Treatment of Anti-Myelin-Associated Glycoprotein (MAG) Antibody Neuropathy Using Zanubrutinib in a Patient With Waldenström Macroglobulinemia: A Clinical Vignette

The objective of this paper is to report a case of anti-myelin-associated glycoprotein (anti-MAG) antibody neuropathy treated with zanubrutinib, offering insight into a potential therapeutic avenue for this challenging neurological disorder. A 65-year-old male initially presented with peripheral neuropathy in the lower distal extremities. Hematologic evaluation revealed an elevated M-spike of IgM and a high MAG antibody titer. His initial titer was measured at 1:102400 on February 28, 2023. These findings were consistent with the diagnosis of Waldenström macroglobulinemia (WM) with associated anti-MAG antibody neuropathy. The patient was started on rituximab and reported a slight improvement in symptoms. However, the patient felt the efficacy of rituximab diminished with each subsequent dose. Due to this, the patient was initiated on zanubrutinib. Close monitoring of clinical symptoms and laboratory parameters was conducted to assess treatment response and potential side effects. Following zanubrutinib therapy, the patient exhibited mild improvement in neuropathic symptoms, which have stabilized, although still present. Serologic examination demonstrated a decrease in anti-MAG-antibody titer at 1:25600 in the spring of 2023 and 1:51200 in November of 2023. Patient reports increased fatigue and musculoskeletal pain. This clinical vignette highlights the outcomes of zanubrutinib in the management of anti-MAG antibody neuropathy in a patient with WM. Further research and larger clinical trials are warranted to validate these findings and establish zanubrutinib as a viable therapeutic option for this rare and often challenging neurological disorder.