A Case of Miller−Fisher Overlap Syndrome With Positive Anti‐GM4 Antibody and Atypical Symptoms

Background Miller−Fisher syndrome (MFS) is a recognized clinical variant of Guillain−Barré syndrome (GBS), characterized by the classic triad of ophthalmoplegia, ataxia, and areflexia. When accompanied by additional symptoms such as bulbar palsy, limb weakness, or lethargy, it is termed MFS overlap syndrome. Case Presentation This report describes a male patient diagnosed with MFS overlap syndrome, presenting with ophthalmoplegia, ataxia, bulbar palsy, numbness in both arms, positive GM4 IgG antibodies, a persistent, intractable headache, and a delayed onset of left‐sided peripheral facial palsy. The patient had a preceding suspected case of chlamydial pneumonia before symptom onset, and his condition improved significantly following treatment with intravenous immunoglobulin. Conclusion This case suggests that chlamydial pneumonia might predispose individuals to GBS. Patients with MFS/pharyngeal‐cervical‐brachial (PCB) overlap syndrome may exhibit atypical symptoms, including persistent, intractable headaches, and delayed peripheral facial paralysis. Atypical symptoms should not delay the diagnosis and treatment of GBS once other conditions have been adequately excluded. The presence of anti‐GM4 antibodies, often found alongside other anti‐ganglioside antibodies, may serve as a critical immunological factor in MFS/PCB overlap syndrome.