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

Abstract

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.

Beyond Monoclonal Gammopathy of Undetermined Significance, Clinical Spectrum of Immunoglobulin M Gammopathy: A Case Series with Focus on the Diagnostic and Management Challenges

“…Similar to Bing–Neel syndrome, anti-MAG neuropathy may be treated with rituximab and/or bendamustine. When treated with rituximab monotherapy in a multicenter study, 44% of patients with anti-MAG secondary to WM saw overall improvement, with one case reporting significant improvement in compound muscle action potential in nerve conduction studies [ 34 , 35 ]. In one case diagnosed with both anti-MAG neuropathy and Bing–Neel syndrome, bendamustine monotherapy resolved sensory disturbance and weakness, improvement in nerve conduction studies, and normalized serum IgM levels [ 36 ].…”

Monoclonal Gammopathy–Associated Peripheral Neuropathy: Diagnosis and Management

“…55–58 These studies suggested a limited beneficial effect in some patients. Case reports have shown decreased IgM levels in IgM monoclonal gammopathy associated neuropathy and improvement of neuropathy in cases of anti-myelin-associated glycoprotein (MAG)/sulfated glucoronyl paragloboside (SGPG) associated Waldenström macroglobulinemia with rituximab treatment 56,58 . There have also been case reports of a neuropathy flare in WM following rituximab therapy.…”