CBA) detected anti-GABABR antibodies at high titre in serum (1:3200) and cerebrospinal fluid (CSF; 1:1000), while a tissue-based assay (TBA) on rat brain confirmed a neuronal cell-surface staining pattern; the full paraneoplastic panel, including anti-SOX1, was negative, and initial tumour screening was unrevealing. A diagnosis of anti-GABABR encephalitis (initially regarded as non-paraneoplastic) was made and the patient improved with intravenous immunoglobulin (IVIG), high-dose corticosteroids and maintenance mycophenolate mofetil. During a refractory second relapse 5 months later, repeat CBA showed rising anti-GABA\n                      <jats:sub>B<\/jats:sub>\n                      R titres (serum 1:10,000; CSF 1:1000) and newly positive anti-SOX1 antibodies (serum 1:100; CSF 1:1); a previously occult right superior mediastinal mass radiologically compatible with SCLC was identified on repeat chest CT. The diagnosis was revised to anti-GABA\n                      <jats:sub>B<\/jats:sub>\n                      R\/anti-SOX1 dual-antibody PAE (probable PNS by 2021 PNS-Care criteria). The family declined biopsy, PET\/CT and antitumour therapy because of advanced age and frailty; repeated IVIG with continued immunosuppression achieved partial clinical stabilisation with persistent cognitive impairment.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>\n                      Apparently isolated anti-GABA\n                      <jats:sub>B<\/jats:sub>\n                      R encephalitis can evolve into dual anti-GABABR\/anti-SOX1 paraneoplastic disease, with the second antibody heralding an occult SCLC. Repeating both CBA-based and intracellular antibody panels at every clinical relapse, together with repeat thoracic imaging, is essential to avoid missing an evolving paraneoplastic aetiology.\n                    <\/jats:p>\n                  <\/jats:sec>","DOI":"10.3389\/fncel.2026.1816167","type":"journal-article","created":{"date-parts":[[2026,7,9]],"date-time":"2026-07-09T04:21:28Z","timestamp":1783570888000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Case Report: A case of paraneoplastic autoimmune encephalitis with concurrent anti-GABABR and anti-SOX1 antibody positivity"],"prefix":"10.3389","volume":"20","author":[{"given":"Feng","family":"Liu","sequence":"first","affiliation":[{"name":"Longhui People\u2019s Hospital","place":["Shaoyang, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ye-Han","family":"Jiang","sequence":"additional","affiliation":[{"name":"Longhui People\u2019s Hospital","place":["Shaoyang, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yu-Fang","family":"Hu","sequence":"additional","affiliation":[{"name":"Longhui People\u2019s Hospital","place":["Shaoyang, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jin-Guan","family":"Qin","sequence":"additional","affiliation":[{"name":"Longhui People\u2019s Hospital","place":["Shaoyang, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Guang-Sheng","family":"Liu","sequence":"additional","affiliation":[{"name":"Longhui People\u2019s Hospital","place":["Shaoyang, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2026,7,9]]},"reference":[{"key":"ref1","doi-asserted-by":"publisher","first-page":"1173484","DOI":"10.3389\/fimmu.2023.1173484","article-title":"Algorithm to improve the diagnosis of paraneoplastic neurological syndromes associated with SOX1 antibodies","volume":"14","author":"Arnaldos-P\u00e9rez","year":"2023","journal-title":"Front. 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