Diffuse large B-cell lymphoma presenting with anti-MAG/SGPG IgM gammopathy and neurolymphomatosis at onset

Anti-MAG/SGPG antibody is an IgM antibody against myelin-associated glycoprotein and sulfate-3-glucuronyl paragloboside, which constitute the myelin sheath, and peripheral neuropathy associated with this antibody causes symptoms such as sensory disturbances and ataxia. Anti-MAG/SGPG antibodies are known to be associated with IgM monoclonal gammopathy derived from plasma cell tumors. Chemotherapy with rituximab has been shown to yield neurological improvement in patients with peripheral neuropathy positive for anti-MAG/SGPG antibodies. Here we report a very rare case of diffuse large B-cell lymphoma presenting with neurolymphomatosis along with sensorimotor neuropathy associated with anti-MAG/SGPG antibody-positive IgM monoclonal gammopathy.