title: Phenotypic familial aggregation in chronic chilblains.
abstract: Our clinical observations and two earlier studies indicate familial clustering to be involved in chronic chilblains. Demonstrating phenotypic familial aggregation is a next step to investigate the origin of familial clustering.
  
  
  
  This study was initiated to assess evidence for phenotypic familial aggregation in chronic chilblains.
  
  
  
  Using a case-control family design in a primary care setting, we computed the familial relative risk of at least one episode of chronic chilblains during life with 95% confidence intervals (CIs). The study population consisted of 192 relatives of 31 case probands (at least one confirmed episode of chronic chilblains). The control population consisted of 178 relatives of 31 sex- and age-matched index controls (no history of chronic chilblains).
  
  
  
  The familial relative risk of chronic chilblains was 3.6 (95% CI 1.9-7.3). Additional sensitivity analysis shows similar figures.
  
  
  
  We demonstrate robust phenotypic familial aggregation in chronic chilblains.
authors.affiliation: Department of Primary and Community Care, Unit Sex and Women's Health, Radboud University Medical Center, Internal Post Code 118, PO Box 9101, 6500 HB Nijmegen, The Netherlands, i.souwer@wxs.nl.
authors.forename: Ibo H
authors.initials: IH
authors.lastname: Souwer
authors.affiliation: Department of Primary and Community Care, Radboud University Medical Center, Internal Post Code 117, PO Box 9101, 6500 HB Nijmegen, The Netherlands and.
authors.forename: Deborah
authors.initials: D
authors.lastname: Smaal
authors.affiliation: Department of Primary and Community Care, Radboud University Medical Center, Internal Post Code 117, PO Box 9101, 6500 HB Nijmegen, The Netherlands and.
authors.forename: Jacobus H J
authors.initials: JH
authors.lastname: Bor
authors.affiliation: Department of Medical Genetics, University Medical Center Utrecht, PO Box 85090, 3508 AB Utrecht, The Netherlands.
authors.forename: Nine
authors.initials: N
authors.lastname: Knoers
authors.affiliation: Department of Primary and Community Care, Unit Sex and Women's Health, Radboud University Medical Center, Internal Post Code 118, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
authors.forename: Antoine L M
authors.initials: AL
authors.lastname: Lagro-Janssen
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D002647:Chilblains / Q000175:diagnosis / Q000235:genetics*; D002908:Chronic Disease; D016000:Cluster Analysis; D003080:Cold Temperature / Q000009:adverse effects*; D004198:Disease Susceptibility; D005192:Family Health; D005260:Female; D005820:Genetic Testing; D006801:Humans; D008297:Male; D009426:Netherlands; D010641:Phenotype; D012307:Risk Factors
keywords: Case–control study; chilblains; cold temperature; disease susceptibility; general practice; genetics.