Sibling familial risk ratio of meningococcal disease in UK Caucasians

Abstract

To quantify the host genetic component of meningococcal disease (MD) susceptibility, the sibling risk ratio (λ_s) was calculated as the ratio of observed MD cases among 845 siblings of 443 UK Caucasian cases to that expected, calculated from age-calendar year specific rates for England and Wales. Twenty-seven siblings contracted MD compared with an expected 0·89, generating a λ_s value of 30·3. Overestimation of λ_s due to Neisseria meningitidis exposure was minimized by excluding siblings with MD onset within set time points of the index case. Irrespective of whether siblings contracted MD more than 1, 3, 6, 9 or 12 months after the index case, the λ_s varied slightly (λ_s range: 8·2–11·9), suggesting that host genetic factors may contribute approximately one third of the total λ_s. Social class distribution did not differ between MD cases and the general population of England and Wales. This study is the first to calculate λ_s for MD and establishes that susceptibility to MD has a significant host genetic component.