title: Familiality of kidney stone disease in Iceland.
abstract: OBJECTIVE
  The aetiology of kidney stones is multifactorial, with environmental and genetic factors contributing to the pathogenesis. The aim of this study was to assess the role of genetic factors in kidney stone disease by examining the heritability of the trait in Icelandic patients.
  
  
  METHODS
  Medical records at all major hospitals and imaging centres in Iceland were searched for diagnostic codes indicative of kidney stones, yielding a cohort of 5954 incident patients with kidney stone disease. The list of patients was cross-matched with a genealogy database that covers the entire Icelandic nation. The risk ratio (RR) and kinship coefficient (KC) were calculated to determine the risk of kidney stones in relatives of stone formers and the relatedness among kidney stone patients.
  
  
  RESULTS
  The risk of kidney stones among family members of stone formers was significantly higher than in the general population. In 2959 patients with radiopaque stones, the RR ranged from 2.25 (p<0.001) for first degree relatives of probands (such as parents or siblings) to 1.07 (p<0.01) in fifth degree relatives. Moreover, for confirmed recurrent stone formers the RR of kidney stones in parents and offspring was in excess of 10 (p<0.001). The KC analysis shows that Icelandic patients with kidney stone disease are significantly more related to each other than is the average Icelander, even when considering only relatives separated by four meioses or more (p<0.05).
  
  
  CONCLUSIONS
  The results suggest that genetic factors may substantially influence the risk of kidney stone disease in Iceland.
authors.affiliation: Children's Medical Center, Landspitali University Hospital, Reykjavik, Iceland.
authors.forename: Vidar O
authors.initials: VO
authors.lastname: Edvardsson
authors.forename: Runolfur
authors.initials: R
authors.lastname: Palsson
authors.forename: Olafur S
authors.initials: OS
authors.lastname: Indridason
authors.forename: Sverrir
authors.initials: S
authors.lastname: Thorvaldsson
authors.forename: Kari
authors.initials: K
authors.lastname: Stefansson
mesh_terms: D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D007055:Iceland / Q000453:epidemiology; D007669:Kidney Calculi / Q000453:epidemiology* / Q000235:genetics; D008297:Male; D008875:Middle Aged; D010375:Pedigree; D015995:Prevalence; D011379:Prognosis; D012008:Recurrence; D012189:Retrospective Studies; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors