Delayed apperance of anti–myelin‐associated glycoprotein antibodies in a patient with chronic demyelinating polyneuropathy

A patient who had a polyneuropathy compatible with a chronic inflammatory demyelinating polyneuropathy and was initially negative for anti-myelin-associated glycoprotein (MAG) antibodies developed a double monoclonal gammopathy, IgM kappa and IgM lambda, two years after the diagnosis. The IgM kappa, but not the IgM lambda, exhibited strong anti-MAG antibody activity. The late appearance of the anti-MAG immunoreactivity suggests that in patients with an initial diagnosis of chronic inflammatory demyelinating polyneuropathy, the search for anti-MAG antibodies should be repeated during the course of the neuropathy.