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 Waldenström 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.