Successful treatment with tirabrutinib for relapsed lymphoplasmacytic lymphoma complicated by Bing-Neel syndrome.

A 53-year-old woman was diagnosed with lymphoplasmacytic lymphoma (LPL)/Waldenström's macroglobulinemia (WM) in 2008. Six courses of R-COP (rituximab, cyclophosphamide, vincristine, and prednisolone) resulted in complete remission, but LPL/WM relapsed in 2015. After six courses of R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisolone), the M-peak disappeared, but the patient presented with muscle weakness and sensory disturbance in the lower extremities. No lesions were apparent in the brain parenchyma, but T2-weighted magnetic resonance imaging (MRI) showed a signal-hyperintense area with contrast enhancement in the spinal cord at the C2-4 and Th2-3 levels, and cerebrospinal fluid (CSF) examination showed only a few mononuclear cells. In 2020, the patient started to require walking assistance, and MRI findings worsened. Neurologically, lower limb muscle strength was reduced (manual muscle test score 3), and sensations of touch and pain were about 30% of normal. Vibratory sensation was absent at the knees and medial malleoli, accompanied by dysuria due to neurogenic bladder. CSF cell count was 15/μl (all mononuclear cells). Bing-Neel syndrome (BNS) was diagnosed and tirabrutinib was started. Within 2 months of treatment, lower extremity muscle strength had normalized and MRI findings had improved. Tirabrutinib may offer a promising therapeutic option for BNS.