IL6 and Legg-Calvé-Perthes disease: Recent studies investigating the genetic factors associated with Perthes disease have reported that the vascular endothelial growth factor (VEGF), Hypoxia Inducible Factor 1 (HIF1), and interleukin (IL)-6 are potential contributors to disease development (Kim, 2012; Yamaguchi et al., 2016).