RRAS and Legg-Calve-Perthes disease: In LCPD patients, reduced expression of non-coding RNAs (such as lncRNA n335645) may downregulate the expression of related gene mRNAs (ILK, VCL, RRAS, or other genes), leading to vascular structural or functional damage and interruption of blood supply to the femoral head in LCPD patients (Wang et al., 2022).