OBJECTIVE: To investigate the association between calmodulin1 (CALM1) gene or 
estrogen receptor-alpha (ESR1) polymorphisms and double curve of adolescent 
idiopathic scoliosis (AIS).
METHODS: 67 double curve patients (30 degrees < Cobb angle < 90 degrees ), 100 
controls. There were 4 polymorphic loci, rs12885713 (-16C > T) and rs5871 locus 
in CALM1 gene, rs2234693 (PvuII) and rs9340799 (XbaI) in ESR1 gene analyzed 
sequence by ABI3730 genetic analyzer.
RESULTS: There were 60 patients with Cobb angle > or = 40 degrees . According to 
the apical location of major curve, there were 40 thoracic curve patients. 
Furthermore, 1) there are statistical differences on the polymorphic 
distribution of ESR1 gene rs2234693 site between the double curve, Cobb angle > 
or = 40 degrees or thoracic curve patients and the controls, respectively 
(chi(2) = 6.081, 5.554, 6.1935; P = 0.014, 0.0128, 0.0184); 2) between the 
double curve cases and the controls, there is difference on the polymorphic 
distribution of rs12885713 site in CALM1 gene (chi(2) = 4.478; P = 0.034); 3) 
Between the thoracic curve patients and the controls, there is difference on the 
distribution of rs5871 allele polymorphism in CALM1 gene (chi(2) = 6.6061; P = 
0.0102).
CONCLUSION: Double curve patterns might be related to ESR1 gene rs2234693 
(PvuII) site polymorphism. It is necessary to clarify the association between 
the polymorphisms of ESR1 gene and CALM1 gene and different subtypes of 
adolescent idiopathic scoliosis in the further study.