Genetic influences on endometriosis in an Australian twin sample. [email protected].

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 rMz = .46+/-.09 and rDz = .28 +/-.13. When available medical and pathology reports were included, they changed to rMz =.52 +/-.08 and rDZ = .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.