From Indolent Neuropathy to Aggressive Primary Neurolymphoma: Evolution of a Misleading Dysimmune Phenotype

Importance Primary neurolymphomatosis is a rare presentation of non-Hodgkin lymphoma characterised by initial peripheral nervous system involvement without systemic disease, frequently resulting in delayed diagnosis. Observations A 56-year-old man presented with a 5-year history of asymmetric progressive radiculoplexoneuropathy, initially treated with immunotherapy for presumed vasculitic neuropathy, with apparent disease stability for 4.5 years before rapid deterioration over the ensuing 6 months. Examination revealed asymmetric limb weakness of lower and then upper limbs, areflexia, distal sensory loss and cranial nerve palsies. Magnetic resonance imaging demonstrated diffuse thickening and enhancement of the brachial and lumbosacral plexuses and cauda equina. Fluorodeoxyglucose positron emission tomography-computed tomography (FDG PET-CT) showed hypermetabolic lesions involving the left sciatic nerve and cauda equina without systemic disease. Cerebrospinal fluid cytology and flow cytometry confirmed high-grade B-cell lymphoma. High-dose methotrexate–based combination chemotherapy achieved clinical remission at 14-month follow-up. Conclusions and Relevance: Chronic atypical radiculoplexoneuropathy with accelerated progression should prompt consideration of neurolymphomatosis to facilitate early diagnosis and improved outcomes.