FTO and Crouzon syndrome-acanthosis nigricans syndrome: rs12149832 of the FTO gene increased the risk of CAN threefold (OR 3.22(1.04–9.95), p = 0.04), while rs1801282 of the PPARG gene and rs13016963 of the FLACC1 gene increased the risk twofold (OR 2.56(1.19–5.49), p = 0.02) and (OR 2.34(1.00-5.46), p = 0.05) respectively.