To describe a rare case of tumefactive demyelination lesions in a patient with paraneoplastic neuromyelitis optica.

Tumefactive demyelination, rare lesions mimicking tumors, is observed in inflammatory disorders like multiple sclerosis. Few cases have been associated with neuromyelitis optica (NMO), an autoimmune inflammatory disorder of the central nervous system characterized by antibodies against the aquaporin-4 channel (AQP4). NMO affects the optic nerves, spinal cord, and brain.  Here, we present a unique case of tumefactive demyelinating lesions in an AQP4 antibody-positive NMO associated with renal cell carcinoma.

A 64-year-old male with PMH of HTN, CAD (s/p stent placement), and renal cell carcinoma presented to an outside hospital with left upper extremity and central facial paresis a month ago. Brain MRI revealed a right parietal mass that was biopsied, histology did not show evidence of malignancy but showed foamy macrophages suggesting demyelination. Patient was discharged on steroids; however, he was readmitted multiple time in the following weeks due to episodes of confusion, agitation, and a left hemibody focal tonic-clonic seizure. He was discharged on two antiseizure medications, with no further episodes. However, symptoms worsened, including left lower extremity paresis and a fall, prompting admission to our hospital. CT head showed a right parietal hyperdense lesion, MRI revealed two enhancing masses on the right hemisphere with vasogenic edema. MR spectroscopy without evidence of glioma. CSF showed elevated protein without oligoclonal bands or elevated IgG index. CT chest/abdomen/pelvis revealed a left renal mass. EEG showed right hemisphere slowing. Serum AQP4 antibodies were positive. Treatment with IV methylprednisolone followed by plasmapheresis and physical therapy resulted in significant symptom improvement, enabling ambulation.

NMO may present with tumefactive lesions, and its occurrence in older patients with an atypical presentation should raise suspicion for a paraneoplastic process. Our patient's case, had an unusual association with renal cell carcinoma.