There were significant differences on time to progression according to molecular classification (20-year probability of disease progression was 44%, 47%, 61%, and 8% in MPN with TP53 disruption, MPN with chromatin or spliceosome mutation, MPN with homozygous JAK2 mutation and MPN with heterozygous JAK2 mutation, respectively, p < 0.001). The gene discussed is JAK2; the disease is myeloproliferative neoplasm.