[Miller-Fisher syndrome associated with monoclonal IgG lambda antibodies against ganglioside GQ1b]

We report a case of a 68-year-old man with classical triad, ophthalmoplegia, ataxia and areflexia in uncommon context. Our patient presented initial symptoms during radiation therapy for prostate cancer. After elimination of brainstem stroke and carcinomatous meningitidis by his general physician, he was referred with a provisional diagnosis of Miller-Fisher syndrome (MFS). The main characteristics of this case of MFS were uncommon: antecedent illness of urinary tract infections by Pseudomonas aeruginosa, presence of high titres of IgG antibodies directed against Mycoplasma pneumoniae, CSF pleocytosis and intrathecal IgG synthesis, serum and CSF monoclonal IgG in a monoclonal gammopathy of undetermined significance (MGUS). The serum and CSF immunological marker of MFS was a monoclonal IgG antibody targeting the ganglioside GQ1b with abundant expression on oculomotor nerves.