Progressive Weakness in Lymphoma Remission: Neurolymphomatosis Masquerading as Chronic Inflammatory Demyelinating Polyradiculoneuropathy

Case Diagnosis: Neurolymphomatosis presenting as Chronic Inflammatory Demyelinating Polyradiculoneuropathy (CIDP) in a patient with Lymphoma in remission.

Case Description or Program Description: A 77-year-old male with diffuse large B-cell lymphoma in remission presented with subacute progressive bilateral hand weakness, numbness, and tingling. Initial examination revealed upper extremity weakness, hyperalgesia, and hyporeflexia. Electrodiagnostic studies (EDX) demonstrated conduction blocks and temporal dispersion, along with multifocal nerve enlargements on ultrasound. Initial evaluation met the 2021 European Academy of Neurology/Peripheral Nerve Society (EAN/PNS) criteria for possible CIDP. However, further workup revealed monoclonal B-cells in the cerebrospinal fluid and PET imaging showed widespread FDG-avid disease with bony involvement—establishing the diagnosis of neurolymphomatosis.

Setting: Outpatient electrodiagnostic clinic.

Assessment/Results: EDX demonstrated demyelinating features including bilaterally absent sural sensory studies and conduction block in the right median motor study, which is “weakly” supportive of demyelination according to the 2021 EAN/PNS CIDP criteria. A subsequent neuromuscular ultrasound revealed marked, focal nerve enlargements in non-entrapment sites, consistent with CIDP or another multifocal process. The history of lymphoma and somewhat unusual clinical and EDX profile prompted CSF cytology, which revealed mildly elevated protein (91.5 mg/dL) with lymphocytic pleocytosis. Flow cytometry detected a clonal B-cell population with increased cell size. PET scan confirmed widespread disease relapse.

Discussion (relevance): This case emphasizes that neurolymphomatosis can mimic CIDP clinically, electrodiagnostically, and sonographically. Both diseases involve multifocal peripheral nerve lesions with features of acquired demyelination and enlargements on imaging that make the distinction challenging. Even when initial findings suggest a more common diagnosis, maintaining clinical vigilance and pursuing comprehensive evaluation is crucial in patients with lymphoma history presenting with neurologic complaints.

Conclusions: When evaluating suspected CIDP in patients with a history of lymphoma, clinicians should consider neurolymphomatosis in the differential diagnosis. CSF flow cytometry and PET imaging are essential in such cases to aid in prompt diagnosis and improvement of treatment outcomes.