Objective:To explore the clinical characteristics and prognoses of severe autoimmune glial fibrillary acidic protein astrocytopathy (GFAP-A).Methods:A retrospective analysis was performed. The clinical data of 12 patients with severe GFAP-A admitted to Department of Neurology, Guangdong 999 Brain Hospital from January 2018 to June 2023 were collected, including demography, clinical manifestations, MRI features, laboratory examination results (such as antibodies), treatments and prognoses.Results:Among the 12 patients, 9 were male and 3 were female, with an average onset age of (46.58±17.53) years. Primary symptoms included headache, limb weakness, limb numbness, mental disorder, epileptic seizure, and urinary and defecation disorder; 9 patients had fever before onset. With aggravated severe GFAP-A, 12 patients had impaired consciousness, 12 had respiratory failure, 6 had unstable blood pressure and heart rate, and 2 had status epilepticus. Cranial MRI indicated abnormal lesions in all 12 patients, including 10 with brainstem involvement (7 had involved medulla oblongata); 10 showed soft meningeal enhancement. In 8 patients received MRI of the whole spinal cord, 7 had abnormal spinal cord lesions; point-like enhancement of the whole spinal meninges was observed in 6 of the 7 patients. All 12 patients had positive cerebrospinal fluid GFAP-IgG, and 3 patients also had positive serum GFAP-IgG. All patients accepted glucocorticoids and immunoglobulin immunotherapy, and 1 patient was supplemented with mycophenolate mofetil; 8 patients had good prognosis, and 4 patients died. Pulmonary infection, hyponatremia, hypoproteinemia, and deep vein thrombosis were the common complications.Conclusion:Patients with severe GFAP-A mainly manifest as meningoencephalitis and meningoencephalomyelitis, and are likely involved medulla oblongata, enjoying rapid clinical progression; even with early immunotherapy, high mortality rate is still noted.