Growing pains: Twin family study evidence for genetic susceptibility and a genetic relationship with restless legs syndrome

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