Genetic influences on endometriosis in an Australian twin sample

Objective: To investigate the prevalence of and twin pair concordance for endometriosis. Design: A questionnaire survey incorporating validation. Setting: An Australia-wide volunteer sample of female monozygotic (MZ) and dizygotic (DZ) twin pairs from the Australian National Health and Medical Research Council Twin Register. Patient(s): Twins were selected only on the basis of previous participation in twin research. Intervention(s): Questionnaires were sent to 3,298 individuals. Information was requested from physicians named by consenting twins. Main Outcome Measure(s): Reported endometriosis, validated where possible by pathology or surgical report. Result(s): Three thousand ninety-six (94%) of the twins and 145 (82%) of the physicians responded to the survey. Two hundred fifteen twins reported endometriosis, for a prevalence rate of .07 among question respondents. Tetrachoric twin pair correlations for self-reported endometriosis (MZ: n = 854 and DZ: n = 493) were r(MZ) = .46 +/- .09 and r(DZ) = .28 +/- .13. When available medical and pathology reports were included, they changed to r(MZ) = .52 +/- .08 and r(DZ) = .19 +/- .16, suggesting that 51% of the variance of the latent liability to endometriosis may be attributable to additive genetic influences. Conclusion(s): These findings support the hypothesis that genes influence liability to endometriosis. (C) 1999 by American Society for Reproductive Medicine.