Glial Fibrillary Acidic Protein (GFAP) Autoimmunity in the Setting of Seropositive Rheumatoid Arthritis Treated With Etanercept.

Introduction: Glial fibrillary acidic protein (GFAP) immunoglobulin G is a recently discovered biomarker of an autoimmune central nervous system disorder characterized by a steroid-responsive meningoencephalomyelitis.
Case Report: A 63-year-old man with rheumatoid arthritis on etanercept presented with steroid-responsive subacute encephalopathy and foot drop. Brain and sural nerve biopsies demonstrated a T-cell perivascular infiltrate. Cerebrospinal fluid studies 18 months into the course of the illness demonstrated a GFAP antibody on mouse tissue immunofluorescence confirmed by cell-based assay. The patient was treated with steroids and cyclophosphamide leading to resolution of his symptoms.
Conclusion: This case expands on the previously reported cases of GFAP immunoglobulin G autoimmunity by describing an associated inflammatory large fiber peripheral neuropathy.