Since the bulk of the population-level predisposition to JAK2V617F positive MPN is likely to be accounted for by variation at JAK2 and TERT, the initial aim of this study is to identify additional germline variants that predispose to JAK2V617F-negative ET or PMF by performing a genome-wide association study (GWAS). This evidence concerns the gene TERT and essential thrombocythemia.