Genetic factors play an important role in the pathogenesis of both ET and RLS [6–11].Genome wide association study (GWAS) showed that several single nucleotide polymorphisms (SNPs) were associated with the risk of RLS, including MEIS1, BTBD9, PTPRD, MAP2K5, TOX3 and Intergenic region of 2p14 [12–16]. Here, MAP2K5 is linked to essential thrombocythemia.