{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,24]],"date-time":"2026-02-24T11:11:43Z","timestamp":1771931503519,"version":"3.50.1"},"reference-count":18,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,2,11]],"date-time":"2026-02-11T00:00:00Z","timestamp":1770768000000},"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. Immunol."],"abstract":"<jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>Morvan syndrome is a rare autoimmune disorder characterized by peripheral nerve hyperexcitability with autonomic and central nervous system involvement, most commonly associated with antibodies against contactin-associated protein-like 2 (CASPR2). Acute motor and sensory axonal neuropathy (AMSAN) is an axonal variant of Guillain\u2013Barr\u00e9 syndrome linked to anti-ganglioside antibodies and often manifests as severe limb weakness. Their concurrent presentation is unusual and raises the possibility of shared immune targets within peripheral nerve microdomains.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Case presentation<\/jats:title>\n                    <jats:p>A 70-year-old man presented with a relapsing course of progressive lower-limb weakness accompanied by widespread muscle twitching, severe insomnia with nocturnal hyperarousal, and refractory constipation. He had a prior episode diagnosed as AMSAN that improved after immunotherapy but relapsed four months after treatment was discontinued. Neurological examination demonstrated bilateral lower-limb weakness with reduced tendon reflexes. Moreover, electrophysiological studies confirmed diffuse multifocal peripheral nerve injury with superimposed peripheral nerve hyperexcitability. In addition, immunologic testing revealed serum anti-GM1 antibodies and anti-CASPR2 IgG in both serum and cerebrospinal fluid. Collectively, these findings supported a diagnosis of recurrent AMSAN coexisting with CASPR2-associated Morvan syndrome. Combined immunotherapy with corticosteroids and intravenous immunoglobulin, alongside symptomatic management, resulted in marked clinical improvement.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>This case report describes a rare overlap of relapsing AMSAN and Morvan syndrome. This antibody-defined coexistence is hypothesis-generating and may reflect synergistic immune injury involving nodal and paranodal regions. This case underscores the importance of recognizing overlapping phenotypes to guide diagnostic profiling and immunomodulatory therapy.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.3389\/fimmu.2026.1755001","type":"journal-article","created":{"date-parts":[[2026,2,11]],"date-time":"2026-02-11T07:09:55Z","timestamp":1770793795000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["A rare presentation of CASPR2-associated Morvan syndrome overlapping with GM1-positive AMSAN: a case report"],"prefix":"10.3389","volume":"17","author":[{"given":"Yajing","family":"Wu","sequence":"first","affiliation":[{"name":"Department of Neurology, Hebei Medical University","place":["Shijiazhuang, Hebei, China"]},{"name":"Department of Neurology, Hebei General Hospital","place":["Shijiazhuang, Hebei, 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