We report a 7-month-old female infant with 
Miller Fisher Syndrome (MFS), presenting with external 
ophthalmoplegia, blepharoptosis, ataxia, and loss of deep 
tendon reflexes. We treated the patient with high-dose 
immunoglobulin therapy (400 mg/kg/day, 5 days), which 
yielded favorable recovery. Serum anti-Cytomegalovirus 
(CMV) IgM antibody was positive in the early stage of the 
illness; therefore, association with CMV infection was 
suspected. Serum tests for antibodies to gangliosides, 
including anti-GQ1b immunoglobulin G, were negative. 
Tachycardia and increased sweating, signs of autonomic 
dysfunction, were observed during the clinical course. 
Magnetic resonance imaging revealed enhancement of the 
cauda equina on day 13 of illness; however, this 
enhancement was no longer seen 4 months later. Miller 
Fisher Syndrome is thought to be a variant of the acute 
inflammatory polyneuropathies, such as Guillain-Barre 
Syndrome (GBS). GBS occurs widely in infants through 
old adults, but infantile MFS is rare, and to the best of our 
knowledge, our case might be the youngest reported case 
in the literature.