Antibody Positive Miller-Fisher Syndrome and Acute Motor Sensory Axonal Neuropathy With Respiratory Failure: A Rare Overlap.

Miller-Fisher syndrome (MFS), a rare variant of Guillain-Barré syndrome (GBS), is classically defined by ophthalmoplegia, ataxia, and areflexia and is strongly associated with anti-GQ1b antibodies. We report a 35-year-old man presenting with classical MFS features who rapidly deteriorated with progressive limb weakness and respiratory failure requiring mechanical ventilation. Cerebrospinal fluid analysis showed albuminocytologic dissociation, while nerve conduction studies were consistent with an axonal process. Serologic testing revealed positivity for both anti-GQ1b and anti-GD1a antibodies, confirming an overlap between MFS and acute motor sensory axonal neuropathy (AMSAN). The patient showed marked neurological recovery following intravenous immunoglobulin therapy and intensive supportive care. This case highlights a rare MFS-AMSAN overlap with respiratory failure and underscores the importance of early recognition, vigilant respiratory monitoring, and prompt immunotherapy in preventing morbidity and optimizing patient outcomes in rapidly progressive GBS-spectrum disorders.