Miller Fisher Syndrome With Guillain-Barré Syndrome Overlap in a 20-Month-Old Girl: A Case Report.

Miller Fisher syndrome (MFS) is an uncommon variant of Guillain-Barré syndrome (GBS) classically characterized by ophthalmoplegia, ataxia, and areflexia. Overlap forms with GBS are rare in early childhood and may be difficult to recognize, particularly in toddlers in whom neurological examination is limited. We report the case of a 20-month-old girl who presented with a seven-day history of progressive gait disturbance, repeated falls, refusal to walk, and convergent strabismus. Neurological examination showed severe axial ataxia, inability to sit or stand without support, generalized areflexia, symmetrical limb weakness, and right abducens nerve palsy. Brain and spinal magnetic resonance imaging (MRI) were normal. Cerebrospinal fluid (CSF) analysis showed mild albuminocytologic dissociation. Electroneuromyography demonstrated an acute motor-predominant polyradiculoneuropathy with preserved sensory responses. Anti-ganglioside antibody testing was positive for anti-ganglioside GQ1b (anti-GQ1b) and anti-ganglioside GT1a (anti-GT1a) immunoglobulin G (IgG) antibodies, supporting a diagnosis within the anti-GQ1b antibody syndrome spectrum. Campylobacter jejuni serology was positive despite the absence of preceding gastrointestinal symptoms, suggesting a possible antecedent exposure rather than a confirmed active infection. The diagnosis of MFS with GBS overlap was retained. The patient was treated with intravenous immunoglobulin at a total dose of 2 g/kg, with close respiratory, bulbar, and autonomic monitoring and early rehabilitation. The outcome was favorable, with recovery of independent walking at one month and complete neurological recovery at six months. This case highlights the importance of considering MFS with GBS overlap in very young children presenting with acute gait disturbance and ocular motor signs.