Newly Developing IgM Anti‐ GD1a / GD1b Ganglioside IgM Monoclonal Gammopathy in a Patient With Chronic Inflammatory Demyelinating Polyradiculoneuropathy

ABSTRACT Background and Aims Chronic inflammatory demyelinating neuropathy (CIDP) is a rare, immune‐mediated neuropathy that is distinct from other immune‐mediated, paraneoplastic, and paraproteinemic neuropathies that may have overlapping clinical features. Identification of the specific diagnosis in each patient is important as each of these disorders has distinct pathophysiology and treatment response. Case Report Here, we present an atypical case of CIDP in which the patient developed an IgM monoclonal gammopathy with positive anti‐ganglioside antibodies over 20 years into his disease course. Interpretation Patients with CIDP may be predisposed to develop IgM autoantibodies or monoclonal gammopathies. If a patient with CIDP experiences clinical worsening while on maintenance therapy, it may be helpful to test for anti‐ganglioside antibodies and monoclonal gammopathies and reassess if alternative treatment would be useful.