Vitamin D receptor rs731236 polymorphism and susceptibility to adolescent idiopathic scoliosis in Brazilian girls

Background The etiology and pathogenesis of adolescent idiopathic scoliosis (AIS) is thought to involve genetic and environmental factors, including low bone mineral density. This study aimed to evaluate the association between vitamin D receptor gene ( VDR ) polymorphism (rs731236, TaqI), curve magnitude, and anthropometric characteristics in girls with AIS. Methods A retrospective case-control study included 175 Brazilian girls with AIS and 175 healthy controls. Genotyping was performed using a validated real-time PCR assay. Associations were evaluated using binary and linear regression models. Results The median Cobb angle was 48.7° (11–110°), the majority ( n = 100, 57.1%) had an indication for surgical treatment (Cobb ≥45°), and 120 (68.6%) were skeletally mature (Risser IV and V). Minor allele frequencies of VDR rs731236 (A > G) polymorphism were 41%, 45%, 38%, and 35.7% for all AIS, Cobb < 45° and Cobb ≥45°, and healthy volunteers, respectively. Among underweight and normal-weight participants, however, the VDR GG genotype was associated with AIS susceptibility compared to healthy controls (OR = 4.4; CI95%=1.01–19.3). A positive correlation was observed between the presence of the VDR GG genotype and an increase in the Cobb angle of 1.2 degrees for every 1 kg/m 2 increase in BMI ( P = 0.035). Conclusion The VDR rs731236 GG genotype was associated with AIS susceptibility among underweight and normal-weight Brazilian girls, suggesting that anthropometric status may modify the phenotypic expression of genetic susceptibility. These findings are hypothesis-generating and require confirmation in larger studies, with control for genetic ancestry, before any clinical application.