Anti-contactin associated protein like 2 autoimmune encephalitis: A case report and review of the literature

Abstract

BackgroundAutoimmune encephalitis is an insidious neurological disease that can present with an array of neuropsychiatric symptoms. Further classification of autoimmune encephalitis is determined by the presence of unique antibodies such as anti-contactin-associated protein-like-2 (anti-CASPR2). CASPR2 is a voltage gated potassium channel that is found in both the central and peripheral nervous systems and is involved in regulating areas around the nodes of Ranvier. Anti-CASPR2 can also be associated with limbic encephalitis or Morvan syndrome with symptoms ranging from seizures, cerebellar dysfunction, hyper-excitability, dysautonomia, insomnia, neuropathic pain, and weight loss. Case reportA 50-year-old Caucasian female presented to the neurology clinic with a four-month history of acute onset insomnia causing anxiety, poor concentration, memory loss, paranoia, as well as a 13-pound weight loss. She reported a positive antinuclear antibody test two years prior with no established diagnosis. Additionally, a recent thyroid stimulating hormone (TSH) antibody and thyroglobulin antibody screen was found to be negative. Supplementary previous labs determined adrenocorticotropic hormone (ACTH) was within normal limits. She had previously tried a myriad of medications including zolpidem, doxepin, mirtazapine, trazodone, temazepam, eszopiclone, and conjugated estrogen. Constant anxiety forced her to quit both her daily activities and job. Neurologic exam and physical exam revealed no abnormalities. Cerebrospinal fluid analysis (CSF) exhibited an elevated protein of 50.6 mg/dL (normal 15 – 45) and an elevated albumin of 28.1 mg/dL (normal <27.0). A comprehensive autoimmune and paraneoplastic encephalitis panel was performed on serum and CSF, which was positive for CASPR2 (1:10 dilution) antibodies in the serum. The patient was started on a moderate dose of prednisone 20 mg daily for three months and scheduled for monthly infusions of intravenous immunoglobulin (IVIG) 1g/kg body weight for one year. Evaluation of paraneoplastic syndrome by a CT of the chest, abdomen, and pelvis with and without contrast revealed no abnormalities. The patient's insomnia began to improve after initiation of the corticosteroids and was scheduled to continue with the IVIG infusions and prednisone. She reports an improvement with mood and has resumed her job as an exercise instructor as well as daily activities. ConclusionsThis case report examines the presentation and workup of a 50-year-old female with a four-month history of acute onset insomnia and mood disturbances. She was seen by primary care, sleep medicine, psychiatry, and endocrinology before arriving at the neurology clinic where we discovered anti-CASPR2 antibodies in her serum, suggestive of autoimmune encephalitis. This case review examines the current literature regarding autoimmune encephalitis with CASPR2 antibodies and attempts to elucidate the delay in treatment for patients presenting with acute or subacute onset mood disturbances with insomnia.