Severe Worsening of Neuropathy Associated With Antibodies Against Myelin-Associated Glycoprotein by Rituximab Resembling Chronic Inflammatory Demyelinating Polyneuropathy.

The presence of antibodies against myelin-associated glycoprotein (anti-MAG) is typically associated with distal acquired demyelinating symmetric neuropathy (DADS), usually presenting with slowly evolving sensory more than motor distal predominant polyneuropathy. On electrodiagnostic testing, DADS tends to show findings indicating distal predominant demyelination. Despite being a predominantly demyelinating neuropathy, DADS is resistant to multiple immunotherapies. Rituximab has been used as a successful treatment in a portion of patients with DADS, but rare cases of worsening of anti-MAG neuropathy have also been previously described. Here we describe a male patient with DADS who possessed high-titer anti-MAG antibodies. However, immediately following two doses of rituximab, he demonstrated a significant deterioration with acute proximal limb weakness and positive response to treatment of corticosteroid and intravenous immunoglobulin, resembling chronic inflammatory demyelinating polyneuropathy (CIDP).