[Successful treatment of Guillain-Barré syndrome-like acute inflammatory demyelinating polyneuropathy caused by pembrolizumab with a combination of corticosteroid and immunoglobulins: a case report].

A 74-year-old man, who received pembrolizumab for the treatment for non-small cell lung cancer, developed quadriparesis 10 days after the first course of treatment accompanied by gait disturbance. Dysesthesia was observed in the distal extremities, and tendon reflexes were absent. Neurological examination and peripheral nerve conduction study supported the diagnosis of Guillain-Barré syndrome-like acute inflammatory demyelinating polyneuropathy caused by pembrolizumab. The administration of pembrolizumab was discontinued. Moreover, he was initially treated with intravenous immunoglobulin therapy, followed by intravenous methylprednisolone therapy and oral prednisolone. The limb weakness improved to a degree that he could walk alone on discharge. Pembrolizumab, which is an immune checkpoint inhibitor with a high anti-tumor effect, is reported to cause various adverse events. However, neuromuscular complications following cancer treatment with immune checkpoint inhibitors are relatively rare. Treatment with corticosteroids is considered to be effective for treating immune-related adverse events. Corticosteroids were effective in treating peripheral neuropathy caused by immune checkpoint inhibitors in this patient. Thorough treatment should be considered with a combination of corticosteroids and immunoglobulin therapy, in addition to discontinuation of immune checkpoint inhibitors, for this rare entity, which differs from that for idiopathic Guillain-Barré syndrome.