RRAS and Legg-Calve-Perthes disease: In LCPD patients, decreased expression of certain lncRNA such as lncRNA n335645 may downregulate the expression of correlating mRNA (ILK, VCL, RRAS, or other genes), thus leading to thus impairing of vascular structure or function and leading to disruption of the blood supply to the femoral head in LCPD patients.