The mutational landscape associated with progression to BP-MPN is well-described, with frequent presence of multiple ‘high-risk’ mutations that are associated with a poor prognosis in chronic phase MPN, including ASXL1, IDH1/2, RAS, RUNX1, spliceosome mutations and a particularly high incidence of TP53 pathway alterations5,7. Here, ASXL1 is linked to myeloproliferative disorder.