BACKGROUND AND OBJECTIVES: Early recognition of patients with rapidly progressive dementia (RPD) attributed to autoimmune encephalitis (AE) is important because rapid initiation of immunotherapy improves outcomes. However, ancillary testing is often time-consuming because of the broad differential diagnosis, highlighting the need for accurate patient selection based on early clinical features. We aim to determine the frequency of AE subtypes in patients with RPD (AE-RPD) and characterize presenting subphenotypes (i.e., symptoms in addition to dementia) compared with other diagnoses. METHODS: This prospective multicenter observational cohort study was conducted from December 2019 to December 2024 across centers in the Netherlands and included adult patients with RPD, defined as dementia beginning within 1 year of symptom onset. Clinical features and ancillary testing data were collected and reviewed by 3 neurologists. Serum and CSF were evaluated for neuronal/glial autoantibodies. RESULTS: = 0.004). In patients with AE-RPD without seizures, autoimmune glial fibrillary acidic protein (GFAP) astrocytopathy was the most common subtype (8/31; 26%), mostly presenting with prominent psychotic features or movement disorders (both 4/8; 50%). DISCUSSION: In this study, AE was the most common treatment-responsive cause of RPD. Anti-leucine-rich, glioma-inactivated 1 encephalitis and autoimmune GFAP astrocytopathy were the predominant subtypes in AE-RPD.
Steenhoven et al. (Fri,) studied this question.