Miller-Fisher Syndrome: Are Anti-GAD Antibodies Implicated in Its Pathophysiology?

Miller-Fisher syndrome (MFS) is considered as a variant of the Guillain-Barre syndrome (GBS) and its characteristic clinical features are ophthalmoplegia, ataxia, and areflexia. Typically, it is associated with anti-GQ1b antibodies; however, a significant percentage (>10%) of these patients are seronegative. Here, we report a 67-year-old female patient who presented with the typical clinical features of MFS. Workup revealed antibodies against glutamic acid decarboxylase (GAD) in relatively high titers while GQ1b antibodies were negative. Neurological improvement was observed after intravenous gamma globulin and follow-up examinations showed a continuous clinical amelioration with simultaneous decline of anti-GAD levels which finally returned to normal values. This case indicates that anti-GAD antibodies may be associated with a broader clinical spectrum and future studies in GQ1b-seronegative patients could determine ultimately their clinical and pathogenetic significance in this syndrome.