title: The frequency of autoimmune N-methyl-D-aspartate receptor encephalitis surpasses that of individual viral etiologies in young individuals enrolled in the California Encephalitis Project.
abstract: BACKGROUND
  In 2007, the California Encephalitis Project (CEP), which was established to study the epidemiology of encephalitis, began identifying cases of anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis. Increasing numbers of anti-NMDAR encephalitis cases have been identified at the CEP, and this form rivals commonly known viral etiologies as a causal agent. We report here the relative frequency and differences among encephalitides caused by anti-NMDAR and viral etiologies within the CEP experience.
  
  
  METHODS
  Demographic, frequency, and clinical data from patients with anti-NMDAR encephalitis are compared with those with viral encephalitic agents: enterovirus, herpes simplex virus type 1 (HSV-1), varicella-zoster virus (VZV), and West Nile virus (WNV). All examined cases presented to the CEP between September 2007 and February 2011 and are limited to individuals aged ≤30 years because of the predominance of anti-NMDAR encephalitis in this group. The diagnostic costs incurred in a single case are also included.
  
  
  RESULTS
  Anti-NMDAR encephalitis was identified >4 times as frequently as HSV-1, WNV, or VZV and was the leading entity identified in our cohort. We found that 65% of anti-NMDAR encephalitis occurred in patients aged ≤18 years. This disorder demonstrated a predilection, which was not observed with viral etiologies, for females (P < .01). Seizures, language dysfunction, psychosis, and electroencephalographic abnormalities were significantly more frequent in patients with anti-NMDAR encephalitis (P < .05), and autonomic instability occurred exclusively in this group.
  
  
  CONCLUSIONS
  Anti-NMDAR encephalitis rivals viral etiologies as a cause of encephalitis within the CEP cohort. This entity deserves a prominent place on the encephalitic differential diagnosis to avoid unnecessary diagnostic and treatment costs, and to permit a more timely treatment.
authors.affiliation: Communicable Disease and Emergency Response Branch, Division of Communicable Disease Control, California Department of Public Health, Richmond, CA 94804, USA. ms2gable@yahoo.com
authors.forename: Mary S
authors.initials: MS
authors.lastname: Gable
authors.forename: Heather
authors.initials: H
authors.lastname: Sheriff
authors.forename: Josep
authors.initials: J
authors.lastname: Dalmau
authors.forename: Drake H
authors.initials: DH
authors.lastname: Tilley
authors.forename: Carol A
authors.initials: CA
authors.lastname: Glaser
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D001327:Autoimmune Diseases / Q000453:epidemiology* / Q000473:pathology; D002140:California / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D019411:Clinical Laboratory Techniques / Q000191:economics; D004660:Encephalitis / Q000453:epidemiology* / Q000209:etiology* / Q000473:pathology; D005260:Female; D017048:Health Care Costs / Q000706:statistics & numerical data; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D015995:Prevalence; D016194:Receptors, N-Methyl-D-Aspartate / Q000276:immunology*; D014777:Virus Diseases / Q000175:diagnosis / Q000453:epidemiology* / Q000473:pathology; D055815:Young Adult
chemical_list: D016194:Receptors, N-Methyl-D-Aspartate