To present a unique case of glial fibrillary acidic protein (GFAP) astrocytopathy presenting with multifocal nervous system manifestations in the setting of parkinsonism and clear cell renal cell carcinoma (ccRCC).

GFAP astrocytopathy is an autoimmune disorder with meningoencephalitis and myelitis. Accompanying inflammatory polyneuropathy is rare and may be most responsive to high dose corticosteroids.

We present a 66-year-old male patient with a seven year parkinsonism history who presented with acutely progressive, diffuse extremity weakness and numbness. He developed areflexia and cerebral spinal fluid (CSF) analysis revealed >200 mg/dL protein with 4 white blood cells. Nerve conduction studies demonstrated a severe sensorimotor polyneuropathy with mixed demyelinating and axonal features. He was diagnosed with acute inflammatory demyelinating polyradiculoneuropathy (AIDP) and received 2 g/kg of IVIG and later 5 sessions of plasmapheresis without clinical improvement over two months.

He became encephalopathic with unremarkable magnetic resonance imaging of the brain. He developed generalized seizures and myoclonus treated with levetiracetam. CSF studies demonstrated GFAP autoantibodies. A neoplastic evaluation revealed a right renal lesion, confirmed as ccRCC by pathology. He had rapid improvement in mental status and strength after 7 days of methylprednisolone 1g/day. A prednisone taper continued over six weeks with subsequent transition to rituximab.

This patient with parkinsonism developed a mixed central and peripheral nervous system syndrome characterized by polyneuropathy and meningoencephalitis secondary to GFAP astrocytopathy with new ccRCC. The early predominating peripheral features (areflexia, electrodiagnostic neuropathy, albuminocytologic dissociation) led to diagnosis of AIDP with suboptimal immunotherapy for GFAP astrocytopathy. Central features (encephalopathy, seizures, myoclonus) consistent with astrocytopathy emerged later.

GFAP autoantibodies are associated with acute onset of movement disorders, but without known associations with parkinsonism. Previously documented cases of GFAP autoantibodies with ccRCC suggest a paraneoplastic etiology. The patient had a typical superior response to corticosteroids compared to IVIG or plasmapheresis.