Scoliosis in twins. A meta-analysis of the literature and report of six cases.

STUDY DESIGN: This study is a meta-analysis of the world's literature on adolescent idiopathic scoliosis in monozygotic and dizygotic twins. Additionally, six previously unreported cases of scoliosis in twins are presented.

OBJECTIVES: To compare and contrast the concordance, severity, and curve patterns in monozygotic and dizygotic twins with adolescent idiopathic scoliosis in an attempt to document a genetic etiology and delineate inheritance patterns for adolescent idiopathic scoliosis.

SUMMARY OF BACKGROUND DATA: There are numerous case reports of twins sets with adolescent idiopathic scoliosis. However, this data has not been previously analyzed as a single data base.

METHODS: The literature was searched for cases of twins with adolescent idiopathic scoliosis, and six cases of patients treated by authors were added. One hundred cases of sets of twins were discovered, 68 of which had sufficient data for comparative analysis. Each set was evaluated for monozygosity, concordance of scoliosis, curve pattern, and severity of curve.

RESULTS: Thirty-seven sets of twins were monozygous, and 31 sets were dizygous. Concordance was 73% among monozygous twins and 36% among dizygous twins. The difference is statistically significant at P < 0.003. Curve severity could be compared in 20 sets of monozygous twins and 16 sets of dizygous twins. Among monozygous twins, there was a correlation coefficient of r = 0.399 (P < 0.126). Curve pattern comparison was not statistically significant.

CONCLUSIONS: Monozygous twins have a significantly higher rate of concordance than dizygous twins, and the curves in monozygous twins develop and progress together. Based on these data, there is strong evidence for a genetic etiology for adolescent idiopathic scoliosis.