Cytomegalovirus-Associated Parainfectious Miller Fisher Syndrome Without Anti-GQ1b Antibodies: A Case Report.

Miller Fisher Syndrome (MFS) is a rare neurological disorder characterized by ataxia, areflexia, and ophthalmoplegia. It is considered a variant of Guillain-Barré syndrome (GBS). Infections frequently precede the onset of MFS. A 44-year-old patient was referred to our Neurology Department due to rapidly progressive bilateral limb ataxia, areflexia, and external ophthalmoplegia following acute tonsillitis with fever and oral mucosal lesions. Initial extensive diagnostic work-up, including immunoglobulin M (IgM) serum antibodies against cytomegalovirus (CMV), was negative. However, due to clinical suspicion, anti-CMV IgM was tested again and subsequently found to be positive. Interestingly, antibodies against Q1B ganglioside, which are specific for MFS, were also negative. Our patient gradually improved after intravenous immunoglobulin administration and symptomatic treatment. No underlying cause of immunocompromise was identified. This case underscores the importance of persistent testing for CMV antibodies in immunocompetent patients, even in rare cases of GBS like MFS, to ensure accurate diagnosis and optimize treatment plans.