title: Young-onset dementia: demographic and etiologic characteristics of 235 patients.
abstract: BACKGROUND
  Onset of dementia before age 45 years presents a difficult clinical circumstance, having a broad differential diagnosis and numerous psychosocial implications for the patient and their family. Few data exist regarding the demographics characterizing this population or the etiologic diagnoses among those affected.
  
  
  OBJECTIVE
  To characterize the demographic characteristics and the etiologic causes of dementia with age at onset younger than 45 years.
  
  
  METHODS
  Observational, retrospective, single-cohort study.
  
  
  METHODS
  Multispecialty group academic medical center.
  
  
  METHODS
  We searched the Mayo Clinic Rochester electronic Medical Record Linkage System to identify individuals who were seen for evaluation of progressive cognitive decline between the ages of 17 and 45 years from January 1996 through December 2006. This search identified 235 individuals who met the established inclusion and exclusion criteria.
  
  
  METHODS
  All available clinical, laboratory, magnetic resonance imaging, and pathological data were reviewed.
  
  
  RESULTS
  Causes varied, with neurodegenerative etiologies accounting for 31.1% of the cohort; Alzheimer disease was uncommon. Autoimmune or inflammatory causes accounted for 21.3%. At last follow-up, 44 patients (18.7%) had an unknown etiology, despite exhaustive evaluation. Cause varied with age, with inborn errors of metabolism being more common before age 30 years and with neurodegenerative etiologies being more common after age 35 years.
  
  
  CONCLUSIONS
  Young-onset dementia (age at onset, <45 years) includes a broad variety of etiologies, with few patients having a potentially treatable disorder. The etiologic spectrum and the relative percentages of patients within etiologic groups differed in important ways from existing reports of early-onset dementia (ie, age at onset, <65 years).
authors.affiliation: Department of Neurology, Mayo Clinic, Rochester, MN 55905, USA.
authors.forename: Brendan J
authors.initials: BJ
authors.lastname: Kelley
authors.forename: Bradley F
authors.initials: BF
authors.lastname: Boeve
authors.forename: Keith A
authors.initials: KA
authors.lastname: Josephs
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D017668:Age of Onset; D000544:Alzheimer Disease / Q000453:epidemiology / Q000523:psychology; D001327:Autoimmune Diseases / Q000523:psychology; D015331:Cohort Studies; D003704:Dementia / Q000453:epidemiology* / Q000209:etiology*; D003710:Demography; D005260:Female; D006801:Humans; D015994:Incidence; D007249:Inflammation / Q000453:epidemiology / Q000523:psychology; D008297:Male; D008661:Metabolism, Inborn Errors / Q000453:epidemiology / Q000523:psychology; D008875:Middle Aged; D019636:Neurodegenerative Diseases / Q000523:psychology; D012189:Retrospective Studies; D055815:Young Adult