Beneficial Effect of Bendamustine in a Patient with Anti-MAG/SGPG Neuropathy and Bing-Neel Syndrome Associated with Waldenström Macroglobulinemia: A Case Report

: A 71-year-old man with Waldenstrom macroglobulinemia (WM) presented with a slowly progressive sensory disturbance and mild weakness predominantly affecting the distal portion of the limbs over the course of 6 months. Cervical magnetic resonance imaging (MRI) showed a long hyperintense lesion at the C1-C4 level. Nerve conduction studies (NCS) revealed prolongation of distal latency, slowed conduction velocity, and conduction block. His serum IgM level was increased, and he was positive for anti-myelin-associated glycoprotein (MAG) and anti-sulfoglucuronyl paragloboside (SGPG) IgM antibodies. Based on the presence of anti-MAG/SGPG antibodies and a single atypical cell with lymphoplasmacytic character in the cerebral spinal fluid, he was diagnosed as having anti-MAG/SGPG neuropathy and Bing-Neel syndrome (BNS) associated with WM. Following 6 cycles of bendamustine monotherapy, the patient's neurological impairment improved; and the serum IgM level became normalized. Furthermore, NCS findings indicated improvement; and the hyperintense lesion on MRI had almost completely disappeared. The present findings suggest that bendamustine monotherapy is effective not only for WM but also for its associated MAG/SGPG neuropathy and BNS.