Myasthenia gravis-like neuromuscular junction dysfunction in a patient with Miller-Fisher variant of Guillain–Barré syndrome

Miller-Fisher syndrome, a variant within the Guillain -Barré syndrome spectrum, may rarely present with myasthenia gravis (MG)- like features, creating diagnostic uncertainty. Although traditionally regarded as a peripheral neuropathy, transient neuromuscular junction (NMJ) transmission abnormalities have been described in anti-GQ1b spectrum disorders. A 52-year-old man presented with acute diplopia and ophthalmoplegia following an upper respiratory infection. Neurological examination revealed bilateral ophthalmoplegia and hyporeflexia without objective limb ataxia. Nerve conduction studies showed reduced tibial compound muscle action potential amplitudes and absent H-reflexes. Repetitive nerve stimulation demonstrated a modest decrement with partial post-exercise augmentation and recovery. Subsequently, the patient developed ptosis and dysphonia, which improved after symptomatic pyridostigmine therapy. Anti-GQ1b and MG-related antibodies and cerebrospinal fluid (CSF) analysis were unavailable. The clinical course was most consistent with transient NMJ dysfunction within the anti-GQ1b spectrum, but the coexistence of MG cannot be definitively excluded. Awareness of this potential overlap is crucial to avoid misclassification and guide management.