Coexisting Myasthenia Gravis and Demyelinating Polyneuropathy: A Case Report and Literature Review

Introduction Myasthenia gravis (MG) and demyelinating polyneuropathy affect different components of the peripheral motor system but may both contribute to limb weakness. We report a patient with MG and coexisting demyelinating polyneuropathy and review previously reported MG‐CIDP cases. Methods We described a 68‐year‐old woman with AChR antibody‐positive MG and coexisting demyelinating polyneuropathy and conducted a systematic review in accordance with the PRISMA guidelines. Clinical characteristics, laboratory findings, electrophysiological results, treatments, and outcomes were analyzed. Results The patient presented with fluctuating ocular symptoms and chronic progressive limb weakness. She tested positive for anti‐AChR antibodies. Archived electrophysiological studies showed a demyelinating polyneuropathy pattern, and cerebrospinal fluid analysis revealed albuminocytological dissociation. Marked clinical improvement was achieved with pyridostigmine, intravenous immunoglobulin, and corticosteroids. Twelve previously reported MG‐CIDP cases were analyzed separately. Of these, 50.0% were female and 83.3% were middle‐aged or elderly. MG and CIDP occurred simultaneously in 58.3%, MG preceded CIDP in 33.3%, and CIDP preceded MG in 8.3%. Limb, bulbar, and ocular involvement occurred in 83.3%, 75.0%, and 66.7%, respectively. Nerve conduction abnormalities were present in all patients; RNS and anti‐AChR antibodies were positive in 83.3%. Thymoma occurred in 33.3%. Corticosteroids and intravenous immunoglobulin were each used in 83.3%, and all patients improved. Conclusion Coexisting demyelinating polyneuropathy should be considered in MG patients with persistent limb weakness, generalized areflexia, or nerve conduction abnormalities not fully explained by neuromuscular junction dysfunction.