Both of these factors have a genetic component [27], [28]: the Danish meta-analysis twin study showed a significant correlation with curve severity in monozygous but not dizygous twins [5], while SNPs in ESR1, ESR2, MATN1 and IGF1 genes are associated with AIS severity [17]–[19], [29]. The gene discussed is ESR1; the disease is androgen insensitivity syndrome.