Rituximab Improves Subclinical Temporal Dispersion of Distal Compound Muscle Action Potential in Anti-MAG/SGPG Neuropathy Associated with Waldenström Macroglobulinemia: A Case Report

Patients with anti-myelin-associated glycoprotein (MAG)/sulfated glucuronyl paragloboside (SGPG) neuropathy associated with Waldenström macroglobulinemia show demyelinating neuropathy, but the temporal dispersion of distal compound muscle action potential (CMAP) in motor nerve conduction studies (NCS), which represents heterogeneous demyelination at the motor nerve terminal, is rare. We report on a 70-year-old man with anti-MAG/SGPG neuropathy associated with Waldenström macroglobulinemia; he had a 2-year history of mild dysesthesia of the foot sole without any motor symptoms. He showed marked temporal dispersion of distal CMAP in the tibial nerve with other demyelinating findings in the NCS. The temporal dispersion of distal CMAP in the tibial nerve improved significantly, and motor function was again normal 1 year after rituximab monotherapy. The temporal dispersion of distal CMAP in anti-MAG/SGPG neuropathy is rare, but it could occur from an early stage when the patients show mild or no motor symptoms. Rituximab therapy before secondary axonal degeneration has great potential to reverse the effects of the demyelination including the temporal dispersion of distal CMAP, and to prevent the deterioration of neuropathy in anti-MAG/SGPG neuropathy.