title: Epidemiologic study of Langerhans cell histiocytosis in children.
abstract: OBJECTIVE
  The etiology and pathogenesis of Langerhans cell histiocytosis (LCH) remain poorly understood. We conducted an exploratory epidemiologic study to investigate potential risk factors associated with LCH.
  
  
  METHODS
  We used a case-control study design to obtain data from parents of children with LCH (n = 459) who were members of the Histiocytosis Association of America and Canada. The two control groups consisted of 683 community control subjects and 3719 children with childhood cancers treated at participating Children's Cancer Group institutions.
  
  
  RESULTS
  The median age at diagnosis of LCH was 1.8 years (range 0.1 to 14.6 years). Cases were categorized as multisystem LCH (MS-LCH) (n = 208) and single-system LCH (SS-LCH) (n = 198). Statistically significant associations included the following: infections in the neonatal period (MS-LCH, odds ratio (OR) = 2.2), solvent exposure (SS-LCH, OR = 54.9), childhood vaccinations (MS-LCH and SS-LCH, OR = 0.4), thyroid disease in the proband (MS-LCH and SS-LCH, OR = 21.6), and family history of thyroid disease (MS-LCH and SS-LCH, OR = 1.4). The association with thyroid disease in the proband was explained partially by the involvement of the pituitary, with the relative risk decreasing when patients with diabetes insipidus and thyroid involvement were excluded from analysis.
  
  
  CONCLUSIONS
  This large hypothesis-generating study provides directions for future investigations in well-designed population-based or hospital-based epidemiologic studies.
authors.affiliation: Department of Pediatrics, University of Minnesota, Minneapolis 55455, USA.
authors.forename: S
authors.initials: S
authors.lastname: Bhatia
authors.forename: M E
authors.initials: ME
authors.lastname: Nesbit
authors.forename: R M
authors.initials: RM
authors.lastname: Egeler
authors.forename: J D
authors.initials: JD
authors.lastname: Buckley
authors.forename: A
authors.initials: A
authors.lastname: Mertens
authors.forename: L L
authors.initials: LL
authors.lastname: Robison
mesh_terms: D000293:Adolescent; D002170:Canada / Q000453:epidemiology; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D005260:Female; D006646:Histiocytosis, Langerhans-Cell / Q000145:classification / Q000453:epidemiology* / Q000209:etiology; D006801:Humans; D007223:Infant; D008297:Male; D012307:Risk Factors; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires; D014481:United States / Q000453:epidemiology