Bilateral Orbital Fat Hyperintensity in Early Glial Fibrillary Acidic Protein Astrocytopathy

OBJECTIVES: Glial fibrillary acidic protein (GFAP) astrocytopathy is an inflammatory autoimmune disease of the CNS that targets astrocytes. Although optic disc edema is a frequently reported ocular manifestation in GFAP astrocytopathy, it has not been well-characterized as orbital fat hyperintensity. Here, we report a rare case in which GFAP astrocytopathy initially presented with orbital fat hyperintensity. METHODS: A 26-year-old woman presenting with headache, fever, and bilateral ocular pain was evaluated using neurologic examination, CSF examination, autoantibody testing, and multimodal MRI including orbital conditions. RESULTS: Orbital MRI revealed hyperintensity in the bilateral orbital fat tissue on short tau inversion recovery sequences without optic nerve involvement, whereas intracranial MRI was initially unremarkable. CSF examination showed increase in lymphocytes and was positive for anti-GFAP antibodies. Subsequent MRI revealed characteristic lesions in the thalamic and perivascular area. High-dose corticosteroid therapy led to rapid clinical improvement and resolution of orbital and intracranial MRI lesions. DISCUSSION: This case demonstrates that orbital fat hyperintensity may be an early manifestation of GFAP astrocytopathy, preceding intracranial lesions. Recognition of this orbital MRI finding facilitates earlier diagnosis and treatment, potentially leading to improved prognosis.