Due to the large variation in fold change values across MPN subtypes, we analysed the clinical data of MPN patients and observed highly significant increased levels of HTR1B expression in patients who either had at least one episode of major thrombosis (ischemic stroke, deep vein thrombosis with or without pulmonary embolism, splanchnic vein thrombosis) at the time of diagnosis or on the recent history, or showed signs of impaired microcirculation (headache, paresthesia, erythromelalgia) possibly due to microvascular thrombosis, as considered previously.16 Here, HTR1B is linked to pulmonary embolism.