Autoimmune polyendocrine syndrome Type 1, also known as autoimmune polyendocrinopathy–candidiasis–ectodermal dystrophy (APS‐1/APECED), is a rare monogenic autoimmune disorder with increasing recognition of neurologic manifestations. We report a critically ill adolescent female with APS‐1 and a prior history of autoimmune encephalitis who presented with acute encephalopathy and seizures. Electroencephalography demonstrated focal seizures superimposed on ictal–interictal continuum activity, and brain MRI revealed cytotoxic lesions of the corpus callosum. High‐titer glutamic acid Decarboxylase 65 (GAD65) antibodies supported a relapse of autoimmune encephalitis after other potential etiologies were excluded. The patient demonstrated marked clinical improvement following aggressive immunotherapy, including plasma exchange, high‐dose corticosteroids, and rituximab. This case highlights the diagnostic and management challenges of autoimmune encephalitis in patients with APS‐1, and to our knowledge, represents the first reported case of recurrent autoimmune encephalitis in this population with a favorable response to early immunomodulatory therapy.
Stemple et al. (2026) studied this question.