Objective: To report a case of monoclonal gammopathy of undetermined significance (MGUS) with muscle atrophy as the first symptom and review the related literatures.

Methods: A case of MGUS with muscle atrophy as the first symptom was reported, and related publications were reviewedto discuss the diagnosis and treatment of MGUS with peripheral neuropathy.

Results: A 58-year-old man was admitted to the hospital with "left lower limb atrophy accompanied with upper limb numbness for more than 2 years". He had the clinical course of chronic onset and progressive aggravation. Physical examination revealed limb muscle atrophy, paresthesia, and non-elicitable bilateral tendon reflexes. Romberg sign was tested positive, and the tandem gait cannot be completed. Peripheral nerve damage was confirmed by electromyography, M protein and lgM-k type bands were found positive inimmunofixation electrophoresis analysis, In addition, anti-GM2 antibody lgM(+)anti-sulfatides antibody lgM (+)and anti-MAG antibody lgM (+) in serum as well asanti-GD1b lgM (+) in cerebrospinal fuid were found positive. The patient was diagnosedas lgM-MGUS according to medical history, physical examination and other auxiliary examinations. After maintainin glow-dose steroids application to inhibit autoimmunity,plasma exchange to remove pathogenic IgM protein, together with symptomatic support,his symptoms improved and was later discharged from hospital. The patient's condition did not develop after 1 year on follow-up visit.

Conclusion: Routine screening with blood immunofixation electrophoresis is required for patients with peripheral neuropathy, and careful differentiation from other diseases is necessary. The diagnosis and treatment of MGUS require multidisciplinary collaboration between neurology,radiology, hematology, and pathology department. Early detection accurate assessment and long-term follow-up are beneficial for improving patients'prognosis.