A Longitudinal Comparison of Two Autoimmune GFAP Astrocytopathy Cases With Persistent Cognitive Impairment and Divergent Treatment Courses

Background Autoimmune glial fibrillary acidic protein astrocytopathy (GFAP‐A) is an inflammatory neurological disease of the CNS characterized by GFAP antibody positivity. Cognitive impairment is a common feature of this disease; however, its long‐term outcomes remain unclear. Case 1 A 74‐year‐old Japanese man was admitted to our hospital for examination and treatment of progressive cognitive impairment that had developed 9 months before admission. At the time of admission, his FAB score was eight and cerebrospinal fluid (CSF) IgG index was 0.91. The patient tested positive for GFAP antibodies in CSF and was diagnosed with GFAP‐A. Intravenous methylprednisolone (IVMP) was administered 28 days after admission. After treatment, the FAB score improved to 12. However, 117 days after the initial treatment, the cognitive function deteriorated again, requiring another course of IVMP. Despite these treatments, the patient experienced repeated relapses with progressive cognitive decline and brain atrophy. Case 2 A 66‐year‐old man was admitted with cognitive impairment and abnormal behavior that began 60 days prior to admission. His FAB score was six and CSF IgG index was 1.5. After admission, his cognitive function showed slight improvement; however, the CSF IgG index remained high. The diagnosis was confirmed by a positive CSF GFAP antibody test, and IVMP was administered from day 109 after admission. After IVMP treatment, the FAB score improved to 15. Conclusion In patients with GFAP‐A, delayed treatment initiation may result in irreversible cognitive impairment. GFAP‐A should be included in the differential diagnosis of treatable dementia, and early therapeutic intervention is recommended.