title: Familial occurrence frequencies and relative risks for systemic sclerosis (scleroderma) in three United States cohorts.
abstract: OBJECTIVE
  To determine the frequency with which scleroderma (systemic sclerosis; SSc) recurs in families and the familial relative risk (lambda) in the US.
  
  
  METHODS
  Family histories of SSc were prospectively surveyed in 3 large US cohorts of SSc patients, 2 in Texas and 1 in Michigan. Diagnoses of familial SSc were verified by rheumatologist evaluation and/or review of medical records. Familial relative risks for first-degree relatives (lambda1) and siblings (lambdas) were calculated using actual reported counts of first-degree relatives in 2 cohorts and recent estimates of SSc prevalence in the US.
  
  
  RESULTS
  Compared with the estimated prevalence of SSc in the US (2.6 cases/10,000 population [0.026%]), the disease occurred in 1 or more first-degree relatives in 1.5-1.7% of SSc families in the 3 cohorts (or 11 of 703 families [1.6%]), a significant increase. Familial relative risks in first-degree relatives in the 3 cohorts ranged from 10 to 16 (13 combined), and in siblings they ranged from 10 to 27 (15 combined).
  
  
  CONCLUSIONS
  SSc occurs significantly more frequently in families with scleroderma (1.6%) than in the general population (0.026%). A positive family history of SSc is the strongest risk factor yet identified for SSc; however, the absolute risk for each family member remains quite low (<1%).
authors.affiliation: The University of Texas-Houston Health Science Center, 77030, USA.
authors.forename: F C
authors.initials: FC
authors.lastname: Arnett
authors.forename: M
authors.initials: M
authors.lastname: Cho
authors.forename: S
authors.initials: S
authors.lastname: Chatterjee
authors.forename: M B
authors.initials: MB
authors.lastname: Aguilar
authors.forename: J D
authors.initials: JD
authors.lastname: Reveille
authors.forename: M D
authors.initials: MD
authors.lastname: Mayes
mesh_terms: D044383:Black People / Q000235:genetics; D015331:Cohort Studies; D005192:Family Health; D005260:Female; D020022:Genetic Predisposition to Disease; D006630:Hispanic or Latino / Q000235:genetics; D006801:Humans; D008297:Male; D008824:Michigan / Q000453:epidemiology; D008875:Middle Aged; D009679:Nuclear Family; D012306:Risk; D012595:Scleroderma, Systemic / Q000208:ethnology / Q000235:genetics*; D013781:Texas / Q000453:epidemiology; D044465:White People / Q000235:genetics; D001741:Black or African American