To describe a single-center retrospective cohort of 5 patients with glial fibrillary acidic protein (GFAP) positive antibody.

GFAP astrocytopathy is an inflammatory autoimmune disorder described in 2016 most often characterized by meningoencephalitis though can also involve the spinal cord and optic nerve. The disorder is often monophasic and corticosteroid-responsive, however 20% of patients have a relapsing course necessitating steroid-sparing therapies. Though it is confirmed by presence of CSF GFAP IgG, atypical presentations and possibility of false positives add to the diagnostic challenge.

Retrospective chart review. Demographics, antibody titers, imaging/CSF data, treatment regimens and clinical outcomes were reviewed.

Five patients (mean age: 58, range 35-83) were identified to have positive CSF GFAP antibodies during their presentation. Three patients had the typical presentations of myelitis or meningoencephalomyelitis, one patient had encephalopathy and 1 patient presented with progressive hemiparesis and diagnosed with multiple sclerosis (MS). MRI showed abnormalities in all 5 patients on initial presentation (3/5 showed typical perivascular enhancing lesions in brain or spinal cord, 1 showed extensive demyelinating disease and 1 non-specific white matter changes). CSF GFAP IgG turned negative in 3/5 patients on repeat testing, 2 other patients were not re-tested. None of the patients had serum GFAP-IgG positivity. 3/5 patients had associated low titer GAD65 antibodies. 4 patients received high dose intravenous steroids acutely and then subsequently steroid-sparing therapy with clinical improvement. Only 1 patient had malignancy (vulvar carcinoma). The patient diagnosed with MS was considered a false-positive and the patient with encephalopathy had further cognitive decline and was diagnosed with early Alzheimer’s disease as well.

This retrospective case series highlights possible diagnostic challenges in GFAP astrocytopathy. Patients with typical clinical presentations of meningoencephalomyelitis have favorable clinical response to steroids and steroid sparing therapy. GFAP antibody testing can be associated with low-titer false positives as seen in our cohort.