Recurrent Autoimmune Encephalitis in a Patient With Autoimmune Polyendocrine Syndrome Type 1

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.