Miller Fisher syndrome is a variant of Guillain-Barre syndrome characterized by 
the classic triad of ophthalmoplegia, ataxia, and areflexia. Pupillary 
involvement is common in MFS and has been reported in 35-42% of MFS patients. 
Although case reports have discussed isolated ophthalmoplegia as a presentation 
of MFS, anisocoria and rapid fluctuation of pupillary diameter have not been 
reported in anti-GQ1b antibody positive individuals. Here we describe an 
individual who presented with diplopia and was found to have progressive 
internal and external ophthalmoplegia with frequent fluctuations in pupillary 
diameter and anisocoria. These exam findings are not commonly described even in 
atypical presentations of MFS. The onset of symptoms was preceded by an upper 
respiratory infection but no gastrointestinal symptoms. Imaging and CSF studies 
were unremarkable; however serum levels of immunoglobulin G anti-GQ1b antibody 
and anti-GAD antibody were elevated confirming the diagnosis of MFS. The patient 
was treated with IVIG and intravenous steroids with mild resolution of external 
ophthalmoplegia. He did not go on to develop more typical features of MFS such 
as ataxia or areflexia. This demonstrates that isolated external and internal 
ophthalmoparesis with rapidly fluctuating pupillary diameter and associated 
anisocoria can be the sole manifestation of atypical MFS.