Indeed, the exogenous mutant CRT found at levels observed in MPN patients, acts as a ‘rogue’ cytokine, capable of activating TPO receptor/JAK–STAT signalling in patient primary cells, by binding to the immature N‐glycosylated TPO receptor complexed with mutant endogenous mutant CRT.61 The gene discussed is CALR; the disease is myeloproliferative neoplasm.