Objective: To report the clinical data of a patient who developed Miller-Fisher syndrome (MFS), the variant type of Guillain-Barré syndrome (GBS) after the administration of adalimumab, which aims to provide novel evidence of the association between TNF-α inhibitor and GBS.

Methods: We reported a case of MFS in a Crohn's disease patient following adalimumab administration. The clinical manifestations, auxiliary examinations, radiological scans, and diagnostic and treatment procedures were stated. Furthermore, the possible pathogenesis was assessed by reviewing the relevant references.

Results: A male patient aged 32 years old was diagnosed as Crohn 's disease three years ago. He was treated with infliximab for three years before switching to adalimumab for over four months. Ten days after his last dose of adalimumab, he complained of " double visions for 6 days" and was admitted to the hospital. On examination, there was limited movement in both eyes, and no abnormality was seen on brain MRI scanning with or without enhancement. The autoantibodies (anti-GT1a IgG antibody and anti-GQ1b IgG antibody) were positive in his blood test. He was diagnosed as MFS, which is a variant type of GBS. After discontinuing adalimumab, he was treated with intravenous immunoglobin, vitamin B₁₂, and vitamin B₁. His symptoms improved and he was discharged.

Conclusion:GBS can be caused by adalimumab, but the mechanism should be further investigated. Clinically, more attention should be paid to the possible increased risk of developing peripheral neuropathies when monoclonal antibody therapy is applied.