title: Growing pains: twin family study evidence for genetic susceptibility and a genetic relationship with restless legs syndrome.
abstract: BACKGROUND
  Growing pains (GP) is a prevalent familial childhood disorder of unknown aetiology. Familial occurrence of GP, and individual and familial association of GP with restless legs syndrome (RLS) has been reported.
  
  
  METHODS
  We applied a twin family design to search for evidence of genetic susceptibility to GP, and for a genetic relationship between GP and RLS. The parents of 1843 twin pairs aged 3-16 years were administered a questionnaire, which identified 88 pairs with at least one twin individual fulfilling criteria for GP. Standard questionnaires for history of GP and RLS were completed for these twin pairs, their siblings and parents.
  
  
  RESULTS
  Twenty-five of 34 monozygotic (MZ) pairs were concordant for GP, compared with 12 of the 54 dizygotic (DZ) pairs. The casewise concordance was 0.85 and 0.36 for MZ and DZ pairs, respectively (p < 0.001). The lifetime GP prevalence for relatives of twins with GP was 51% for non-twin siblings, 47% for parents. Twenty-three percent of twin individuals with GP met RLS criteria compared with 8% of twin individuals without GP (p = 0.03). Of the twins with GP concordance, 19% met RLS criteria compared with 2% of twins with GP discordance (p = 0.01). In two MZ pairs, one had GP and the other RLS. The lifetime prevalence of RLS was 40% for mothers, and 24% for fathers and 18% for non-twin siblings.
  
  
  CONCLUSIONS
  This first twin family study of GP provides evidence for a genetic aetiology and for a genetic relationship to RLS.
authors.affiliation: Department of Anaesthesia and Pain Medicine, Sydney Children's Hospital, Randwick, Australia. dchamp@bigpond.net.au
authors.forename: D
authors.initials: D
authors.lastname: Champion
authors.forename: S
authors.initials: S
authors.lastname: Pathirana
authors.forename: C
authors.initials: C
authors.lastname: Flynn
authors.forename: A
authors.initials: A
authors.lastname: Taylor
authors.forename: J L
authors.initials: JL
authors.lastname: Hopper
authors.forename: S F
authors.initials: SF
authors.lastname: Berkovic
authors.forename: T
authors.initials: T
authors.lastname: Jaaniste
authors.forename: W
authors.initials: W
authors.lastname: Qiu
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D008297:Male; D059352:Musculoskeletal Pain / Q000235:genetics*; D010507:Periodicity; D012148:Restless Legs Syndrome / Q000235:genetics*; D011795:Surveys and Questionnaires; D014429:Twins, Dizygotic / Q000235:genetics*; D014430:Twins, Monozygotic / Q000235:genetics*