Bing-Neel syndrome: a rare neurological complication of Waldenström macroglobulinaemia.

Bing-Neel syndrome (BNS) is a very rare manifestation of Waldenström macroglobulinaemia (WM), in which lymphoplasmacytic cells invade the central nervous system. The clinical presentation includes symptoms of headaches, visual floaters, neuropathy, seizures and gait abnormalities. Here, we describe an elderly woman, who presented with complaints of visual floaters, progressive neuropathy and cognitive changes. Workup including a bone marrow biopsy confirmed the diagnosis of WM. Shortly afterwards, the patient experienced a seizure leading to hospitalisation, which revealed a right frontal lobe lesion on brain MRI. A biopsy of the lesion showed a small B cell lymphoma positive for an MYD88 mutation, confirming BNS. The patient was initially treated with ibrutinib, before transitioning to zanubrutinib. However, she developed disease progression necessitating radiotherapy with lenalidomide and rituximab maintenance therapy, which achieved remission. This case sheds light on the diagnosis and management of a very rare complication of a rare disease.