title: Ethnicity, race, and socioeconomic status influence incidence of Langerhans cell histiocytosis.
abstract: BACKGROUND
  Langerhans cell histiocytosis (LCH) is a rare disease, and its etiology is not well understood. Population-based studies may contribute to etiologic research by defining incidence patterns. This study was designed to evaluate the descriptive epidemiology of disseminated LCH in the United States, using data from population-based cancer registries.
  
  
  METHODS
  We analyzed the incidence and survival of disseminated LCH in children and adolescents (0-19 years) from 18 SEER registries during 2000-2009. Age-standardized incidence rates (ASIR) per million and rate ratios (RR) were calculated by gender, race, ethnicity, age, and socioeconomic variables (crowding, rural/urban, education, and poverty) using the SEER*Stat software 8.0.1. Relative survival (RS) estimates were calculated using Ederer II method.
  
  
  RESULTS
  One hundred forty-five cases of disseminated LCH were recorded; ASIR was 0.70/million per year. Lower ASIR was observed for blacks (vs. whites) (RR = 0.41, 95% CI 0.18-0.81), while higher ASIR was noted for Hispanics (vs. non-Hispanics) (RR = 1.63, 95% CI 1.15-2.29). Risk of LCH was higher in crowded counties (RR = 1.84, 95% CI 1.31-2.58) and also in areas with low educational level (RR = 1.49, 95% CI 1.02-2.22). Five-year relative survival was 90.0% (95% CI 83.0-94.2). Important differences in survival were noted according to gender (male: RS = 96.0 vs. female: RS = 83.4%, P = 0.029) and age (<1 year: RS = 78.5, 1-4 years: RS = 95.6%, 5-19 years: RS = 100%, P = 0.004).
  
  
  CONCLUSIONS
  This population-based study shows significant variations in the incidence of disseminated LCH by race and ethnic group, as well as the influence of socioeconomic factors. These data may provide clues to causation and point toward the need for analytical epidemiologic studies.
authors.affiliation: Faculdade de Ciências Médicas da Santa Casa de São Paulo, Department of Social Medicine, São Paulo, Brazil.
authors.forename: Karina Braga
authors.initials: KB
authors.lastname: Ribeiro
authors.forename: Barbara
authors.initials: B
authors.lastname: Degar
authors.forename: Célia Beatriz Gianotti
authors.initials: CB
authors.lastname: Antoneli
authors.forename: Barrett
authors.initials: B
authors.lastname: Rollins
authors.forename: Carlos
authors.initials: C
authors.lastname: Rodriguez-Galindo
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D005260:Female; D006646:Histiocytosis, Langerhans-Cell / Q000453:epidemiology* / Q000208:ethnology / Q000401:mortality; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D012923:Social Class; D014481:United States / Q000453:epidemiology
keywords: children; epidemiology; health disparities; langerhans cell histiocytosis