NOS1 and essential thrombocythemia: This is the first study demonstrating a possible association of IL1B rs1143633 with ET in Chinese population, among 12 SNPs harbored in seven possible RLS genes loci, including HMOX1, HMOX2, VDR, IL17A, IL1B, NOS1 and ADH1B. In further subgroup analysis to exclude gender confounders, the significance still remained in both male and female cohort when only ET patients without RLS were included.