Waldenström Macroglobulinemia-Associated Peripheral Neuropathy in the Brachial Plexus With Bing-Neel Syndrome Diagnosed Through Repeated Cerebrospinal Tests

In Waldenström macroglobulinemia (WM), confirming the presence of Bing-Neel syndrome (BNS) is important because drugs that penetrate the central nervous system (CNS) must be selected. We report the case of a 75-year-old man for whom tirabrutinib, a second-generation Bruton's tyrosine kinase inhibitor (BTKi), was useful in treating WM-associated peripheral neuropathy (PN) with BNS. Numbness and muscle weakness in the fingers occurred three years after the initial treatment of WM. WM-associated PN due to demyelinating disease was diagnosed based on the results of a nerve conduction study and magnetic resonance imaging showing bilateral symmetric swelling of the brachial plexus. The cerebrospinal fluid (CSF) cytology results were initially negative; however, the CSF test was repeated because of extremely high protein levels (984 mg/dL) and slightly elevated leukocyte counts (14/µL). The second test revealed abnormal lymphoplasmacytic cells (189/µL), indicating BNS. Rituximab and high-dose methotrexate-containing chemotherapy were administered. Despite the subsequent negative CSF cytology results, his neurological symptoms persisted but subsided soon after the initiation of tirabrutinib. The therapeutic effects of tirabrutinib persisted for 25 months. This case suggested that a careful search for concurrent BNS is important when lesions are close to the CNS or when atypical CSF findings are obtained in patients with WM-associated PN, especially when BTKi options are available.

Bing-Neel Syndrome: An Initial Manifestation of Waldenstrom Macroglobulinemia

Waldenstrom macroglobulinemia (WM) is a low-grade B-cell lymphoma characterized by bone marrow infiltration by monoclonal lymphoplasmacytic cells plus an IgM monoclonal gammopathy. Bing-Neel syndrome (BNS) is a rare manifestation of WM where malignant lymphoplasmacytic cells infiltrate the central nervous system (CNS). Though only present in 0.8% of WM cases, it is likely underdiagnosed and may present before or during WM treatment. Here, we present a case of BNS as an initial sign of WM. A 75-year-old male presented with confusion, gait instability, and expressive aphasia. MRI demonstrated a 5.5-cm mass in the right frontal lobe, crossing midline. Brain biopsy showed CNS lymphoma and later tested positive for the MYD88L265P mutation suggesting WM (as is a mutation in 90-95% WM patients). Indeed, quantitative serum immunoglobulins showed elevated IgM. Initial treatment for WM was started with rituximab, methylprednisolone, carfilzomib, and ibrutinib. MRI two months after initiation showed good response, and the patient was transitioned to ibrutinib monotherapy. Surveillance MRI one year later showed patchy right frontal lobe enhancement indicating disease progression, and therefore the patient was placed back on his initial treatment regimen. However, ibrutinib later had to be held due to thrombocytopenia. Two months after re-starting chemotherapy, he presented with bizarre behavior, and MRI showed extensive disease progression. He was then transitioned to palliative chemotherapy with high-dose methotrexate and rituximab. He has responded well to this regimen, and MRI two years after diagnosis showed no recurrent disease. BNS is a rare but easily missed manifestation of WM. As per the recent National Comprehensive Cancer Network (NCCN) guidelines and the 8th International Workshop on WM (IWWM-8), no standardized diagnostic or management guidelines for BNS is available. Direct brain biopsy is the gold standard for diagnosis. Due to its low incidence, rarity, and limited prospective trial, there is a lack of a clear standard of care therapy. Specific treatment regimen depends on the patient factors and treatment tolerability. IWWM-8 suggests the use of a variety of cytotoxic chemotherapies or ibrutinib. A high-quality meta-analysis of existing reports is critical to characterize the diagnostic features and optimal treatment for BNS. The prognosis of BNS remains unclear, with an estimated three- and five-year survival rate at 59% and 71%, respectively. BNS is an infrequent complication of WM. Clinicians should suspect BNS with persistent, unexplained neurologic symptoms in WM.