Neurosarcoidosis Mimicking the Recurrence of Malignant Lymphoma

A 67-year-old woman with a recurrent history of malignant lymphoma (ML) presented with muscle weakness and paresthesia of the fingertips and feet. Due to the elevated level of serum soluble interleukin-2 receptor and increased ¹⁸F-fluorodeoxyglucose uptake in a mediastinal lymph node, neurolymphomatosis was initially suspected. Neurological and electrophysiological examinations were consistent with mononeuropathy multiplex. A diagnosis of neurosarcoidosis was made based on the presence of noncaseating epithelioid granulomas in the mediastinal lymph node, along with the presence of the uveitis, cardiac inflammation, and mononeuropathy multiplex. She was treated with glucocorticoids and azathioprine, and her symptoms disappeared. Sarcoidosis following ML is rare, and since biopsy of nervous systems is often improbable, differentiating neurosarcoidosis and neurolymphomatosis can be difficult as their clinical symptoms can be similar. Clinicians should consider systemic pathological investigations based on ¹⁸F-fluorodeoxyglucose positron emission tomography examination in addition to comprehensive evaluation to accurately diagnose neurosarcoidosis.